Source file src/cmd/go/internal/modload/init.go

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package modload
     6  
     7  import (
     8  	"bytes"
     9  	"context"
    10  	"errors"
    11  	"fmt"
    12  	"internal/godebugs"
    13  	"internal/lazyregexp"
    14  	"io"
    15  	"maps"
    16  	"os"
    17  	"path"
    18  	"path/filepath"
    19  	"slices"
    20  	"strconv"
    21  	"strings"
    22  	"sync"
    23  
    24  	"cmd/go/internal/base"
    25  	"cmd/go/internal/cfg"
    26  	"cmd/go/internal/fips140"
    27  	"cmd/go/internal/fsys"
    28  	"cmd/go/internal/gover"
    29  	"cmd/go/internal/lockedfile"
    30  	"cmd/go/internal/modfetch"
    31  	"cmd/go/internal/search"
    32  
    33  	"golang.org/x/mod/modfile"
    34  	"golang.org/x/mod/module"
    35  )
    36  
    37  // Variables set by other packages.
    38  //
    39  // TODO(#40775): See if these can be plumbed as explicit parameters.
    40  var (
    41  	// ExplicitWriteGoMod prevents LoadPackages, ListModules, and other functions
    42  	// from updating go.mod and go.sum or reporting errors when updates are
    43  	// needed. A package should set this if it would cause go.mod to be written
    44  	// multiple times (for example, 'go get' calls LoadPackages multiple times) or
    45  	// if it needs some other operation to be successful before go.mod and go.sum
    46  	// can be written (for example, 'go mod download' must download modules before
    47  	// adding sums to go.sum). Packages that set this are responsible for calling
    48  	// WriteGoMod explicitly.
    49  	ExplicitWriteGoMod bool
    50  )
    51  
    52  // Variables set in Init.
    53  var (
    54  	gopath string
    55  )
    56  
    57  // EnterModule resets MainModules and requirements to refer to just this one module.
    58  func EnterModule(loaderstate *State, ctx context.Context, enterModroot string) {
    59  	loaderstate.MainModules = nil // reset MainModules
    60  	loaderstate.requirements = nil
    61  	loaderstate.workFilePath = "" // Force module mode
    62  	loaderstate.Fetcher().Reset()
    63  
    64  	loaderstate.modRoots = []string{enterModroot}
    65  	LoadModFile(loaderstate, ctx)
    66  }
    67  
    68  // EnterWorkspace enters workspace mode from module mode, applying the updated requirements to the main
    69  // module to that module in the workspace. There should be no calls to any of the exported
    70  // functions of the modload package running concurrently with a call to EnterWorkspace as
    71  // EnterWorkspace will modify the global state they depend on in a non-thread-safe way.
    72  func EnterWorkspace(loaderstate *State, ctx context.Context) (exit func(), err error) {
    73  	// Find the identity of the main module that will be updated before we reset modload state.
    74  	mm := loaderstate.MainModules.mustGetSingleMainModule(loaderstate)
    75  	// Get the updated modfile we will use for that module.
    76  	_, _, updatedmodfile, err := UpdateGoModFromReqs(loaderstate, ctx, WriteOpts{})
    77  	if err != nil {
    78  		return nil, err
    79  	}
    80  
    81  	// Reset the state to a clean state.
    82  	oldstate := loaderstate.setState(NewState())
    83  	loaderstate.ForceUseModules = true
    84  
    85  	// Load in workspace mode.
    86  	loaderstate.InitWorkfile()
    87  	LoadModFile(loaderstate, ctx)
    88  
    89  	// Update the content of the previous main module, and recompute the requirements.
    90  	*loaderstate.MainModules.ModFile(mm) = *updatedmodfile
    91  	loaderstate.requirements = requirementsFromModFiles(loaderstate, ctx, loaderstate.MainModules.workFile, slices.Collect(maps.Values(loaderstate.MainModules.modFiles)), nil)
    92  
    93  	return func() {
    94  		loaderstate.setState(oldstate)
    95  	}, nil
    96  }
    97  
    98  type MainModuleSet struct {
    99  	// versions are the module.Version values of each of the main modules.
   100  	// For each of them, the Path fields are ordinary module paths and the Version
   101  	// fields are empty strings.
   102  	// versions is clipped (len=cap).
   103  	versions []module.Version
   104  
   105  	// modRoot maps each module in versions to its absolute filesystem path.
   106  	modRoot map[module.Version]string
   107  
   108  	// pathPrefix is the path prefix for packages in the module, without a trailing
   109  	// slash. For most modules, pathPrefix is just version.Path, but the
   110  	// standard-library module "std" has an empty prefix.
   111  	pathPrefix map[module.Version]string
   112  
   113  	// inGorootSrc caches whether modRoot is within GOROOT/src.
   114  	// The "std" module is special within GOROOT/src, but not otherwise.
   115  	inGorootSrc map[module.Version]bool
   116  
   117  	modFiles map[module.Version]*modfile.File
   118  
   119  	tools map[string]bool
   120  
   121  	modContainingCWD module.Version
   122  
   123  	workFile *modfile.WorkFile
   124  
   125  	workFileReplaceMap map[module.Version]module.Version
   126  	// highest replaced version of each module path; empty string for wildcard-only replacements
   127  	highestReplaced map[string]string
   128  
   129  	indexMu sync.RWMutex
   130  	indices map[module.Version]*modFileIndex
   131  }
   132  
   133  func (mms *MainModuleSet) PathPrefix(m module.Version) string {
   134  	return mms.pathPrefix[m]
   135  }
   136  
   137  // Versions returns the module.Version values of each of the main modules.
   138  // For each of them, the Path fields are ordinary module paths and the Version
   139  // fields are empty strings.
   140  // Callers should not modify the returned slice.
   141  func (mms *MainModuleSet) Versions() []module.Version {
   142  	if mms == nil {
   143  		return nil
   144  	}
   145  	return mms.versions
   146  }
   147  
   148  // Tools returns the tools defined by all the main modules.
   149  // The key is the absolute package path of the tool.
   150  func (mms *MainModuleSet) Tools() map[string]bool {
   151  	if mms == nil {
   152  		return nil
   153  	}
   154  	return mms.tools
   155  }
   156  
   157  func (mms *MainModuleSet) Contains(path string) bool {
   158  	if mms == nil {
   159  		return false
   160  	}
   161  	for _, v := range mms.versions {
   162  		if v.Path == path {
   163  			return true
   164  		}
   165  	}
   166  	return false
   167  }
   168  
   169  func (mms *MainModuleSet) ModRoot(m module.Version) string {
   170  	if mms == nil {
   171  		return ""
   172  	}
   173  	return mms.modRoot[m]
   174  }
   175  
   176  func (mms *MainModuleSet) InGorootSrc(m module.Version) bool {
   177  	if mms == nil {
   178  		return false
   179  	}
   180  	return mms.inGorootSrc[m]
   181  }
   182  
   183  func (mms *MainModuleSet) mustGetSingleMainModule(loaderstate *State) module.Version {
   184  	mm, err := mms.getSingleMainModule(loaderstate)
   185  	if err != nil {
   186  		panic(err)
   187  	}
   188  	return mm
   189  }
   190  
   191  func (mms *MainModuleSet) getSingleMainModule(loaderstate *State) (module.Version, error) {
   192  	if mms == nil || len(mms.versions) == 0 {
   193  		return module.Version{}, errors.New("internal error: mustGetSingleMainModule called in context with no main modules")
   194  	}
   195  	if len(mms.versions) != 1 {
   196  		if loaderstate.inWorkspaceMode() {
   197  			return module.Version{}, errors.New("internal error: mustGetSingleMainModule called in workspace mode")
   198  		} else {
   199  			return module.Version{}, errors.New("internal error: multiple main modules present outside of workspace mode")
   200  		}
   201  	}
   202  	return mms.versions[0], nil
   203  }
   204  
   205  func (mms *MainModuleSet) GetSingleIndexOrNil(loaderstate *State) *modFileIndex {
   206  	if mms == nil {
   207  		return nil
   208  	}
   209  	if len(mms.versions) == 0 {
   210  		return nil
   211  	}
   212  	return mms.indices[mms.mustGetSingleMainModule(loaderstate)]
   213  }
   214  
   215  func (mms *MainModuleSet) Index(m module.Version) *modFileIndex {
   216  	mms.indexMu.RLock()
   217  	defer mms.indexMu.RUnlock()
   218  	return mms.indices[m]
   219  }
   220  
   221  func (mms *MainModuleSet) SetIndex(m module.Version, index *modFileIndex) {
   222  	mms.indexMu.Lock()
   223  	defer mms.indexMu.Unlock()
   224  	mms.indices[m] = index
   225  }
   226  
   227  func (mms *MainModuleSet) ModFile(m module.Version) *modfile.File {
   228  	return mms.modFiles[m]
   229  }
   230  
   231  func (mms *MainModuleSet) WorkFile() *modfile.WorkFile {
   232  	return mms.workFile
   233  }
   234  
   235  func (mms *MainModuleSet) Len() int {
   236  	if mms == nil {
   237  		return 0
   238  	}
   239  	return len(mms.versions)
   240  }
   241  
   242  // ModContainingCWD returns the main module containing the working directory,
   243  // or module.Version{} if none of the main modules contain the working
   244  // directory.
   245  func (mms *MainModuleSet) ModContainingCWD() module.Version {
   246  	return mms.modContainingCWD
   247  }
   248  
   249  func (mms *MainModuleSet) HighestReplaced() map[string]string {
   250  	return mms.highestReplaced
   251  }
   252  
   253  // GoVersion returns the go version set on the single module, in module mode,
   254  // or the go.work file in workspace mode.
   255  func (mms *MainModuleSet) GoVersion(loaderstate *State) string {
   256  	if loaderstate.inWorkspaceMode() {
   257  		return gover.FromGoWork(mms.workFile)
   258  	}
   259  	if mms != nil && len(mms.versions) == 1 {
   260  		f := mms.ModFile(mms.mustGetSingleMainModule(loaderstate))
   261  		if f == nil {
   262  			// Special case: we are outside a module, like 'go run x.go'.
   263  			// Assume the local Go version.
   264  			// TODO(#49228): Clean this up; see loadModFile.
   265  			return gover.Local()
   266  		}
   267  		return gover.FromGoMod(f)
   268  	}
   269  	return gover.DefaultGoModVersion
   270  }
   271  
   272  // Godebugs returns the godebug lines set on the single module, in module mode,
   273  // or on the go.work file in workspace mode.
   274  // The caller must not modify the result.
   275  func (mms *MainModuleSet) Godebugs(loaderstate *State) []*modfile.Godebug {
   276  	if loaderstate.inWorkspaceMode() {
   277  		if mms.workFile != nil {
   278  			return mms.workFile.Godebug
   279  		}
   280  		return nil
   281  	}
   282  	if mms != nil && len(mms.versions) == 1 {
   283  		f := mms.ModFile(mms.mustGetSingleMainModule(loaderstate))
   284  		if f == nil {
   285  			// Special case: we are outside a module, like 'go run x.go'.
   286  			return nil
   287  		}
   288  		return f.Godebug
   289  	}
   290  	return nil
   291  }
   292  
   293  func (mms *MainModuleSet) WorkFileReplaceMap() map[module.Version]module.Version {
   294  	return mms.workFileReplaceMap
   295  }
   296  
   297  type Root int
   298  
   299  const (
   300  	// AutoRoot is the default for most commands. modload.Init will look for
   301  	// a go.mod file in the current directory or any parent. If none is found,
   302  	// modules may be disabled (GO111MODULE=auto) or commands may run in a
   303  	// limited module mode.
   304  	AutoRoot Root = iota
   305  
   306  	// NoRoot is used for commands that run in module mode and ignore any go.mod
   307  	// file the current directory or in parent directories.
   308  	NoRoot
   309  
   310  	// NeedRoot is used for commands that must run in module mode and don't
   311  	// make sense without a main module.
   312  	NeedRoot
   313  )
   314  
   315  // ModFile returns the parsed go.mod file.
   316  //
   317  // Note that after calling LoadPackages or LoadModGraph,
   318  // the require statements in the modfile.File are no longer
   319  // the source of truth and will be ignored: edits made directly
   320  // will be lost at the next call to WriteGoMod.
   321  // To make permanent changes to the require statements
   322  // in go.mod, edit it before loading.
   323  func ModFile(loaderstate *State) *modfile.File {
   324  	Init(loaderstate)
   325  	modFile := loaderstate.MainModules.ModFile(loaderstate.MainModules.mustGetSingleMainModule(loaderstate))
   326  	if modFile == nil {
   327  		die(loaderstate)
   328  	}
   329  	return modFile
   330  }
   331  
   332  func BinDir(loaderstate *State) string {
   333  	Init(loaderstate)
   334  	if cfg.GOBIN != "" {
   335  		return cfg.GOBIN
   336  	}
   337  	if gopath == "" {
   338  		return ""
   339  	}
   340  	return filepath.Join(gopath, "bin")
   341  }
   342  
   343  // InitWorkfile initializes the workFilePath variable for commands that
   344  // operate in workspace mode. It should not be called by other commands,
   345  // for example 'go mod tidy', that don't operate in workspace mode.
   346  func (loaderstate *State) InitWorkfile() {
   347  	// Initialize fsys early because we need overlay to read go.work file.
   348  	fips140.Init()
   349  	if err := fsys.Init(); err != nil {
   350  		base.Fatal(err)
   351  	}
   352  	loaderstate.workFilePath = loaderstate.FindGoWork(base.Cwd())
   353  }
   354  
   355  // FindGoWork returns the name of the go.work file for this command,
   356  // or the empty string if there isn't one.
   357  // Most code should use Init and Enabled rather than use this directly.
   358  // It is exported mainly for Go toolchain switching, which must process
   359  // the go.work very early at startup.
   360  func (loaderstate *State) FindGoWork(wd string) string {
   361  	if loaderstate.RootMode == NoRoot {
   362  		return ""
   363  	}
   364  
   365  	switch gowork := cfg.Getenv("GOWORK"); gowork {
   366  	case "off":
   367  		return ""
   368  	case "", "auto":
   369  		return findWorkspaceFile(wd)
   370  	default:
   371  		if !filepath.IsAbs(gowork) {
   372  			base.Fatalf("go: invalid GOWORK: not an absolute path")
   373  		}
   374  		return gowork
   375  	}
   376  }
   377  
   378  // WorkFilePath returns the absolute path of the go.work file, or "" if not in
   379  // workspace mode. WorkFilePath must be called after InitWorkfile.
   380  func WorkFilePath(loaderstate *State) string {
   381  	return loaderstate.workFilePath
   382  }
   383  
   384  // Reset clears all the initialized, cached state about the use of modules,
   385  // so that we can start over.
   386  func (s *State) Reset() {
   387  	s.setState(NewState())
   388  }
   389  
   390  func (s *State) setState(new *State) (old *State) {
   391  	old = &State{
   392  		initialized:     s.initialized,
   393  		ForceUseModules: s.ForceUseModules,
   394  		RootMode:        s.RootMode,
   395  		modRoots:        s.modRoots,
   396  		modulesEnabled:  cfg.ModulesEnabled,
   397  		MainModules:     s.MainModules,
   398  		requirements:    s.requirements,
   399  		workFilePath:    s.workFilePath,
   400  		fetcher:         s.fetcher,
   401  	}
   402  	s.initialized = new.initialized
   403  	s.ForceUseModules = new.ForceUseModules
   404  	s.RootMode = new.RootMode
   405  	s.modRoots = new.modRoots
   406  	cfg.ModulesEnabled = new.modulesEnabled
   407  	s.MainModules = new.MainModules
   408  	s.requirements = new.requirements
   409  	s.workFilePath = new.workFilePath
   410  	// The modfetch package's global state is used to compute
   411  	// the go.sum file, so save and restore it along with the
   412  	// modload state.
   413  	old.fetcher = s.fetcher.SetState(new.fetcher)
   414  
   415  	return old
   416  }
   417  
   418  type State struct {
   419  	initialized               bool
   420  	allowMissingModuleImports bool
   421  
   422  	// ForceUseModules may be set to force modules to be enabled when
   423  	// GO111MODULE=auto or to report an error when GO111MODULE=off.
   424  	ForceUseModules bool
   425  
   426  	// RootMode determines whether a module root is needed.
   427  	RootMode Root
   428  
   429  	// These are primarily used to initialize the MainModules, and should
   430  	// be eventually superseded by them but are still used in cases where
   431  	// the module roots are required but MainModules has not been
   432  	// initialized yet. Set to the modRoots of the main modules.
   433  	// modRoots != nil implies len(modRoots) > 0
   434  	modRoots       []string
   435  	modulesEnabled bool
   436  	MainModules    *MainModuleSet
   437  
   438  	// requirements is the requirement graph for the main module.
   439  	//
   440  	// It is always non-nil if the main module's go.mod file has been
   441  	// loaded.
   442  	//
   443  	// This variable should only be read from the loadModFile
   444  	// function, and should only be written in the loadModFile and
   445  	// commitRequirements functions.  All other functions that need or
   446  	// produce a *Requirements should accept and/or return an explicit
   447  	// parameter.
   448  	requirements *Requirements
   449  
   450  	// Set to the path to the go.work file, or "" if workspace mode is
   451  	// disabled
   452  	workFilePath string
   453  	fetcher      *modfetch.Fetcher
   454  }
   455  
   456  func NewState() *State {
   457  	s := new(State)
   458  	s.fetcher = modfetch.NewFetcher()
   459  	return s
   460  }
   461  
   462  func (s *State) Fetcher() *modfetch.Fetcher {
   463  	return s.fetcher
   464  }
   465  
   466  // Init determines whether module mode is enabled, locates the root of the
   467  // current module (if any), sets environment variables for Git subprocesses, and
   468  // configures the cfg, codehost, load, modfetch, and search packages for use
   469  // with modules.
   470  func Init(loaderstate *State) {
   471  	if loaderstate.initialized {
   472  		return
   473  	}
   474  	loaderstate.initialized = true
   475  
   476  	fips140.Init()
   477  
   478  	// Keep in sync with WillBeEnabled. We perform extra validation here, and
   479  	// there are lots of diagnostics and side effects, so we can't use
   480  	// WillBeEnabled directly.
   481  	var mustUseModules bool
   482  	env := cfg.Getenv("GO111MODULE")
   483  	switch env {
   484  	default:
   485  		base.Fatalf("go: unknown environment setting GO111MODULE=%s", env)
   486  	case "auto":
   487  		mustUseModules = loaderstate.ForceUseModules
   488  	case "on", "":
   489  		mustUseModules = true
   490  	case "off":
   491  		if loaderstate.ForceUseModules {
   492  			base.Fatalf("go: modules disabled by GO111MODULE=off; see 'go help modules'")
   493  		}
   494  		mustUseModules = false
   495  		return
   496  	}
   497  
   498  	if err := fsys.Init(); err != nil {
   499  		base.Fatal(err)
   500  	}
   501  
   502  	// Disable any prompting for passwords by Git.
   503  	// Only has an effect for 2.3.0 or later, but avoiding
   504  	// the prompt in earlier versions is just too hard.
   505  	// If user has explicitly set GIT_TERMINAL_PROMPT=1, keep
   506  	// prompting.
   507  	// See golang.org/issue/9341 and golang.org/issue/12706.
   508  	if os.Getenv("GIT_TERMINAL_PROMPT") == "" {
   509  		os.Setenv("GIT_TERMINAL_PROMPT", "0")
   510  	}
   511  
   512  	if os.Getenv("GCM_INTERACTIVE") == "" {
   513  		os.Setenv("GCM_INTERACTIVE", "never")
   514  	}
   515  	if loaderstate.modRoots != nil {
   516  		// modRoot set before Init was called ("go mod init" does this).
   517  		// No need to search for go.mod.
   518  	} else if loaderstate.RootMode == NoRoot {
   519  		if cfg.ModFile != "" && !base.InGOFLAGS("-modfile") {
   520  			base.Fatalf("go: -modfile cannot be used with commands that ignore the current module")
   521  		}
   522  		loaderstate.modRoots = nil
   523  	} else if loaderstate.workFilePath != "" {
   524  		// We're in workspace mode, which implies module mode.
   525  		if cfg.ModFile != "" {
   526  			base.Fatalf("go: -modfile cannot be used in workspace mode")
   527  		}
   528  	} else {
   529  		if modRoot := findModuleRoot(base.Cwd()); modRoot == "" {
   530  			if cfg.ModFile != "" {
   531  				base.Fatalf("go: cannot find main module, but -modfile was set.\n\t-modfile cannot be used to set the module root directory.")
   532  			}
   533  			if loaderstate.RootMode == NeedRoot {
   534  				base.Fatal(NewNoMainModulesError(loaderstate))
   535  			}
   536  			if !mustUseModules {
   537  				// GO111MODULE is 'auto', and we can't find a module root.
   538  				// Stay in GOPATH mode.
   539  				return
   540  			}
   541  		} else if search.InDir(modRoot, os.TempDir()) == "." {
   542  			// If you create /tmp/go.mod for experimenting,
   543  			// then any tests that create work directories under /tmp
   544  			// will find it and get modules when they're not expecting them.
   545  			// It's a bit of a peculiar thing to disallow but quite mysterious
   546  			// when it happens. See golang.org/issue/26708.
   547  			fmt.Fprintf(os.Stderr, "go: warning: ignoring go.mod in system temp root %v\n", os.TempDir())
   548  			if loaderstate.RootMode == NeedRoot {
   549  				base.Fatal(NewNoMainModulesError(loaderstate))
   550  			}
   551  			if !mustUseModules {
   552  				return
   553  			}
   554  		} else {
   555  			loaderstate.modRoots = []string{modRoot}
   556  		}
   557  	}
   558  	if cfg.ModFile != "" && !strings.HasSuffix(cfg.ModFile, ".mod") {
   559  		base.Fatalf("go: -modfile=%s: file does not have .mod extension", cfg.ModFile)
   560  	}
   561  
   562  	// We're in module mode. Set any global variables that need to be set.
   563  	cfg.ModulesEnabled = true
   564  	setDefaultBuildMod(loaderstate)
   565  	list := filepath.SplitList(cfg.BuildContext.GOPATH)
   566  	if len(list) > 0 && list[0] != "" {
   567  		gopath = list[0]
   568  		if _, err := fsys.Stat(filepath.Join(gopath, "go.mod")); err == nil {
   569  			fmt.Fprintf(os.Stderr, "go: warning: ignoring go.mod in $GOPATH %v\n", gopath)
   570  			if loaderstate.RootMode == NeedRoot {
   571  				base.Fatal(NewNoMainModulesError(loaderstate))
   572  			}
   573  			if !mustUseModules {
   574  				return
   575  			}
   576  		}
   577  	}
   578  }
   579  
   580  // WillBeEnabled checks whether modules should be enabled but does not
   581  // initialize modules by installing hooks. If Init has already been called,
   582  // WillBeEnabled returns the same result as Enabled.
   583  //
   584  // This function is needed to break a cycle. The main package needs to know
   585  // whether modules are enabled in order to install the module or GOPATH version
   586  // of 'go get', but Init reads the -modfile flag in 'go get', so it shouldn't
   587  // be called until the command is installed and flags are parsed. Instead of
   588  // calling Init and Enabled, the main package can call this function.
   589  func (loaderstate *State) WillBeEnabled() bool {
   590  	if loaderstate.modRoots != nil || cfg.ModulesEnabled {
   591  		// Already enabled.
   592  		return true
   593  	}
   594  	if loaderstate.initialized {
   595  		// Initialized, not enabled.
   596  		return false
   597  	}
   598  
   599  	// Keep in sync with Init. Init does extra validation and prints warnings or
   600  	// exits, so it can't call this function directly.
   601  	env := cfg.Getenv("GO111MODULE")
   602  	switch env {
   603  	case "on", "":
   604  		return true
   605  	case "auto":
   606  		break
   607  	default:
   608  		return false
   609  	}
   610  
   611  	return FindGoMod(base.Cwd()) != ""
   612  }
   613  
   614  // FindGoMod returns the name of the go.mod file for this command,
   615  // or the empty string if there isn't one.
   616  // Most code should use Init and Enabled rather than use this directly.
   617  // It is exported mainly for Go toolchain switching, which must process
   618  // the go.mod very early at startup.
   619  func FindGoMod(wd string) string {
   620  	modRoot := findModuleRoot(wd)
   621  	if modRoot == "" {
   622  		// GO111MODULE is 'auto', and we can't find a module root.
   623  		// Stay in GOPATH mode.
   624  		return ""
   625  	}
   626  	if search.InDir(modRoot, os.TempDir()) == "." {
   627  		// If you create /tmp/go.mod for experimenting,
   628  		// then any tests that create work directories under /tmp
   629  		// will find it and get modules when they're not expecting them.
   630  		// It's a bit of a peculiar thing to disallow but quite mysterious
   631  		// when it happens. See golang.org/issue/26708.
   632  		return ""
   633  	}
   634  	return filepath.Join(modRoot, "go.mod")
   635  }
   636  
   637  // Enabled reports whether modules are (or must be) enabled.
   638  // If modules are enabled but there is no main module, Enabled returns true
   639  // and then the first use of module information will call die
   640  // (usually through MustModRoot).
   641  func (loaderstate *State) Enabled() bool {
   642  	Init(loaderstate)
   643  	return loaderstate.modRoots != nil || cfg.ModulesEnabled
   644  }
   645  
   646  func (s *State) vendorDir() (string, error) {
   647  	if s.inWorkspaceMode() {
   648  		return filepath.Join(filepath.Dir(WorkFilePath(s)), "vendor"), nil
   649  	}
   650  	mainModule, err := s.MainModules.getSingleMainModule(s)
   651  	if err != nil {
   652  		return "", err
   653  	}
   654  	// Even if -mod=vendor, we could be operating with no mod root (and thus no
   655  	// vendor directory). As long as there are no dependencies that is expected
   656  	// to work. See script/vendor_outside_module.txt.
   657  	modRoot := s.MainModules.ModRoot(mainModule)
   658  	if modRoot == "" {
   659  		return "", errors.New("vendor directory does not exist when in single module mode outside of a module")
   660  	}
   661  	return filepath.Join(modRoot, "vendor"), nil
   662  }
   663  
   664  func (s *State) VendorDirOrEmpty() string {
   665  	dir, err := s.vendorDir()
   666  	if err != nil {
   667  		return ""
   668  	}
   669  	return dir
   670  }
   671  
   672  func VendorDir(loaderstate *State) string {
   673  	dir, err := loaderstate.vendorDir()
   674  	if err != nil {
   675  		panic(err)
   676  	}
   677  	return dir
   678  }
   679  
   680  func (loaderstate *State) inWorkspaceMode() bool {
   681  	if !loaderstate.initialized {
   682  		panic("inWorkspaceMode called before modload.Init called")
   683  	}
   684  	if !loaderstate.Enabled() {
   685  		return false
   686  	}
   687  	return loaderstate.workFilePath != ""
   688  }
   689  
   690  // HasModRoot reports whether a main module or main modules are present.
   691  // HasModRoot may return false even if Enabled returns true: for example, 'get'
   692  // does not require a main module.
   693  func (loaderstate *State) HasModRoot() bool {
   694  	Init(loaderstate)
   695  	return loaderstate.modRoots != nil
   696  }
   697  
   698  // MustHaveModRoot checks that a main module or main modules are present,
   699  // and calls base.Fatalf if there are no main modules.
   700  func (loaderstate *State) MustHaveModRoot() {
   701  	Init(loaderstate)
   702  	if !loaderstate.HasModRoot() {
   703  		die(loaderstate)
   704  	}
   705  }
   706  
   707  // ModFilePath returns the path that would be used for the go.mod
   708  // file, if in module mode. ModFilePath calls base.Fatalf if there is no main
   709  // module, even if -modfile is set.
   710  func (loaderstate *State) ModFilePath() string {
   711  	loaderstate.MustHaveModRoot()
   712  	return modFilePath(findModuleRoot(base.Cwd()))
   713  }
   714  
   715  func modFilePath(modRoot string) string {
   716  	// TODO(matloob): This seems incompatible with workspaces
   717  	// (unless the user's intention is to replace all workspace modules' modfiles?).
   718  	// Should we produce an error in workspace mode if cfg.ModFile is set?
   719  	if cfg.ModFile != "" {
   720  		return cfg.ModFile
   721  	}
   722  	return filepath.Join(modRoot, "go.mod")
   723  }
   724  
   725  func die(loaderstate *State) {
   726  	if cfg.Getenv("GO111MODULE") == "off" {
   727  		base.Fatalf("go: modules disabled by GO111MODULE=off; see 'go help modules'")
   728  	}
   729  	if !loaderstate.inWorkspaceMode() {
   730  		if dir, name := findAltConfig(base.Cwd()); dir != "" {
   731  			rel, err := filepath.Rel(base.Cwd(), dir)
   732  			if err != nil {
   733  				rel = dir
   734  			}
   735  			cdCmd := ""
   736  			if rel != "." {
   737  				cdCmd = fmt.Sprintf("cd %s && ", rel)
   738  			}
   739  			base.Fatalf("go: cannot find main module, but found %s in %s\n\tto create a module there, run:\n\t%sgo mod init", name, dir, cdCmd)
   740  		}
   741  	}
   742  	base.Fatal(NewNoMainModulesError(loaderstate))
   743  }
   744  
   745  var ErrNoModRoot = errors.New("no module root")
   746  
   747  // noMainModulesError returns the appropriate error if there is no main module or
   748  // main modules depending on whether the go command is in workspace mode.
   749  type noMainModulesError struct {
   750  	inWorkspaceMode bool
   751  }
   752  
   753  func (e noMainModulesError) Error() string {
   754  	if e.inWorkspaceMode {
   755  		return "no modules were found in the current workspace; see 'go help work'"
   756  	}
   757  	return "go.mod file not found in current directory or any parent directory; see 'go help modules'"
   758  }
   759  
   760  func (e noMainModulesError) Unwrap() error {
   761  	return ErrNoModRoot
   762  }
   763  
   764  func NewNoMainModulesError(s *State) noMainModulesError {
   765  	return noMainModulesError{
   766  		inWorkspaceMode: s.inWorkspaceMode(),
   767  	}
   768  }
   769  
   770  type goModDirtyError struct{}
   771  
   772  func (goModDirtyError) Error() string {
   773  	if cfg.BuildModExplicit {
   774  		return fmt.Sprintf("updates to go.mod needed, disabled by -mod=%v; to update it:\n\tgo mod tidy", cfg.BuildMod)
   775  	}
   776  	if cfg.BuildModReason != "" {
   777  		return fmt.Sprintf("updates to go.mod needed, disabled by -mod=%s\n\t(%s)\n\tto update it:\n\tgo mod tidy", cfg.BuildMod, cfg.BuildModReason)
   778  	}
   779  	return "updates to go.mod needed; to update it:\n\tgo mod tidy"
   780  }
   781  
   782  var errGoModDirty error = goModDirtyError{}
   783  
   784  // LoadWorkFile parses and checks the go.work file at the given path,
   785  // and returns the absolute paths of the workspace modules' modroots.
   786  // It does not modify the global state of the modload package.
   787  func LoadWorkFile(path string) (workFile *modfile.WorkFile, modRoots []string, err error) {
   788  	workDir := filepath.Dir(path)
   789  	wf, err := ReadWorkFile(path)
   790  	if err != nil {
   791  		return nil, nil, err
   792  	}
   793  	seen := map[string]bool{}
   794  	for _, d := range wf.Use {
   795  		modRoot := d.Path
   796  		if !filepath.IsAbs(modRoot) {
   797  			modRoot = filepath.Join(workDir, modRoot)
   798  		}
   799  
   800  		if seen[modRoot] {
   801  			return nil, nil, fmt.Errorf("error loading go.work:\n%s:%d: path %s appears multiple times in workspace", base.ShortPath(path), d.Syntax.Start.Line, modRoot)
   802  		}
   803  		seen[modRoot] = true
   804  		modRoots = append(modRoots, modRoot)
   805  	}
   806  
   807  	for _, g := range wf.Godebug {
   808  		if err := CheckGodebug("godebug", g.Key, g.Value); err != nil {
   809  			return nil, nil, fmt.Errorf("error loading go.work:\n%s:%d: %w", base.ShortPath(path), g.Syntax.Start.Line, err)
   810  		}
   811  	}
   812  
   813  	return wf, modRoots, nil
   814  }
   815  
   816  // ReadWorkFile reads and parses the go.work file at the given path.
   817  func ReadWorkFile(path string) (*modfile.WorkFile, error) {
   818  	path = base.ShortPath(path) // use short path in any errors
   819  	workData, err := fsys.ReadFile(path)
   820  	if err != nil {
   821  		return nil, fmt.Errorf("reading go.work: %w", err)
   822  	}
   823  
   824  	f, err := modfile.ParseWork(path, workData, nil)
   825  	if err != nil {
   826  		return nil, fmt.Errorf("errors parsing go.work:\n%w", err)
   827  	}
   828  	if f.Go != nil && gover.Compare(f.Go.Version, gover.Local()) > 0 && cfg.CmdName != "work edit" {
   829  		base.Fatal(&gover.TooNewError{What: base.ShortPath(path), GoVersion: f.Go.Version})
   830  	}
   831  	return f, nil
   832  }
   833  
   834  // WriteWorkFile cleans and writes out the go.work file to the given path.
   835  func WriteWorkFile(path string, wf *modfile.WorkFile) error {
   836  	wf.SortBlocks()
   837  	wf.Cleanup()
   838  	out := modfile.Format(wf.Syntax)
   839  
   840  	return os.WriteFile(path, out, 0666)
   841  }
   842  
   843  // UpdateWorkGoVersion updates the go line in wf to be at least goVers,
   844  // reporting whether it changed the file.
   845  func UpdateWorkGoVersion(wf *modfile.WorkFile, goVers string) (changed bool) {
   846  	old := gover.FromGoWork(wf)
   847  	if gover.Compare(old, goVers) >= 0 {
   848  		return false
   849  	}
   850  
   851  	wf.AddGoStmt(goVers)
   852  
   853  	if wf.Toolchain == nil {
   854  		return true
   855  	}
   856  
   857  	// Drop the toolchain line if it is implied by the go line,
   858  	// if its version is older than the version in the go line,
   859  	// or if it is asking for a toolchain older than Go 1.21,
   860  	// which will not understand the toolchain line.
   861  	// Previously, a toolchain line set to the local toolchain
   862  	// version was added so that future operations on the go file
   863  	// would use the same toolchain logic for reproducibility.
   864  	// This behavior seemed to cause user confusion without much
   865  	// benefit so it was removed. See #65847.
   866  	toolchain := wf.Toolchain.Name
   867  	toolVers := gover.FromToolchain(toolchain)
   868  	if toolchain == "go"+goVers || gover.Compare(toolVers, goVers) < 0 || gover.Compare(toolVers, gover.GoStrictVersion) < 0 {
   869  		wf.DropToolchainStmt()
   870  	}
   871  
   872  	return true
   873  }
   874  
   875  // UpdateWorkFile updates comments on directory directives in the go.work
   876  // file to include the associated module path.
   877  func UpdateWorkFile(wf *modfile.WorkFile) {
   878  	missingModulePaths := map[string]string{} // module directory listed in file -> abspath modroot
   879  
   880  	for _, d := range wf.Use {
   881  		if d.Path == "" {
   882  			continue // d is marked for deletion.
   883  		}
   884  		modRoot := d.Path
   885  		if d.ModulePath == "" {
   886  			missingModulePaths[d.Path] = modRoot
   887  		}
   888  	}
   889  
   890  	// Clean up and annotate directories.
   891  	// TODO(matloob): update x/mod to actually add module paths.
   892  	for moddir, absmodroot := range missingModulePaths {
   893  		_, f, err := ReadModFile(filepath.Join(absmodroot, "go.mod"), nil)
   894  		if err != nil {
   895  			continue // Error will be reported if modules are loaded.
   896  		}
   897  		wf.AddUse(moddir, f.Module.Mod.Path)
   898  	}
   899  }
   900  
   901  // LoadModFile sets Target and, if there is a main module, parses the initial
   902  // build list from its go.mod file.
   903  //
   904  // LoadModFile may make changes in memory, like adding a go directive and
   905  // ensuring requirements are consistent. The caller is responsible for ensuring
   906  // those changes are written to disk by calling LoadPackages or ListModules
   907  // (unless ExplicitWriteGoMod is set) or by calling WriteGoMod directly.
   908  //
   909  // As a side-effect, LoadModFile may change cfg.BuildMod to "vendor" if
   910  // -mod wasn't set explicitly and automatic vendoring should be enabled.
   911  //
   912  // If LoadModFile or CreateModFile has already been called, LoadModFile returns
   913  // the existing in-memory requirements (rather than re-reading them from disk).
   914  //
   915  // LoadModFile checks the roots of the module graph for consistency with each
   916  // other, but unlike LoadModGraph does not load the full module graph or check
   917  // it for global consistency. Most callers outside of the modload package should
   918  // use LoadModGraph instead.
   919  func LoadModFile(loaderstate *State, ctx context.Context) *Requirements {
   920  	rs, err := loadModFile(loaderstate, ctx, nil)
   921  	if err != nil {
   922  		base.Fatal(err)
   923  	}
   924  	return rs
   925  }
   926  
   927  func loadModFile(loaderstate *State, ctx context.Context, opts *PackageOpts) (*Requirements, error) {
   928  	if loaderstate.requirements != nil {
   929  		return loaderstate.requirements, nil
   930  	}
   931  
   932  	Init(loaderstate)
   933  	var workFile *modfile.WorkFile
   934  	if loaderstate.inWorkspaceMode() {
   935  		var err error
   936  		workFile, loaderstate.modRoots, err = LoadWorkFile(loaderstate.workFilePath)
   937  		if err != nil {
   938  			return nil, err
   939  		}
   940  		for _, modRoot := range loaderstate.modRoots {
   941  			sumFile := strings.TrimSuffix(modFilePath(modRoot), ".mod") + ".sum"
   942  			loaderstate.Fetcher().AddWorkspaceGoSumFile(sumFile)
   943  		}
   944  		loaderstate.Fetcher().SetGoSumFile(loaderstate.workFilePath + ".sum")
   945  	} else if len(loaderstate.modRoots) == 0 {
   946  		// We're in module mode, but not inside a module.
   947  		//
   948  		// Commands like 'go build', 'go run', 'go list' have no go.mod file to
   949  		// read or write. They would need to find and download the latest versions
   950  		// of a potentially large number of modules with no way to save version
   951  		// information. We can succeed slowly (but not reproducibly), but that's
   952  		// not usually a good experience.
   953  		//
   954  		// Instead, we forbid resolving import paths to modules other than std and
   955  		// cmd. Users may still build packages specified with .go files on the
   956  		// command line, but they'll see an error if those files import anything
   957  		// outside std.
   958  		//
   959  		// This can be overridden by calling AllowMissingModuleImports.
   960  		// For example, 'go get' does this, since it is expected to resolve paths.
   961  		//
   962  		// See golang.org/issue/32027.
   963  	} else {
   964  		loaderstate.Fetcher().SetGoSumFile(strings.TrimSuffix(modFilePath(loaderstate.modRoots[0]), ".mod") + ".sum")
   965  	}
   966  	if len(loaderstate.modRoots) == 0 {
   967  		// TODO(#49228): Instead of creating a fake module with an empty modroot,
   968  		// make MainModules.Len() == 0 mean that we're in module mode but not inside
   969  		// any module.
   970  		mainModule := module.Version{Path: "command-line-arguments"}
   971  		loaderstate.MainModules = makeMainModules(loaderstate, []module.Version{mainModule}, []string{""}, []*modfile.File{nil}, []*modFileIndex{nil}, nil)
   972  		var (
   973  			goVersion string
   974  			pruning   modPruning
   975  			roots     []module.Version
   976  			direct    = map[string]bool{"go": true}
   977  		)
   978  		if loaderstate.inWorkspaceMode() {
   979  			// Since we are in a workspace, the Go version for the synthetic
   980  			// "command-line-arguments" module must not exceed the Go version
   981  			// for the workspace.
   982  			goVersion = loaderstate.MainModules.GoVersion(loaderstate)
   983  			pruning = workspace
   984  			roots = []module.Version{
   985  				mainModule,
   986  				{Path: "go", Version: goVersion},
   987  				{Path: "toolchain", Version: gover.LocalToolchain()},
   988  			}
   989  		} else {
   990  			goVersion = gover.Local()
   991  			pruning = pruningForGoVersion(goVersion)
   992  			roots = []module.Version{
   993  				{Path: "go", Version: goVersion},
   994  				{Path: "toolchain", Version: gover.LocalToolchain()},
   995  			}
   996  		}
   997  		rawGoVersion.Store(mainModule, goVersion)
   998  		loaderstate.requirements = newRequirements(loaderstate, pruning, roots, direct)
   999  		if cfg.BuildMod == "vendor" {
  1000  			// For issue 56536: Some users may have GOFLAGS=-mod=vendor set.
  1001  			// Make sure it behaves as though the fake module is vendored
  1002  			// with no dependencies.
  1003  			loaderstate.requirements.initVendor(loaderstate, nil)
  1004  		}
  1005  		return loaderstate.requirements, nil
  1006  	}
  1007  
  1008  	var modFiles []*modfile.File
  1009  	var mainModules []module.Version
  1010  	var indices []*modFileIndex
  1011  	var errs []error
  1012  	for _, modroot := range loaderstate.modRoots {
  1013  		gomod := modFilePath(modroot)
  1014  		var fixed bool
  1015  		data, f, err := ReadModFile(gomod, fixVersion(loaderstate, ctx, &fixed))
  1016  		if err != nil {
  1017  			if loaderstate.inWorkspaceMode() {
  1018  				if tooNew, ok := err.(*gover.TooNewError); ok && !strings.HasPrefix(cfg.CmdName, "work ") {
  1019  					// Switching to a newer toolchain won't help - the go.work has the wrong version.
  1020  					// Report this more specific error, unless we are a command like 'go work use'
  1021  					// or 'go work sync', which will fix the problem after the caller sees the TooNewError
  1022  					// and switches to a newer toolchain.
  1023  					err = errWorkTooOld(gomod, workFile, tooNew.GoVersion)
  1024  				} else {
  1025  					err = fmt.Errorf("cannot load module %s listed in go.work file: %w",
  1026  						base.ShortPath(filepath.Dir(gomod)), base.ShortPathError(err))
  1027  				}
  1028  			}
  1029  			errs = append(errs, err)
  1030  			continue
  1031  		}
  1032  		if loaderstate.inWorkspaceMode() && !strings.HasPrefix(cfg.CmdName, "work ") {
  1033  			// Refuse to use workspace if its go version is too old.
  1034  			// Disable this check if we are a workspace command like work use or work sync,
  1035  			// which will fix the problem.
  1036  			mv := gover.FromGoMod(f)
  1037  			wv := gover.FromGoWork(workFile)
  1038  			if gover.Compare(mv, wv) > 0 && gover.Compare(mv, gover.GoStrictVersion) >= 0 {
  1039  				errs = append(errs, errWorkTooOld(gomod, workFile, mv))
  1040  				continue
  1041  			}
  1042  		}
  1043  
  1044  		if !loaderstate.inWorkspaceMode() {
  1045  			ok := true
  1046  			for _, g := range f.Godebug {
  1047  				if err := CheckGodebug("godebug", g.Key, g.Value); err != nil {
  1048  					errs = append(errs, fmt.Errorf("error loading go.mod:\n%s:%d: %v", base.ShortPath(gomod), g.Syntax.Start.Line, err))
  1049  					ok = false
  1050  				}
  1051  			}
  1052  			if !ok {
  1053  				continue
  1054  			}
  1055  		}
  1056  
  1057  		modFiles = append(modFiles, f)
  1058  		mainModule := f.Module.Mod
  1059  		mainModules = append(mainModules, mainModule)
  1060  		indices = append(indices, indexModFile(data, f, mainModule, fixed))
  1061  
  1062  		if err := module.CheckImportPath(f.Module.Mod.Path); err != nil {
  1063  			if pathErr, ok := err.(*module.InvalidPathError); ok {
  1064  				pathErr.Kind = "module"
  1065  			}
  1066  			errs = append(errs, err)
  1067  		}
  1068  	}
  1069  	if len(errs) > 0 {
  1070  		return nil, errors.Join(errs...)
  1071  	}
  1072  
  1073  	loaderstate.MainModules = makeMainModules(loaderstate, mainModules, loaderstate.modRoots, modFiles, indices, workFile)
  1074  	setDefaultBuildMod(loaderstate) // possibly enable automatic vendoring
  1075  	rs := requirementsFromModFiles(loaderstate, ctx, workFile, modFiles, opts)
  1076  
  1077  	if cfg.BuildMod == "vendor" {
  1078  		readVendorList(VendorDir(loaderstate))
  1079  		versions := loaderstate.MainModules.Versions()
  1080  		indexes := make([]*modFileIndex, 0, len(versions))
  1081  		modFiles := make([]*modfile.File, 0, len(versions))
  1082  		modRoots := make([]string, 0, len(versions))
  1083  		for _, m := range versions {
  1084  			indexes = append(indexes, loaderstate.MainModules.Index(m))
  1085  			modFiles = append(modFiles, loaderstate.MainModules.ModFile(m))
  1086  			modRoots = append(modRoots, loaderstate.MainModules.ModRoot(m))
  1087  		}
  1088  		checkVendorConsistency(loaderstate, indexes, modFiles, modRoots)
  1089  		rs.initVendor(loaderstate, vendorList)
  1090  	}
  1091  
  1092  	if loaderstate.inWorkspaceMode() {
  1093  		// We don't need to update the mod file so return early.
  1094  		loaderstate.requirements = rs
  1095  		return rs, nil
  1096  	}
  1097  
  1098  	mainModule := loaderstate.MainModules.mustGetSingleMainModule(loaderstate)
  1099  
  1100  	if rs.hasRedundantRoot(loaderstate) {
  1101  		// If any module path appears more than once in the roots, we know that the
  1102  		// go.mod file needs to be updated even though we have not yet loaded any
  1103  		// transitive dependencies.
  1104  		var err error
  1105  		rs, err = updateRoots(loaderstate, ctx, rs.direct, rs, nil, nil, false)
  1106  		if err != nil {
  1107  			return nil, err
  1108  		}
  1109  	}
  1110  
  1111  	if loaderstate.MainModules.Index(mainModule).goVersion == "" && rs.pruning != workspace {
  1112  		// TODO(#45551): Do something more principled instead of checking
  1113  		// cfg.CmdName directly here.
  1114  		if cfg.BuildMod == "mod" && cfg.CmdName != "mod graph" && cfg.CmdName != "mod why" {
  1115  			// go line is missing from go.mod; add one there and add to derived requirements.
  1116  			v := gover.Local()
  1117  			if opts != nil && opts.TidyGoVersion != "" {
  1118  				v = opts.TidyGoVersion
  1119  			}
  1120  			addGoStmt(loaderstate.MainModules.ModFile(mainModule), mainModule, v)
  1121  			rs = overrideRoots(loaderstate, ctx, rs, []module.Version{{Path: "go", Version: v}})
  1122  
  1123  			// We need to add a 'go' version to the go.mod file, but we must assume
  1124  			// that its existing contents match something between Go 1.11 and 1.16.
  1125  			// Go 1.11 through 1.16 do not support graph pruning, but the latest Go
  1126  			// version uses a pruned module graph — so we need to convert the
  1127  			// requirements to support pruning.
  1128  			if gover.Compare(v, gover.ExplicitIndirectVersion) >= 0 {
  1129  				var err error
  1130  				rs, err = convertPruning(loaderstate, ctx, rs, pruned)
  1131  				if err != nil {
  1132  					return nil, err
  1133  				}
  1134  			}
  1135  		} else {
  1136  			rawGoVersion.Store(mainModule, gover.DefaultGoModVersion)
  1137  		}
  1138  	}
  1139  
  1140  	loaderstate.requirements = rs
  1141  	return loaderstate.requirements, nil
  1142  }
  1143  
  1144  func errWorkTooOld(gomod string, wf *modfile.WorkFile, goVers string) error {
  1145  	verb := "lists"
  1146  	if wf == nil || wf.Go == nil {
  1147  		// A go.work file implicitly requires go1.18
  1148  		// even when it doesn't list any version.
  1149  		verb = "implicitly requires"
  1150  	}
  1151  	return fmt.Errorf("module %s listed in go.work file requires go >= %s, but go.work %s go %s; to update it:\n\tgo work use",
  1152  		base.ShortPath(filepath.Dir(gomod)), goVers, verb, gover.FromGoWork(wf))
  1153  }
  1154  
  1155  // CheckReservedModulePath checks whether the module path is a reserved module path
  1156  // that can't be used for a user's module.
  1157  func CheckReservedModulePath(path string) error {
  1158  	if gover.IsToolchain(path) {
  1159  		return errors.New("module path is reserved")
  1160  	}
  1161  
  1162  	return nil
  1163  }
  1164  
  1165  // CreateModFile initializes a new module by creating a go.mod file.
  1166  //
  1167  // If modPath is empty, CreateModFile will attempt to infer the path from the
  1168  // directory location within GOPATH.
  1169  //
  1170  // If a vendoring configuration file is present, CreateModFile will attempt to
  1171  // translate it to go.mod directives. The resulting build list may not be
  1172  // exactly the same as in the legacy configuration (for example, we can't get
  1173  // packages at multiple versions from the same module).
  1174  func CreateModFile(loaderstate *State, ctx context.Context, modPath string) {
  1175  	modRoot := base.Cwd()
  1176  	loaderstate.modRoots = []string{modRoot}
  1177  	Init(loaderstate)
  1178  	modFilePath := modFilePath(modRoot)
  1179  	if _, err := fsys.Stat(modFilePath); err == nil {
  1180  		base.Fatalf("go: %s already exists", modFilePath)
  1181  	}
  1182  
  1183  	if modPath == "" {
  1184  		var err error
  1185  		modPath, err = findModulePath(modRoot)
  1186  		if err != nil {
  1187  			base.Fatal(err)
  1188  		}
  1189  	} else if err := module.CheckImportPath(modPath); err != nil {
  1190  		if pathErr, ok := err.(*module.InvalidPathError); ok {
  1191  			pathErr.Kind = "module"
  1192  			// Same as build.IsLocalPath()
  1193  			if pathErr.Path == "." || pathErr.Path == ".." ||
  1194  				strings.HasPrefix(pathErr.Path, "./") || strings.HasPrefix(pathErr.Path, "../") {
  1195  				pathErr.Err = errors.New("is a local import path")
  1196  			}
  1197  		}
  1198  		base.Fatal(err)
  1199  	} else if err := CheckReservedModulePath(modPath); err != nil {
  1200  		base.Fatalf(`go: invalid module path %q: `, modPath)
  1201  	} else if _, _, ok := module.SplitPathVersion(modPath); !ok {
  1202  		if strings.HasPrefix(modPath, "gopkg.in/") {
  1203  			invalidMajorVersionMsg := fmt.Errorf("module paths beginning with gopkg.in/ must always have a major version suffix in the form of .vN:\n\tgo mod init %s", suggestGopkgIn(modPath))
  1204  			base.Fatalf(`go: invalid module path "%v": %v`, modPath, invalidMajorVersionMsg)
  1205  		}
  1206  		invalidMajorVersionMsg := fmt.Errorf("major version suffixes must be in the form of /vN and are only allowed for v2 or later:\n\tgo mod init %s", suggestModulePath(modPath))
  1207  		base.Fatalf(`go: invalid module path "%v": %v`, modPath, invalidMajorVersionMsg)
  1208  	}
  1209  
  1210  	fmt.Fprintf(os.Stderr, "go: creating new go.mod: module %s\n", modPath)
  1211  	modFile := new(modfile.File)
  1212  	modFile.AddModuleStmt(modPath)
  1213  	loaderstate.MainModules = makeMainModules(loaderstate, []module.Version{modFile.Module.Mod}, []string{modRoot}, []*modfile.File{modFile}, []*modFileIndex{nil}, nil)
  1214  	addGoStmt(modFile, modFile.Module.Mod, gover.Local()) // Add the go directive before converted module requirements.
  1215  
  1216  	rs := requirementsFromModFiles(loaderstate, ctx, nil, []*modfile.File{modFile}, nil)
  1217  	rs, err := updateRoots(loaderstate, ctx, rs.direct, rs, nil, nil, false)
  1218  	if err != nil {
  1219  		base.Fatal(err)
  1220  	}
  1221  	loaderstate.requirements = rs
  1222  	if err := commitRequirements(loaderstate, ctx, WriteOpts{}); err != nil {
  1223  		base.Fatal(err)
  1224  	}
  1225  
  1226  	// Suggest running 'go mod tidy' unless the project is empty. Even if we
  1227  	// imported all the correct requirements above, we're probably missing
  1228  	// some sums, so the next build command in -mod=readonly will likely fail.
  1229  	//
  1230  	// We look for non-hidden .go files or subdirectories to determine whether
  1231  	// this is an existing project. Walking the tree for packages would be more
  1232  	// accurate, but could take much longer.
  1233  	empty := true
  1234  	files, _ := os.ReadDir(modRoot)
  1235  	for _, f := range files {
  1236  		name := f.Name()
  1237  		if strings.HasPrefix(name, ".") || strings.HasPrefix(name, "_") {
  1238  			continue
  1239  		}
  1240  		if strings.HasSuffix(name, ".go") || f.IsDir() {
  1241  			empty = false
  1242  			break
  1243  		}
  1244  	}
  1245  	if !empty {
  1246  		fmt.Fprintf(os.Stderr, "go: to add module requirements and sums:\n\tgo mod tidy\n")
  1247  	}
  1248  }
  1249  
  1250  // fixVersion returns a modfile.VersionFixer implemented using the Query function.
  1251  //
  1252  // It resolves commit hashes and branch names to versions,
  1253  // canonicalizes versions that appeared in early vgo drafts,
  1254  // and does nothing for versions that already appear to be canonical.
  1255  //
  1256  // The VersionFixer sets 'fixed' if it ever returns a non-canonical version.
  1257  func fixVersion(loaderstate *State, ctx context.Context, fixed *bool) modfile.VersionFixer {
  1258  	return func(path, vers string) (resolved string, err error) {
  1259  		defer func() {
  1260  			if err == nil && resolved != vers {
  1261  				*fixed = true
  1262  			}
  1263  		}()
  1264  
  1265  		// Special case: remove the old -gopkgin- hack.
  1266  		if strings.HasPrefix(path, "gopkg.in/") && strings.Contains(vers, "-gopkgin-") {
  1267  			vers = vers[strings.Index(vers, "-gopkgin-")+len("-gopkgin-"):]
  1268  		}
  1269  
  1270  		// fixVersion is called speculatively on every
  1271  		// module, version pair from every go.mod file.
  1272  		// Avoid the query if it looks OK.
  1273  		_, pathMajor, ok := module.SplitPathVersion(path)
  1274  		if !ok {
  1275  			return "", &module.ModuleError{
  1276  				Path: path,
  1277  				Err: &module.InvalidVersionError{
  1278  					Version: vers,
  1279  					Err:     fmt.Errorf("malformed module path %q", path),
  1280  				},
  1281  			}
  1282  		}
  1283  		if vers != "" && module.CanonicalVersion(vers) == vers {
  1284  			if err := module.CheckPathMajor(vers, pathMajor); err != nil {
  1285  				return "", module.VersionError(module.Version{Path: path, Version: vers}, err)
  1286  			}
  1287  			return vers, nil
  1288  		}
  1289  
  1290  		info, err := Query(loaderstate, ctx, path, vers, "", nil)
  1291  		if err != nil {
  1292  			return "", err
  1293  		}
  1294  		return info.Version, nil
  1295  	}
  1296  }
  1297  
  1298  // AllowMissingModuleImports allows import paths to be resolved to modules
  1299  // when there is no module root. Normally, this is forbidden because it's slow
  1300  // and there's no way to make the result reproducible, but some commands
  1301  // like 'go get' are expected to do this.
  1302  //
  1303  // This function affects the default cfg.BuildMod when outside of a module,
  1304  // so it can only be called prior to Init.
  1305  func (s *State) AllowMissingModuleImports() {
  1306  	if s.initialized {
  1307  		panic("AllowMissingModuleImports after Init")
  1308  	}
  1309  	s.allowMissingModuleImports = true
  1310  }
  1311  
  1312  // makeMainModules creates a MainModuleSet and associated variables according to
  1313  // the given main modules.
  1314  func makeMainModules(loaderstate *State, ms []module.Version, rootDirs []string, modFiles []*modfile.File, indices []*modFileIndex, workFile *modfile.WorkFile) *MainModuleSet {
  1315  	for _, m := range ms {
  1316  		if m.Version != "" {
  1317  			panic("mainModulesCalled with module.Version with non empty Version field: " + fmt.Sprintf("%#v", m))
  1318  		}
  1319  	}
  1320  	modRootContainingCWD := findModuleRoot(base.Cwd())
  1321  	mainModules := &MainModuleSet{
  1322  		versions:        slices.Clip(ms),
  1323  		inGorootSrc:     map[module.Version]bool{},
  1324  		pathPrefix:      map[module.Version]string{},
  1325  		modRoot:         map[module.Version]string{},
  1326  		modFiles:        map[module.Version]*modfile.File{},
  1327  		indices:         map[module.Version]*modFileIndex{},
  1328  		highestReplaced: map[string]string{},
  1329  		tools:           map[string]bool{},
  1330  		workFile:        workFile,
  1331  	}
  1332  	var workFileReplaces []*modfile.Replace
  1333  	if workFile != nil {
  1334  		workFileReplaces = workFile.Replace
  1335  		mainModules.workFileReplaceMap = toReplaceMap(workFile.Replace)
  1336  	}
  1337  	mainModulePaths := make(map[string]bool)
  1338  	for _, m := range ms {
  1339  		if mainModulePaths[m.Path] {
  1340  			base.Errorf("go: module %s appears multiple times in workspace", m.Path)
  1341  		}
  1342  		mainModulePaths[m.Path] = true
  1343  	}
  1344  	replacedByWorkFile := make(map[string]bool)
  1345  	replacements := make(map[module.Version]module.Version)
  1346  	for _, r := range workFileReplaces {
  1347  		if mainModulePaths[r.Old.Path] && r.Old.Version == "" {
  1348  			base.Errorf("go: workspace module %v is replaced at all versions in the go.work file. To fix, remove the replacement from the go.work file or specify the version at which to replace the module.", r.Old.Path)
  1349  		}
  1350  		replacedByWorkFile[r.Old.Path] = true
  1351  		v, ok := mainModules.highestReplaced[r.Old.Path]
  1352  		if !ok || gover.ModCompare(r.Old.Path, r.Old.Version, v) > 0 {
  1353  			mainModules.highestReplaced[r.Old.Path] = r.Old.Version
  1354  		}
  1355  		replacements[r.Old] = r.New
  1356  	}
  1357  	for i, m := range ms {
  1358  		mainModules.pathPrefix[m] = m.Path
  1359  		mainModules.modRoot[m] = rootDirs[i]
  1360  		mainModules.modFiles[m] = modFiles[i]
  1361  		mainModules.indices[m] = indices[i]
  1362  
  1363  		if mainModules.modRoot[m] == modRootContainingCWD {
  1364  			mainModules.modContainingCWD = m
  1365  		}
  1366  
  1367  		if rel := search.InDir(rootDirs[i], cfg.GOROOTsrc); rel != "" {
  1368  			mainModules.inGorootSrc[m] = true
  1369  			if m.Path == "std" {
  1370  				// The "std" module in GOROOT/src is the Go standard library. Unlike other
  1371  				// modules, the packages in the "std" module have no import-path prefix.
  1372  				//
  1373  				// Modules named "std" outside of GOROOT/src do not receive this special
  1374  				// treatment, so it is possible to run 'go test .' in other GOROOTs to
  1375  				// test individual packages using a combination of the modified package
  1376  				// and the ordinary standard library.
  1377  				// (See https://golang.org/issue/30756.)
  1378  				mainModules.pathPrefix[m] = ""
  1379  			}
  1380  		}
  1381  
  1382  		if modFiles[i] != nil {
  1383  			curModuleReplaces := make(map[module.Version]bool)
  1384  			for _, r := range modFiles[i].Replace {
  1385  				if replacedByWorkFile[r.Old.Path] {
  1386  					continue
  1387  				}
  1388  				var newV module.Version = r.New
  1389  				if WorkFilePath(loaderstate) != "" && newV.Version == "" && !filepath.IsAbs(newV.Path) {
  1390  					// Since we are in a workspace, we may be loading replacements from
  1391  					// multiple go.mod files. Relative paths in those replacement are
  1392  					// relative to the go.mod file, not the workspace, so the same string
  1393  					// may refer to two different paths and different strings may refer to
  1394  					// the same path. Convert them all to be absolute instead.
  1395  					//
  1396  					// (We could do this outside of a workspace too, but it would mean that
  1397  					// replacement paths in error strings needlessly differ from what's in
  1398  					// the go.mod file.)
  1399  					newV.Path = filepath.Join(rootDirs[i], newV.Path)
  1400  				}
  1401  				if prev, ok := replacements[r.Old]; ok && !curModuleReplaces[r.Old] && prev != newV {
  1402  					base.Fatalf("go: conflicting replacements for %v:\n\t%v\n\t%v\nuse \"go work edit -replace %v=[override]\" to resolve", r.Old, prev, newV, r.Old)
  1403  				}
  1404  				curModuleReplaces[r.Old] = true
  1405  				replacements[r.Old] = newV
  1406  
  1407  				v, ok := mainModules.highestReplaced[r.Old.Path]
  1408  				if !ok || gover.ModCompare(r.Old.Path, r.Old.Version, v) > 0 {
  1409  					mainModules.highestReplaced[r.Old.Path] = r.Old.Version
  1410  				}
  1411  			}
  1412  
  1413  			for _, t := range modFiles[i].Tool {
  1414  				if err := module.CheckImportPath(t.Path); err != nil {
  1415  					if e, ok := err.(*module.InvalidPathError); ok {
  1416  						e.Kind = "tool"
  1417  					}
  1418  					base.Fatal(err)
  1419  				}
  1420  
  1421  				mainModules.tools[t.Path] = true
  1422  			}
  1423  		}
  1424  	}
  1425  
  1426  	return mainModules
  1427  }
  1428  
  1429  // requirementsFromModFiles returns the set of non-excluded requirements from
  1430  // the global modFile.
  1431  func requirementsFromModFiles(loaderstate *State, ctx context.Context, workFile *modfile.WorkFile, modFiles []*modfile.File, opts *PackageOpts) *Requirements {
  1432  	var roots []module.Version
  1433  	direct := map[string]bool{}
  1434  	var pruning modPruning
  1435  	if loaderstate.inWorkspaceMode() {
  1436  		pruning = workspace
  1437  		roots = make([]module.Version, len(loaderstate.MainModules.Versions()), 2+len(loaderstate.MainModules.Versions()))
  1438  		copy(roots, loaderstate.MainModules.Versions())
  1439  		goVersion := gover.FromGoWork(workFile)
  1440  		var toolchain string
  1441  		if workFile.Toolchain != nil {
  1442  			toolchain = workFile.Toolchain.Name
  1443  		}
  1444  		roots = appendGoAndToolchainRoots(roots, goVersion, toolchain, direct)
  1445  		direct = directRequirements(modFiles)
  1446  	} else {
  1447  		pruning = pruningForGoVersion(loaderstate.MainModules.GoVersion(loaderstate))
  1448  		if len(modFiles) != 1 {
  1449  			panic(fmt.Errorf("requirementsFromModFiles called with %v modfiles outside workspace mode", len(modFiles)))
  1450  		}
  1451  		modFile := modFiles[0]
  1452  		roots, direct = rootsFromModFile(loaderstate, loaderstate.MainModules.mustGetSingleMainModule(loaderstate), modFile, withToolchainRoot)
  1453  	}
  1454  
  1455  	gover.ModSort(roots)
  1456  	rs := newRequirements(loaderstate, pruning, roots, direct)
  1457  	return rs
  1458  }
  1459  
  1460  type addToolchainRoot bool
  1461  
  1462  const (
  1463  	omitToolchainRoot addToolchainRoot = false
  1464  	withToolchainRoot                  = true
  1465  )
  1466  
  1467  func directRequirements(modFiles []*modfile.File) map[string]bool {
  1468  	direct := make(map[string]bool)
  1469  	for _, modFile := range modFiles {
  1470  		for _, r := range modFile.Require {
  1471  			if !r.Indirect {
  1472  				direct[r.Mod.Path] = true
  1473  			}
  1474  		}
  1475  	}
  1476  	return direct
  1477  }
  1478  
  1479  func rootsFromModFile(loaderstate *State, m module.Version, modFile *modfile.File, addToolchainRoot addToolchainRoot) (roots []module.Version, direct map[string]bool) {
  1480  	direct = make(map[string]bool)
  1481  	padding := 2 // Add padding for the toolchain and go version, added upon return.
  1482  	if !addToolchainRoot {
  1483  		padding = 1
  1484  	}
  1485  	roots = make([]module.Version, 0, padding+len(modFile.Require))
  1486  	for _, r := range modFile.Require {
  1487  		if index := loaderstate.MainModules.Index(m); index != nil && index.exclude[r.Mod] {
  1488  			if cfg.BuildMod == "mod" {
  1489  				fmt.Fprintf(os.Stderr, "go: dropping requirement on excluded version %s %s\n", r.Mod.Path, r.Mod.Version)
  1490  			} else {
  1491  				fmt.Fprintf(os.Stderr, "go: ignoring requirement on excluded version %s %s\n", r.Mod.Path, r.Mod.Version)
  1492  			}
  1493  			continue
  1494  		}
  1495  
  1496  		roots = append(roots, r.Mod)
  1497  		if !r.Indirect {
  1498  			direct[r.Mod.Path] = true
  1499  		}
  1500  	}
  1501  	goVersion := gover.FromGoMod(modFile)
  1502  	var toolchain string
  1503  	if addToolchainRoot && modFile.Toolchain != nil {
  1504  		toolchain = modFile.Toolchain.Name
  1505  	}
  1506  	roots = appendGoAndToolchainRoots(roots, goVersion, toolchain, direct)
  1507  	return roots, direct
  1508  }
  1509  
  1510  func appendGoAndToolchainRoots(roots []module.Version, goVersion, toolchain string, direct map[string]bool) []module.Version {
  1511  	// Add explicit go and toolchain versions, inferring as needed.
  1512  	roots = append(roots, module.Version{Path: "go", Version: goVersion})
  1513  	direct["go"] = true // Every module directly uses the language and runtime.
  1514  
  1515  	if toolchain != "" {
  1516  		roots = append(roots, module.Version{Path: "toolchain", Version: toolchain})
  1517  		// Leave the toolchain as indirect: nothing in the user's module directly
  1518  		// imports a package from the toolchain, and (like an indirect dependency in
  1519  		// a module without graph pruning) we may remove the toolchain line
  1520  		// automatically if the 'go' version is changed so that it implies the exact
  1521  		// same toolchain.
  1522  	}
  1523  	return roots
  1524  }
  1525  
  1526  // setDefaultBuildMod sets a default value for cfg.BuildMod if the -mod flag
  1527  // wasn't provided. setDefaultBuildMod may be called multiple times.
  1528  func setDefaultBuildMod(loaderstate *State) {
  1529  	if cfg.BuildModExplicit {
  1530  		if loaderstate.inWorkspaceMode() && cfg.BuildMod != "readonly" && cfg.BuildMod != "vendor" {
  1531  			switch cfg.CmdName {
  1532  			case "work sync", "mod graph", "mod verify", "mod why":
  1533  				// These commands run with BuildMod set to mod, but they don't take the
  1534  				// -mod flag, so we should never get here.
  1535  				panic("in workspace mode and -mod was set explicitly, but command doesn't support setting -mod")
  1536  			default:
  1537  				base.Fatalf("go: -mod may only be set to readonly or vendor when in workspace mode, but it is set to %q"+
  1538  					"\n\tRemove the -mod flag to use the default readonly value, "+
  1539  					"\n\tor set GOWORK=off to disable workspace mode.", cfg.BuildMod)
  1540  			}
  1541  		}
  1542  		// Don't override an explicit '-mod=' argument.
  1543  		return
  1544  	}
  1545  
  1546  	// TODO(#40775): commands should pass in the module mode as an option
  1547  	// to modload functions instead of relying on an implicit setting
  1548  	// based on command name.
  1549  	switch cfg.CmdName {
  1550  	case "get", "mod download", "mod init", "mod tidy", "work sync":
  1551  		// These commands are intended to update go.mod and go.sum.
  1552  		cfg.BuildMod = "mod"
  1553  		return
  1554  	case "mod graph", "mod verify", "mod why":
  1555  		// These commands should not update go.mod or go.sum, but they should be
  1556  		// able to fetch modules not in go.sum and should not report errors if
  1557  		// go.mod is inconsistent. They're useful for debugging, and they need
  1558  		// to work in buggy situations.
  1559  		cfg.BuildMod = "mod"
  1560  		return
  1561  	case "mod vendor", "work vendor":
  1562  		cfg.BuildMod = "readonly"
  1563  		return
  1564  	}
  1565  	if loaderstate.modRoots == nil {
  1566  		if loaderstate.allowMissingModuleImports {
  1567  			cfg.BuildMod = "mod"
  1568  		} else {
  1569  			cfg.BuildMod = "readonly"
  1570  		}
  1571  		return
  1572  	}
  1573  
  1574  	if len(loaderstate.modRoots) >= 1 {
  1575  		var goVersion string
  1576  		var versionSource string
  1577  		if loaderstate.inWorkspaceMode() {
  1578  			versionSource = "go.work"
  1579  			if wfg := loaderstate.MainModules.WorkFile().Go; wfg != nil {
  1580  				goVersion = wfg.Version
  1581  			}
  1582  		} else {
  1583  			versionSource = "go.mod"
  1584  			index := loaderstate.MainModules.GetSingleIndexOrNil(loaderstate)
  1585  			if index != nil {
  1586  				goVersion = index.goVersion
  1587  			}
  1588  		}
  1589  		vendorDir := ""
  1590  		if loaderstate.workFilePath != "" {
  1591  			vendorDir = filepath.Join(filepath.Dir(loaderstate.workFilePath), "vendor")
  1592  		} else {
  1593  			if len(loaderstate.modRoots) != 1 {
  1594  				panic(fmt.Errorf("outside workspace mode, but have %v modRoots", loaderstate.modRoots))
  1595  			}
  1596  			vendorDir = filepath.Join(loaderstate.modRoots[0], "vendor")
  1597  		}
  1598  		if fi, err := fsys.Stat(vendorDir); err == nil && fi.IsDir() {
  1599  			if goVersion != "" {
  1600  				if gover.Compare(goVersion, "1.14") < 0 {
  1601  					// The go version is less than 1.14. Don't set -mod=vendor by default.
  1602  					// Since a vendor directory exists, we should record why we didn't use it.
  1603  					// This message won't normally be shown, but it may appear with import errors.
  1604  					cfg.BuildModReason = fmt.Sprintf("Go version in "+versionSource+" is %s, so vendor directory was not used.", goVersion)
  1605  				} else {
  1606  					vendoredWorkspace, err := modulesTextIsForWorkspace(vendorDir)
  1607  					if err != nil {
  1608  						base.Fatalf("go: reading modules.txt for vendor directory: %v", err)
  1609  					}
  1610  					if vendoredWorkspace != (versionSource == "go.work") {
  1611  						if vendoredWorkspace {
  1612  							cfg.BuildModReason = "Outside workspace mode, but vendor directory is for a workspace."
  1613  						} else {
  1614  							cfg.BuildModReason = "In workspace mode, but vendor directory is not for a workspace"
  1615  						}
  1616  					} else {
  1617  						// The Go version is at least 1.14, a vendor directory exists, and
  1618  						// the modules.txt was generated in the same mode the command is running in.
  1619  						// Set -mod=vendor by default.
  1620  						cfg.BuildMod = "vendor"
  1621  						cfg.BuildModReason = "Go version in " + versionSource + " is at least 1.14 and vendor directory exists."
  1622  						return
  1623  					}
  1624  				}
  1625  			} else {
  1626  				cfg.BuildModReason = fmt.Sprintf("Go version in %s is unspecified, so vendor directory was not used.", versionSource)
  1627  			}
  1628  		}
  1629  	}
  1630  
  1631  	cfg.BuildMod = "readonly"
  1632  }
  1633  
  1634  func modulesTextIsForWorkspace(vendorDir string) (bool, error) {
  1635  	f, err := fsys.Open(filepath.Join(vendorDir, "modules.txt"))
  1636  	if errors.Is(err, os.ErrNotExist) {
  1637  		// Some vendor directories exist that don't contain modules.txt.
  1638  		// This mostly happens when converting to modules.
  1639  		// We want to preserve the behavior that mod=vendor is set (even though
  1640  		// readVendorList does nothing in that case).
  1641  		return false, nil
  1642  	}
  1643  	if err != nil {
  1644  		return false, err
  1645  	}
  1646  	defer f.Close()
  1647  	var buf [512]byte
  1648  	n, err := f.Read(buf[:])
  1649  	if err != nil && err != io.EOF {
  1650  		return false, err
  1651  	}
  1652  	line, _, _ := strings.Cut(string(buf[:n]), "\n")
  1653  	if annotations, ok := strings.CutPrefix(line, "## "); ok {
  1654  		for entry := range strings.SplitSeq(annotations, ";") {
  1655  			entry = strings.TrimSpace(entry)
  1656  			if entry == "workspace" {
  1657  				return true, nil
  1658  			}
  1659  		}
  1660  	}
  1661  	return false, nil
  1662  }
  1663  
  1664  func mustHaveCompleteRequirements(loaderstate *State) bool {
  1665  	return cfg.BuildMod != "mod" && !loaderstate.inWorkspaceMode()
  1666  }
  1667  
  1668  // addGoStmt adds a go directive to the go.mod file if it does not already
  1669  // include one. The 'go' version added, if any, is the latest version supported
  1670  // by this toolchain.
  1671  func addGoStmt(modFile *modfile.File, mod module.Version, v string) {
  1672  	if modFile.Go != nil && modFile.Go.Version != "" {
  1673  		return
  1674  	}
  1675  	forceGoStmt(modFile, mod, v)
  1676  }
  1677  
  1678  func forceGoStmt(modFile *modfile.File, mod module.Version, v string) {
  1679  	if err := modFile.AddGoStmt(v); err != nil {
  1680  		base.Fatalf("go: internal error: %v", err)
  1681  	}
  1682  	rawGoVersion.Store(mod, v)
  1683  }
  1684  
  1685  var altConfigs = []string{
  1686  	".git/config",
  1687  }
  1688  
  1689  func findModuleRoot(dir string) (roots string) {
  1690  	if dir == "" {
  1691  		panic("dir not set")
  1692  	}
  1693  	dir = filepath.Clean(dir)
  1694  
  1695  	// Look for enclosing go.mod.
  1696  	for {
  1697  		if fi, err := fsys.Stat(filepath.Join(dir, "go.mod")); err == nil && !fi.IsDir() {
  1698  			return dir
  1699  		}
  1700  		d := filepath.Dir(dir)
  1701  		if d == dir {
  1702  			break
  1703  		}
  1704  		dir = d
  1705  	}
  1706  	return ""
  1707  }
  1708  
  1709  func findWorkspaceFile(dir string) (root string) {
  1710  	if dir == "" {
  1711  		panic("dir not set")
  1712  	}
  1713  	dir = filepath.Clean(dir)
  1714  
  1715  	// Look for enclosing go.mod.
  1716  	for {
  1717  		f := filepath.Join(dir, "go.work")
  1718  		if fi, err := fsys.Stat(f); err == nil && !fi.IsDir() {
  1719  			return f
  1720  		}
  1721  		d := filepath.Dir(dir)
  1722  		if d == dir {
  1723  			break
  1724  		}
  1725  		if d == cfg.GOROOT {
  1726  			// As a special case, don't cross GOROOT to find a go.work file.
  1727  			// The standard library and commands built in go always use the vendored
  1728  			// dependencies, so avoid using a most likely irrelevant go.work file.
  1729  			return ""
  1730  		}
  1731  		dir = d
  1732  	}
  1733  	return ""
  1734  }
  1735  
  1736  func findAltConfig(dir string) (root, name string) {
  1737  	if dir == "" {
  1738  		panic("dir not set")
  1739  	}
  1740  	dir = filepath.Clean(dir)
  1741  	if rel := search.InDir(dir, cfg.BuildContext.GOROOT); rel != "" {
  1742  		// Don't suggest creating a module from $GOROOT/.git/config
  1743  		// or a config file found in any parent of $GOROOT (see #34191).
  1744  		return "", ""
  1745  	}
  1746  	for {
  1747  		for _, name := range altConfigs {
  1748  			if fi, err := fsys.Stat(filepath.Join(dir, name)); err == nil && !fi.IsDir() {
  1749  				return dir, name
  1750  			}
  1751  		}
  1752  		d := filepath.Dir(dir)
  1753  		if d == dir {
  1754  			break
  1755  		}
  1756  		dir = d
  1757  	}
  1758  	return "", ""
  1759  }
  1760  
  1761  func findModulePath(dir string) (string, error) {
  1762  	// TODO(bcmills): once we have located a plausible module path, we should
  1763  	// query version control (if available) to verify that it matches the major
  1764  	// version of the most recent tag.
  1765  	// See https://golang.org/issue/29433, https://golang.org/issue/27009, and
  1766  	// https://golang.org/issue/31549.
  1767  
  1768  	// Cast about for import comments,
  1769  	// first in top-level directory, then in subdirectories.
  1770  	list, _ := os.ReadDir(dir)
  1771  	for _, info := range list {
  1772  		if info.Type().IsRegular() && strings.HasSuffix(info.Name(), ".go") {
  1773  			if com := findImportComment(filepath.Join(dir, info.Name())); com != "" {
  1774  				return com, nil
  1775  			}
  1776  		}
  1777  	}
  1778  	for _, info1 := range list {
  1779  		if info1.IsDir() {
  1780  			files, _ := os.ReadDir(filepath.Join(dir, info1.Name()))
  1781  			for _, info2 := range files {
  1782  				if info2.Type().IsRegular() && strings.HasSuffix(info2.Name(), ".go") {
  1783  					if com := findImportComment(filepath.Join(dir, info1.Name(), info2.Name())); com != "" {
  1784  						return path.Dir(com), nil
  1785  					}
  1786  				}
  1787  			}
  1788  		}
  1789  	}
  1790  
  1791  	// Look for path in GOPATH.
  1792  	var badPathErr error
  1793  	for _, gpdir := range filepath.SplitList(cfg.BuildContext.GOPATH) {
  1794  		if gpdir == "" {
  1795  			continue
  1796  		}
  1797  		if rel := search.InDir(dir, filepath.Join(gpdir, "src")); rel != "" && rel != "." {
  1798  			path := filepath.ToSlash(rel)
  1799  			// gorelease will alert users publishing their modules to fix their paths.
  1800  			if err := module.CheckImportPath(path); err != nil {
  1801  				badPathErr = err
  1802  				break
  1803  			}
  1804  			return path, nil
  1805  		}
  1806  	}
  1807  
  1808  	reason := "outside GOPATH, module path must be specified"
  1809  	if badPathErr != nil {
  1810  		// return a different error message if the module was in GOPATH, but
  1811  		// the module path determined above would be an invalid path.
  1812  		reason = fmt.Sprintf("bad module path inferred from directory in GOPATH: %v", badPathErr)
  1813  	}
  1814  	msg := `cannot determine module path for source directory %s (%s)
  1815  
  1816  Example usage:
  1817  	'go mod init example.com/m' to initialize a v0 or v1 module
  1818  	'go mod init example.com/m/v2' to initialize a v2 module
  1819  
  1820  Run 'go help mod init' for more information.
  1821  `
  1822  	return "", fmt.Errorf(msg, dir, reason)
  1823  }
  1824  
  1825  var (
  1826  	importCommentRE = lazyregexp.New(`(?m)^package[ \t]+[^ \t\r\n/]+[ \t]+//[ \t]+import[ \t]+(\"[^"]+\")[ \t]*\r?\n`)
  1827  )
  1828  
  1829  func findImportComment(file string) string {
  1830  	data, err := os.ReadFile(file)
  1831  	if err != nil {
  1832  		return ""
  1833  	}
  1834  	m := importCommentRE.FindSubmatch(data)
  1835  	if m == nil {
  1836  		return ""
  1837  	}
  1838  	path, err := strconv.Unquote(string(m[1]))
  1839  	if err != nil {
  1840  		return ""
  1841  	}
  1842  	return path
  1843  }
  1844  
  1845  // WriteOpts control the behavior of WriteGoMod.
  1846  type WriteOpts struct {
  1847  	DropToolchain     bool // go get toolchain@none
  1848  	ExplicitToolchain bool // go get has set explicit toolchain version
  1849  
  1850  	AddTools  []string // go get -tool example.com/m1
  1851  	DropTools []string // go get -tool example.com/m1@none
  1852  
  1853  	// TODO(bcmills): Make 'go mod tidy' update the go version in the Requirements
  1854  	// instead of writing directly to the modfile.File
  1855  	TidyWroteGo bool // Go.Version field already updated by 'go mod tidy'
  1856  }
  1857  
  1858  // WriteGoMod writes the current build list back to go.mod.
  1859  func WriteGoMod(loaderstate *State, ctx context.Context, opts WriteOpts) error {
  1860  	loaderstate.requirements = LoadModFile(loaderstate, ctx)
  1861  	return commitRequirements(loaderstate, ctx, opts)
  1862  }
  1863  
  1864  var errNoChange = errors.New("no update needed")
  1865  
  1866  // UpdateGoModFromReqs returns a modified go.mod file using the current
  1867  // requirements. It does not commit these changes to disk.
  1868  func UpdateGoModFromReqs(loaderstate *State, ctx context.Context, opts WriteOpts) (before, after []byte, modFile *modfile.File, err error) {
  1869  	if loaderstate.MainModules.Len() != 1 || loaderstate.MainModules.ModRoot(loaderstate.MainModules.Versions()[0]) == "" {
  1870  		// We aren't in a module, so we don't have anywhere to write a go.mod file.
  1871  		return nil, nil, nil, errNoChange
  1872  	}
  1873  	mainModule := loaderstate.MainModules.mustGetSingleMainModule(loaderstate)
  1874  	modFile = loaderstate.MainModules.ModFile(mainModule)
  1875  	if modFile == nil {
  1876  		// command-line-arguments has no .mod file to write.
  1877  		return nil, nil, nil, errNoChange
  1878  	}
  1879  	before, err = modFile.Format()
  1880  	if err != nil {
  1881  		return nil, nil, nil, err
  1882  	}
  1883  
  1884  	var list []*modfile.Require
  1885  	toolchain := ""
  1886  	goVersion := ""
  1887  	for _, m := range loaderstate.requirements.rootModules {
  1888  		if m.Path == "go" {
  1889  			goVersion = m.Version
  1890  			continue
  1891  		}
  1892  		if m.Path == "toolchain" {
  1893  			toolchain = m.Version
  1894  			continue
  1895  		}
  1896  		list = append(list, &modfile.Require{
  1897  			Mod:      m,
  1898  			Indirect: !loaderstate.requirements.direct[m.Path],
  1899  		})
  1900  	}
  1901  
  1902  	// Update go line.
  1903  	// Every MVS graph we consider should have go as a root,
  1904  	// and toolchain is either implied by the go line or explicitly a root.
  1905  	if goVersion == "" {
  1906  		base.Fatalf("go: internal error: missing go root module in WriteGoMod")
  1907  	}
  1908  	if gover.Compare(goVersion, gover.Local()) > 0 {
  1909  		// We cannot assume that we know how to update a go.mod to a newer version.
  1910  		return nil, nil, nil, &gover.TooNewError{What: "updating go.mod", GoVersion: goVersion}
  1911  	}
  1912  	wroteGo := opts.TidyWroteGo
  1913  	if !wroteGo && modFile.Go == nil || modFile.Go.Version != goVersion {
  1914  		alwaysUpdate := cfg.BuildMod == "mod" || cfg.CmdName == "mod tidy" || cfg.CmdName == "get"
  1915  		if modFile.Go == nil && goVersion == gover.DefaultGoModVersion && !alwaysUpdate {
  1916  			// The go.mod has no go line, the implied default Go version matches
  1917  			// what we've computed for the graph, and we're not in one of the
  1918  			// traditional go.mod-updating programs, so leave it alone.
  1919  		} else {
  1920  			wroteGo = true
  1921  			forceGoStmt(modFile, mainModule, goVersion)
  1922  		}
  1923  	}
  1924  	if toolchain == "" {
  1925  		toolchain = "go" + goVersion
  1926  	}
  1927  
  1928  	toolVers := gover.FromToolchain(toolchain)
  1929  	if opts.DropToolchain || toolchain == "go"+goVersion || (gover.Compare(toolVers, gover.GoStrictVersion) < 0 && !opts.ExplicitToolchain) {
  1930  		// go get toolchain@none or toolchain matches go line or isn't valid; drop it.
  1931  		// TODO(#57001): 'go get' should reject explicit toolchains below GoStrictVersion.
  1932  		modFile.DropToolchainStmt()
  1933  	} else {
  1934  		modFile.AddToolchainStmt(toolchain)
  1935  	}
  1936  
  1937  	for _, path := range opts.AddTools {
  1938  		modFile.AddTool(path)
  1939  	}
  1940  
  1941  	for _, path := range opts.DropTools {
  1942  		modFile.DropTool(path)
  1943  	}
  1944  
  1945  	// Update require blocks.
  1946  	if gover.Compare(goVersion, gover.SeparateIndirectVersion) < 0 {
  1947  		modFile.SetRequire(list)
  1948  	} else {
  1949  		modFile.SetRequireSeparateIndirect(list)
  1950  	}
  1951  	modFile.Cleanup()
  1952  	after, err = modFile.Format()
  1953  	if err != nil {
  1954  		return nil, nil, nil, err
  1955  	}
  1956  	return before, after, modFile, nil
  1957  }
  1958  
  1959  // commitRequirements ensures go.mod and go.sum are up to date with the current
  1960  // requirements.
  1961  //
  1962  // In "mod" mode, commitRequirements writes changes to go.mod and go.sum.
  1963  //
  1964  // In "readonly" and "vendor" modes, commitRequirements returns an error if
  1965  // go.mod or go.sum are out of date in a semantically significant way.
  1966  //
  1967  // In workspace mode, commitRequirements only writes changes to go.work.sum.
  1968  func commitRequirements(loaderstate *State, ctx context.Context, opts WriteOpts) (err error) {
  1969  	if loaderstate.inWorkspaceMode() {
  1970  		// go.mod files aren't updated in workspace mode, but we still want to
  1971  		// update the go.work.sum file.
  1972  		return loaderstate.Fetcher().WriteGoSum(ctx, keepSums(loaderstate, ctx, loaded, loaderstate.requirements, addBuildListZipSums), mustHaveCompleteRequirements(loaderstate))
  1973  	}
  1974  	_, updatedGoMod, modFile, err := UpdateGoModFromReqs(loaderstate, ctx, opts)
  1975  	if err != nil {
  1976  		if errors.Is(err, errNoChange) {
  1977  			return nil
  1978  		}
  1979  		return err
  1980  	}
  1981  
  1982  	index := loaderstate.MainModules.GetSingleIndexOrNil(loaderstate)
  1983  	dirty := index.modFileIsDirty(modFile) || len(opts.DropTools) > 0 || len(opts.AddTools) > 0
  1984  	if dirty && cfg.BuildMod != "mod" {
  1985  		// If we're about to fail due to -mod=readonly,
  1986  		// prefer to report a dirty go.mod over a dirty go.sum
  1987  		return errGoModDirty
  1988  	}
  1989  
  1990  	if !dirty && cfg.CmdName != "mod tidy" {
  1991  		// The go.mod file has the same semantic content that it had before
  1992  		// (but not necessarily the same exact bytes).
  1993  		// Don't write go.mod, but write go.sum in case we added or trimmed sums.
  1994  		// 'go mod init' shouldn't write go.sum, since it will be incomplete.
  1995  		if cfg.CmdName != "mod init" {
  1996  			if err := loaderstate.Fetcher().WriteGoSum(ctx, keepSums(loaderstate, ctx, loaded, loaderstate.requirements, addBuildListZipSums), mustHaveCompleteRequirements(loaderstate)); err != nil {
  1997  				return err
  1998  			}
  1999  		}
  2000  		return nil
  2001  	}
  2002  
  2003  	mainModule := loaderstate.MainModules.mustGetSingleMainModule(loaderstate)
  2004  	modFilePath := modFilePath(loaderstate.MainModules.ModRoot(mainModule))
  2005  	if fsys.Replaced(modFilePath) {
  2006  		if dirty {
  2007  			return errors.New("updates to go.mod needed, but go.mod is part of the overlay specified with -overlay")
  2008  		}
  2009  		return nil
  2010  	}
  2011  	defer func() {
  2012  		// At this point we have determined to make the go.mod file on disk equal to new.
  2013  		loaderstate.MainModules.SetIndex(mainModule, indexModFile(updatedGoMod, modFile, mainModule, false))
  2014  
  2015  		// Update go.sum after releasing the side lock and refreshing the index.
  2016  		// 'go mod init' shouldn't write go.sum, since it will be incomplete.
  2017  		if cfg.CmdName != "mod init" {
  2018  			if err == nil {
  2019  				err = loaderstate.Fetcher().WriteGoSum(ctx, keepSums(loaderstate, ctx, loaded, loaderstate.requirements, addBuildListZipSums), mustHaveCompleteRequirements(loaderstate))
  2020  			}
  2021  		}
  2022  	}()
  2023  
  2024  	// Make a best-effort attempt to acquire the side lock, only to exclude
  2025  	// previous versions of the 'go' command from making simultaneous edits.
  2026  	if unlock, err := modfetch.SideLock(ctx); err == nil {
  2027  		defer unlock()
  2028  	}
  2029  
  2030  	err = lockedfile.Transform(modFilePath, func(old []byte) ([]byte, error) {
  2031  		if bytes.Equal(old, updatedGoMod) {
  2032  			// The go.mod file is already equal to new, possibly as the result of some
  2033  			// other process.
  2034  			return nil, errNoChange
  2035  		}
  2036  
  2037  		if index != nil && !bytes.Equal(old, index.data) {
  2038  			// The contents of the go.mod file have changed. In theory we could add all
  2039  			// of the new modules to the build list, recompute, and check whether any
  2040  			// module in *our* build list got bumped to a different version, but that's
  2041  			// a lot of work for marginal benefit. Instead, fail the command: if users
  2042  			// want to run concurrent commands, they need to start with a complete,
  2043  			// consistent module definition.
  2044  			return nil, fmt.Errorf("existing contents have changed since last read")
  2045  		}
  2046  
  2047  		return updatedGoMod, nil
  2048  	})
  2049  
  2050  	if err != nil && err != errNoChange {
  2051  		return fmt.Errorf("updating go.mod: %w", err)
  2052  	}
  2053  	return nil
  2054  }
  2055  
  2056  // keepSums returns the set of modules (and go.mod file entries) for which
  2057  // checksums would be needed in order to reload the same set of packages
  2058  // loaded by the most recent call to LoadPackages or ImportFromFiles,
  2059  // including any go.mod files needed to reconstruct the MVS result
  2060  // or identify go versions,
  2061  // in addition to the checksums for every module in keepMods.
  2062  func keepSums(loaderstate *State, ctx context.Context, ld *loader, rs *Requirements, which whichSums) map[module.Version]bool {
  2063  	// Every module in the full module graph contributes its requirements,
  2064  	// so in order to ensure that the build list itself is reproducible,
  2065  	// we need sums for every go.mod in the graph (regardless of whether
  2066  	// that version is selected).
  2067  	keep := make(map[module.Version]bool)
  2068  
  2069  	// Add entries for modules in the build list with paths that are prefixes of
  2070  	// paths of loaded packages. We need to retain sums for all of these modules —
  2071  	// not just the modules containing the actual packages — in order to rule out
  2072  	// ambiguous import errors the next time we load the package.
  2073  	keepModSumsForZipSums := true
  2074  	if ld == nil {
  2075  		if gover.Compare(loaderstate.MainModules.GoVersion(loaderstate), gover.TidyGoModSumVersion) < 0 && cfg.BuildMod != "mod" {
  2076  			keepModSumsForZipSums = false
  2077  		}
  2078  	} else {
  2079  		keepPkgGoModSums := true
  2080  		if gover.Compare(ld.requirements.GoVersion(loaderstate), gover.TidyGoModSumVersion) < 0 && (ld.Tidy || cfg.BuildMod != "mod") {
  2081  			keepPkgGoModSums = false
  2082  			keepModSumsForZipSums = false
  2083  		}
  2084  		for _, pkg := range ld.pkgs {
  2085  			// We check pkg.mod.Path here instead of pkg.inStd because the
  2086  			// pseudo-package "C" is not in std, but not provided by any module (and
  2087  			// shouldn't force loading the whole module graph).
  2088  			if pkg.testOf != nil || (pkg.mod.Path == "" && pkg.err == nil) || module.CheckImportPath(pkg.path) != nil {
  2089  				continue
  2090  			}
  2091  
  2092  			// We need the checksum for the go.mod file for pkg.mod
  2093  			// so that we know what Go version to use to compile pkg.
  2094  			// However, we didn't do so before Go 1.21, and the bug is relatively
  2095  			// minor, so we maintain the previous (buggy) behavior in 'go mod tidy' to
  2096  			// avoid introducing unnecessary churn.
  2097  			if keepPkgGoModSums {
  2098  				r := resolveReplacement(loaderstate, pkg.mod)
  2099  				keep[modkey(r)] = true
  2100  			}
  2101  
  2102  			if rs.pruning == pruned && pkg.mod.Path != "" {
  2103  				if v, ok := rs.rootSelected(loaderstate, pkg.mod.Path); ok && v == pkg.mod.Version {
  2104  					// pkg was loaded from a root module, and because the main module has
  2105  					// a pruned module graph we do not check non-root modules for
  2106  					// conflicts for packages that can be found in roots. So we only need
  2107  					// the checksums for the root modules that may contain pkg, not all
  2108  					// possible modules.
  2109  					for prefix := pkg.path; prefix != "."; prefix = path.Dir(prefix) {
  2110  						if v, ok := rs.rootSelected(loaderstate, prefix); ok && v != "none" {
  2111  							m := module.Version{Path: prefix, Version: v}
  2112  							r := resolveReplacement(loaderstate, m)
  2113  							keep[r] = true
  2114  						}
  2115  					}
  2116  					continue
  2117  				}
  2118  			}
  2119  
  2120  			mg, _ := rs.Graph(loaderstate, ctx)
  2121  			for prefix := pkg.path; prefix != "."; prefix = path.Dir(prefix) {
  2122  				if v := mg.Selected(prefix); v != "none" {
  2123  					m := module.Version{Path: prefix, Version: v}
  2124  					r := resolveReplacement(loaderstate, m)
  2125  					keep[r] = true
  2126  				}
  2127  			}
  2128  		}
  2129  	}
  2130  
  2131  	if rs.graph.Load() == nil {
  2132  		// We haven't needed to load the module graph so far.
  2133  		// Save sums for the root modules (or their replacements), but don't
  2134  		// incur the cost of loading the graph just to find and retain the sums.
  2135  		for _, m := range rs.rootModules {
  2136  			r := resolveReplacement(loaderstate, m)
  2137  			keep[modkey(r)] = true
  2138  			if which == addBuildListZipSums {
  2139  				keep[r] = true
  2140  			}
  2141  		}
  2142  	} else {
  2143  		mg, _ := rs.Graph(loaderstate, ctx)
  2144  		mg.WalkBreadthFirst(func(m module.Version) {
  2145  			if _, ok := mg.RequiredBy(m); ok {
  2146  				// The requirements from m's go.mod file are present in the module graph,
  2147  				// so they are relevant to the MVS result regardless of whether m was
  2148  				// actually selected.
  2149  				r := resolveReplacement(loaderstate, m)
  2150  				keep[modkey(r)] = true
  2151  			}
  2152  		})
  2153  
  2154  		if which == addBuildListZipSums {
  2155  			for _, m := range mg.BuildList() {
  2156  				r := resolveReplacement(loaderstate, m)
  2157  				if keepModSumsForZipSums {
  2158  					keep[modkey(r)] = true // we need the go version from the go.mod file to do anything useful with the zipfile
  2159  				}
  2160  				keep[r] = true
  2161  			}
  2162  		}
  2163  	}
  2164  
  2165  	return keep
  2166  }
  2167  
  2168  type whichSums int8
  2169  
  2170  const (
  2171  	loadedZipSumsOnly = whichSums(iota)
  2172  	addBuildListZipSums
  2173  )
  2174  
  2175  // modkey returns the module.Version under which the checksum for m's go.mod
  2176  // file is stored in the go.sum file.
  2177  func modkey(m module.Version) module.Version {
  2178  	return module.Version{Path: m.Path, Version: m.Version + "/go.mod"}
  2179  }
  2180  
  2181  func suggestModulePath(path string) string {
  2182  	var m string
  2183  
  2184  	i := len(path)
  2185  	for i > 0 && ('0' <= path[i-1] && path[i-1] <= '9' || path[i-1] == '.') {
  2186  		i--
  2187  	}
  2188  	url := path[:i]
  2189  	url = strings.TrimSuffix(url, "/v")
  2190  	url = strings.TrimSuffix(url, "/")
  2191  
  2192  	f := func(c rune) bool {
  2193  		return c > '9' || c < '0'
  2194  	}
  2195  	s := strings.FieldsFunc(path[i:], f)
  2196  	if len(s) > 0 {
  2197  		m = s[0]
  2198  	}
  2199  	m = strings.TrimLeft(m, "0")
  2200  	if m == "" || m == "1" {
  2201  		return url + "/v2"
  2202  	}
  2203  
  2204  	return url + "/v" + m
  2205  }
  2206  
  2207  func suggestGopkgIn(path string) string {
  2208  	var m string
  2209  	i := len(path)
  2210  	for i > 0 && (('0' <= path[i-1] && path[i-1] <= '9') || (path[i-1] == '.')) {
  2211  		i--
  2212  	}
  2213  	url := path[:i]
  2214  	url = strings.TrimSuffix(url, ".v")
  2215  	url = strings.TrimSuffix(url, "/v")
  2216  	url = strings.TrimSuffix(url, "/")
  2217  
  2218  	f := func(c rune) bool {
  2219  		return c > '9' || c < '0'
  2220  	}
  2221  	s := strings.FieldsFunc(path, f)
  2222  	if len(s) > 0 {
  2223  		m = s[0]
  2224  	}
  2225  
  2226  	m = strings.TrimLeft(m, "0")
  2227  
  2228  	if m == "" {
  2229  		return url + ".v1"
  2230  	}
  2231  	return url + ".v" + m
  2232  }
  2233  
  2234  func CheckGodebug(verb, k, v string) error {
  2235  	if strings.ContainsAny(k, " \t") {
  2236  		return fmt.Errorf("key contains space")
  2237  	}
  2238  	if strings.ContainsAny(v, " \t") {
  2239  		return fmt.Errorf("value contains space")
  2240  	}
  2241  	if strings.ContainsAny(k, ",") {
  2242  		return fmt.Errorf("key contains comma")
  2243  	}
  2244  	if strings.ContainsAny(v, ",") {
  2245  		return fmt.Errorf("value contains comma")
  2246  	}
  2247  	if k == "default" {
  2248  		if !strings.HasPrefix(v, "go") || !gover.IsValid(v[len("go"):]) {
  2249  			return fmt.Errorf("value for default= must be goVERSION")
  2250  		}
  2251  		if gover.Compare(v[len("go"):], gover.Local()) > 0 {
  2252  			return fmt.Errorf("default=%s too new (toolchain is go%s)", v, gover.Local())
  2253  		}
  2254  		return nil
  2255  	}
  2256  	if godebugs.Lookup(k) != nil {
  2257  		return nil
  2258  	}
  2259  	for _, info := range godebugs.Removed {
  2260  		if info.Name == k {
  2261  			return fmt.Errorf("use of removed %s %q, see https://go.dev/doc/godebug#go-1%v", verb, k, info.Removed)
  2262  		}
  2263  	}
  2264  	return fmt.Errorf("unknown %s %q", verb, k)
  2265  }
  2266  

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