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.
7 // This file contains the module-mode package loader, as well as some accessory
8 // functions pertaining to the package import graph.
10 // There are two exported entry points into package loading — LoadPackages and
11 // ImportFromFiles — both implemented in terms of loadFromRoots, which itself
12 // manipulates an instance of the loader struct.
14 // Although most of the loading state is maintained in the loader struct,
15 // one key piece - the build list - is a global, so that it can be modified
16 // separate from the loading operation, such as during "go get"
17 // upgrades/downgrades or in "go mod" operations.
18 // TODO(#40775): It might be nice to make the loader take and return
19 // a buildList rather than hard-coding use of the global.
21 // Loading is an iterative process. On each iteration, we try to load the
22 // requested packages and their transitive imports, then try to resolve modules
23 // for any imported packages that are still missing.
25 // The first step of each iteration identifies a set of “root” packages.
26 // Normally the root packages are exactly those matching the named pattern
27 // arguments. However, for the "all" meta-pattern, the final set of packages is
28 // computed from the package import graph, and therefore cannot be an initial
29 // input to loading that graph. Instead, the root packages for the "all" pattern
30 // are those contained in the main module, and allPatternIsRoot parameter to the
31 // loader instructs it to dynamically expand those roots to the full "all"
32 // pattern as loading progresses.
34 // The pkgInAll flag on each loadPkg instance tracks whether that
35 // package is known to match the "all" meta-pattern.
36 // A package matches the "all" pattern if:
37 // - it is in the main module, or
38 // - it is imported by any test in the main module, or
39 // - it is imported by another package in "all", or
40 // - the main module specifies a go version ≤ 1.15, and the package is imported
41 // by a *test of* another package in "all".
43 // When graph pruning is in effect, we want to spot-check the graph-pruning
44 // invariants — which depend on which packages are known to be in "all" — even
45 // when we are only loading individual packages, so we set the pkgInAll flag
46 // regardless of the whether the "all" pattern is a root.
47 // (This is necessary to maintain the “import invariant” described in
48 // https://golang.org/design/36460-lazy-module-loading.)
50 // Because "go mod vendor" prunes out the tests of vendored packages, the
51 // behavior of the "all" pattern with -mod=vendor in Go 1.11–1.15 is the same
52 // as the "all" pattern (regardless of the -mod flag) in 1.16+.
53 // The loader uses the GoVersion parameter to determine whether the "all"
54 // pattern should close over tests (as in Go 1.11–1.15) or stop at only those
55 // packages transitively imported by the packages and tests in the main module
56 // ("all" in Go 1.16+ and "go mod vendor" in Go 1.11+).
58 // Note that it is possible for a loaded package NOT to be in "all" even when we
59 // are loading the "all" pattern. For example, packages that are transitive
60 // dependencies of other roots named on the command line must be loaded, but are
61 // not in "all". (The mod_notall test illustrates this behavior.)
62 // Similarly, if the LoadTests flag is set but the "all" pattern does not close
63 // over test dependencies, then when we load the test of a package that is in
64 // "all" but outside the main module, the dependencies of that test will not
65 // necessarily themselves be in "all". (That configuration does not arise in Go
66 // 1.11–1.15, but it will be possible in Go 1.16+.)
68 // Loading proceeds from the roots, using a parallel work-queue with a limit on
69 // the amount of active work (to avoid saturating disks, CPU cores, and/or
70 // network connections). Each package is added to the queue the first time it is
71 // imported by another package. When we have finished identifying the imports of
72 // a package, we add the test for that package if it is needed. A test may be
74 // - the package matches a root pattern and tests of the roots were requested, or
75 // - the package is in the main module and the "all" pattern is requested
76 // (because the "all" pattern includes the dependencies of tests in the main
78 // - the package is in "all" and the definition of "all" we are using includes
79 // dependencies of tests (as is the case in Go ≤1.15).
81 // After all available packages have been loaded, we examine the results to
82 // identify any requested or imported packages that are still missing, and if
83 // so, which modules we could add to the module graph in order to make the
84 // missing packages available. We add those to the module graph and iterate,
85 // until either all packages resolve successfully or we cannot identify any
86 // module that would resolve any remaining missing package.
88 // If the main module is “tidy” (that is, if "go mod tidy" is a no-op for it)
89 // and all requested packages are in "all", then loading completes in a single
91 // TODO(bcmills): We should also be able to load in a single iteration if the
92 // requested packages all come from modules that are themselves tidy, regardless
93 // of whether those packages are in "all". Today, that requires two iterations
94 // if those packages are not found in existing dependencies of the main module.
113 "cmd/go/internal/base"
114 "cmd/go/internal/cfg"
115 "cmd/go/internal/fsys"
116 "cmd/go/internal/imports"
117 "cmd/go/internal/modfetch"
118 "cmd/go/internal/modindex"
119 "cmd/go/internal/mvs"
120 "cmd/go/internal/par"
121 "cmd/go/internal/search"
122 "cmd/go/internal/str"
124 "golang.org/x/mod/module"
125 "golang.org/x/mod/semver"
128 // loaded is the most recently-used package loader.
129 // It holds details about individual packages.
131 // This variable should only be accessed directly in top-level exported
132 // functions. All other functions that require or produce a *loader should pass
133 // or return it as an explicit parameter.
136 // PackageOpts control the behavior of the LoadPackages function.
137 type PackageOpts struct {
138 // GoVersion is the Go version to which the go.mod file should be updated
139 // after packages have been loaded.
141 // An empty GoVersion means to use the Go version already specified in the
142 // main module's go.mod file, or the latest Go version if there is no main
146 // Tags are the build tags in effect (as interpreted by the
147 // cmd/go/internal/imports package).
148 // If nil, treated as equivalent to imports.Tags().
151 // Tidy, if true, requests that the build list and go.sum file be reduced to
152 // the minimial dependencies needed to reproducibly reload the requested
156 // TidyCompatibleVersion is the oldest Go version that must be able to
157 // reproducibly reload the requested packages.
159 // If empty, the compatible version is the Go version immediately prior to the
160 // 'go' version listed in the go.mod file.
161 TidyCompatibleVersion string
163 // VendorModulesInGOROOTSrc indicates that if we are within a module in
164 // GOROOT/src, packages in the module's vendor directory should be resolved as
165 // actual module dependencies (instead of standard-library packages).
166 VendorModulesInGOROOTSrc bool
168 // ResolveMissingImports indicates that we should attempt to add module
169 // dependencies as needed to resolve imports of packages that are not found.
171 // For commands that support the -mod flag, resolving imports may still fail
172 // if the flag is set to "readonly" (the default) or "vendor".
173 ResolveMissingImports bool
175 // AssumeRootsImported indicates that the transitive dependencies of the root
176 // packages should be treated as if those roots will be imported by the main
178 AssumeRootsImported bool
180 // AllowPackage, if non-nil, is called after identifying the module providing
181 // each package. If AllowPackage returns a non-nil error, that error is set
182 // for the package, and the imports and test of that package will not be
185 // AllowPackage may be invoked concurrently by multiple goroutines,
186 // and may be invoked multiple times for a given package path.
187 AllowPackage func(ctx context.Context, path string, mod module.Version) error
189 // LoadTests loads the test dependencies of each package matching a requested
190 // pattern. If ResolveMissingImports is also true, test dependencies will be
191 // resolved if missing.
194 // UseVendorAll causes the "all" package pattern to be interpreted as if
195 // running "go mod vendor" (or building with "-mod=vendor").
197 // This is a no-op for modules that declare 'go 1.16' or higher, for which this
198 // is the default (and only) interpretation of the "all" pattern in module mode.
201 // AllowErrors indicates that LoadPackages should not terminate the process if
205 // SilencePackageErrors indicates that LoadPackages should not print errors
206 // that occur while matching or loading packages, and should not terminate the
207 // process if such an error occurs.
209 // Errors encountered in the module graph will still be reported.
211 // The caller may retrieve the silenced package errors using the Lookup
212 // function, and matching errors are still populated in the Errs field of the
213 // associated search.Match.)
214 SilencePackageErrors bool
216 // SilenceMissingStdImports indicates that LoadPackages should not print
217 // errors or terminate the process if an imported package is missing, and the
218 // import path looks like it might be in the standard library (perhaps in a
220 SilenceMissingStdImports bool
222 // SilenceNoGoErrors indicates that LoadPackages should not print
223 // imports.ErrNoGo errors.
224 // This allows the caller to invoke LoadPackages (and report other errors)
225 // without knowing whether the requested packages exist for the given tags.
227 // Note that if a requested package does not exist *at all*, it will fail
228 // during module resolution and the error will not be suppressed.
229 SilenceNoGoErrors bool
231 // SilenceUnmatchedWarnings suppresses the warnings normally emitted for
232 // patterns that did not match any packages.
233 SilenceUnmatchedWarnings bool
235 // Resolve the query against this module.
236 MainModule module.Version
239 // LoadPackages identifies the set of packages matching the given patterns and
240 // loads the packages in the import graph rooted at that set.
241 func LoadPackages(ctx context.Context, opts PackageOpts, patterns ...string) (matches []*search.Match, loadedPackages []string) {
242 if opts.Tags == nil {
243 opts.Tags = imports.Tags()
246 patterns = search.CleanPatterns(patterns)
247 matches = make([]*search.Match, 0, len(patterns))
248 allPatternIsRoot := false
249 for _, pattern := range patterns {
250 matches = append(matches, search.NewMatch(pattern))
251 if pattern == "all" {
252 allPatternIsRoot = true
256 updateMatches := func(rs *Requirements, ld *loader) {
257 for _, m := range matches {
260 // Evaluate list of file system directories on first iteration.
262 matchModRoots := modRoots
263 if opts.MainModule != (module.Version{}) {
264 matchModRoots = []string{MainModules.ModRoot(opts.MainModule)}
266 matchLocalDirs(ctx, matchModRoots, m, rs)
269 // Make a copy of the directory list and translate to import paths.
270 // Note that whether a directory corresponds to an import path
271 // changes as the build list is updated, and a directory can change
272 // from not being in the build list to being in it and back as
273 // the exact version of a particular module increases during
274 // the loader iterations.
276 for _, dir := range m.Dirs {
277 pkg, err := resolveLocalPackage(ctx, dir, rs)
279 if !m.IsLiteral() && (err == errPkgIsBuiltin || err == errPkgIsGorootSrc) {
280 continue // Don't include "builtin" or GOROOT/src in wildcard patterns.
283 // If we're outside of a module, ensure that the failure mode
294 m.Pkgs = append(m.Pkgs, pkg)
298 m.Pkgs = []string{m.Pattern()}
300 case strings.Contains(m.Pattern(), "..."):
302 mg, err := rs.Graph(ctx)
304 // The module graph is (or may be) incomplete — perhaps we failed to
305 // load the requirements of some module. This is an error in matching
306 // the patterns to packages, because we may be missing some packages
307 // or we may erroneously match packages in the wrong versions of
308 // modules. However, for cases like 'go list -e', the error should not
309 // necessarily prevent us from loading the packages we could find.
310 m.Errs = append(m.Errs, err)
312 matchPackages(ctx, m, opts.Tags, includeStd, mg.BuildList())
314 case m.Pattern() == "all":
316 // The initial roots are the packages in the main module.
317 // loadFromRoots will expand that to "all".
319 matchModules := MainModules.Versions()
320 if opts.MainModule != (module.Version{}) {
321 matchModules = []module.Version{opts.MainModule}
323 matchPackages(ctx, m, opts.Tags, omitStd, matchModules)
325 // Starting with the packages in the main module,
326 // enumerate the full list of "all".
327 m.Pkgs = ld.computePatternAll()
330 case m.Pattern() == "std" || m.Pattern() == "cmd":
332 m.MatchPackages() // Locate the packages within GOROOT/src.
336 panic(fmt.Sprintf("internal error: modload missing case for pattern %s", m.Pattern()))
341 initialRS := LoadModFile(ctx)
343 ld := loadFromRoots(ctx, loaderParams{
345 requirements: initialRS,
347 allPatternIsRoot: allPatternIsRoot,
349 listRoots: func(rs *Requirements) (roots []string) {
350 updateMatches(rs, nil)
351 for _, m := range matches {
352 roots = append(roots, m.Pkgs...)
358 // One last pass to finalize wildcards.
359 updateMatches(ld.requirements, ld)
361 // List errors in matching patterns (such as directory permission
362 // errors for wildcard patterns).
363 if !ld.SilencePackageErrors {
364 for _, match := range matches {
365 for _, err := range match.Errs {
366 ld.errorf("%v\n", err)
372 if !opts.SilenceUnmatchedWarnings {
373 search.WarnUnmatched(matches)
378 mg, _ := ld.requirements.Graph(ctx)
380 for _, m := range initialRS.rootModules {
382 if ld.requirements.pruning == unpruned {
383 // m is unused if it was dropped from the module graph entirely. If it
384 // was only demoted from direct to indirect, it may still be in use via
385 // a transitive import.
386 unused = mg.Selected(m.Path) == "none"
388 // m is unused if it was dropped from the roots. If it is still present
389 // as a transitive dependency, that transitive dependency is not needed
390 // by any package or test in the main module.
391 _, ok := ld.requirements.rootSelected(m.Path)
395 fmt.Fprintf(os.Stderr, "unused %s\n", m.Path)
400 keep := keepSums(ctx, ld, ld.requirements, loadedZipSumsOnly)
401 if compatDepth := pruningForGoVersion(ld.TidyCompatibleVersion); compatDepth != ld.requirements.pruning {
402 compatRS := newRequirements(compatDepth, ld.requirements.rootModules, ld.requirements.direct)
403 ld.checkTidyCompatibility(ctx, compatRS)
405 for m := range keepSums(ctx, ld, compatRS, loadedZipSumsOnly) {
410 if !ExplicitWriteGoMod {
411 modfetch.TrimGoSum(keep)
413 // commitRequirements below will also call WriteGoSum, but the "keep" map
414 // we have here could be strictly larger: commitRequirements only commits
415 // loaded.requirements, but here we may have also loaded (and want to
416 // preserve checksums for) additional entities from compatRS, which are
417 // only needed for compatibility with ld.TidyCompatibleVersion.
418 if err := modfetch.WriteGoSum(keep, mustHaveCompleteRequirements()); err != nil {
419 base.Fatalf("go: %v", err)
423 // Update the go.mod file's Go version if necessary.
424 if modFile := ModFile(); modFile != nil && ld.GoVersion != "" {
425 modFile.AddGoStmt(ld.GoVersion)
429 // Success! Update go.mod and go.sum (if needed) and return the results.
430 // We'll skip updating if ExplicitWriteGoMod is true (the caller has opted
431 // to call WriteGoMod itself) or if ResolveMissingImports is false (the
432 // command wants to examine the package graph as-is).
434 requirements = loaded.requirements
436 for _, pkg := range ld.pkgs {
438 loadedPackages = append(loadedPackages, pkg.path)
441 sort.Strings(loadedPackages)
443 if !ExplicitWriteGoMod && opts.ResolveMissingImports {
444 if err := commitRequirements(ctx); err != nil {
445 base.Fatalf("go: %v", err)
449 return matches, loadedPackages
452 // matchLocalDirs is like m.MatchDirs, but tries to avoid scanning directories
453 // outside of the standard library and active modules.
454 func matchLocalDirs(ctx context.Context, modRoots []string, m *search.Match, rs *Requirements) {
456 panic(fmt.Sprintf("internal error: resolveLocalDirs on non-local pattern %s", m.Pattern()))
459 if i := strings.Index(m.Pattern(), "..."); i >= 0 {
460 // The pattern is local, but it is a wildcard. Its packages will
461 // only resolve to paths if they are inside of the standard
462 // library, the main module, or some dependency of the main
463 // module. Verify that before we walk the filesystem: a filesystem
464 // walk in a directory like /var or /etc can be very expensive!
465 dir := filepath.Dir(filepath.Clean(m.Pattern()[:i+3]))
467 if !filepath.IsAbs(dir) {
468 absDir = filepath.Join(base.Cwd(), dir)
471 modRoot := findModuleRoot(absDir)
473 for _, mainModuleRoot := range modRoots {
474 if mainModuleRoot == modRoot {
479 if !found && search.InDir(absDir, cfg.GOROOTsrc) == "" && pathInModuleCache(ctx, absDir, rs) == "" {
481 scope := "main module or its selected dependencies"
482 if inWorkspaceMode() {
483 scope = "modules listed in go.work or their selected dependencies"
485 m.AddError(fmt.Errorf("directory prefix %s does not contain %s", base.ShortPath(absDir), scope))
490 m.MatchDirs(modRoots)
493 // resolveLocalPackage resolves a filesystem path to a package path.
494 func resolveLocalPackage(ctx context.Context, dir string, rs *Requirements) (string, error) {
496 if filepath.IsAbs(dir) {
497 absDir = filepath.Clean(dir)
499 absDir = filepath.Join(base.Cwd(), dir)
502 bp, err := cfg.BuildContext.ImportDir(absDir, 0)
503 if err != nil && (bp == nil || len(bp.IgnoredGoFiles) == 0) {
504 // golang.org/issue/32917: We should resolve a relative path to a
505 // package path only if the relative path actually contains the code
508 // If the named directory does not exist or contains no Go files,
509 // the package does not exist.
510 // Other errors may affect package loading, but not resolution.
511 if _, err := fsys.Stat(absDir); err != nil {
512 if os.IsNotExist(err) {
513 // Canonicalize OS-specific errors to errDirectoryNotFound so that error
514 // messages will be easier for users to search for.
515 return "", &fs.PathError{Op: "stat", Path: absDir, Err: errDirectoryNotFound}
519 if _, noGo := err.(*build.NoGoError); noGo {
520 // A directory that does not contain any Go source files — even ignored
521 // ones! — is not a Go package, and we can't resolve it to a package
522 // path because that path could plausibly be provided by some other
525 // Any other error indicates that the package “exists” (at least in the
526 // sense that it cannot exist in any other module), but has some other
527 // problem (such as a syntax error).
532 for _, mod := range MainModules.Versions() {
533 modRoot := MainModules.ModRoot(mod)
534 if modRoot != "" && absDir == modRoot {
535 if absDir == cfg.GOROOTsrc {
536 return "", errPkgIsGorootSrc
538 return MainModules.PathPrefix(mod), nil
542 // Note: The checks for @ here are just to avoid misinterpreting
543 // the module cache directories (formerly GOPATH/src/mod/foo@v1.5.2/bar).
544 // It's not strictly necessary but helpful to keep the checks.
545 var pkgNotFoundErr error
546 pkgNotFoundLongestPrefix := ""
547 for _, mainModule := range MainModules.Versions() {
548 modRoot := MainModules.ModRoot(mainModule)
549 if modRoot != "" && strings.HasPrefix(absDir, modRoot+string(filepath.Separator)) && !strings.Contains(absDir[len(modRoot):], "@") {
550 suffix := filepath.ToSlash(absDir[len(modRoot):])
551 if pkg, found := strings.CutPrefix(suffix, "/vendor/"); found {
552 if cfg.BuildMod != "vendor" {
553 return "", fmt.Errorf("without -mod=vendor, directory %s has no package path", absDir)
556 readVendorList(mainModule)
557 if _, ok := vendorPkgModule[pkg]; !ok {
558 return "", fmt.Errorf("directory %s is not a package listed in vendor/modules.txt", absDir)
563 mainModulePrefix := MainModules.PathPrefix(mainModule)
564 if mainModulePrefix == "" {
565 pkg := strings.TrimPrefix(suffix, "/")
566 if pkg == "builtin" {
567 // "builtin" is a pseudo-package with a real source file.
568 // It's not included in "std", so it shouldn't resolve from "."
569 // within module "std" either.
570 return "", errPkgIsBuiltin
575 pkg := mainModulePrefix + suffix
576 if _, ok, err := dirInModule(pkg, mainModulePrefix, modRoot, true); err != nil {
579 // This main module could contain the directory but doesn't. Other main
580 // modules might contain the directory, so wait till we finish the loop
581 // to see if another main module contains directory. But if not,
583 if len(mainModulePrefix) > len(pkgNotFoundLongestPrefix) {
584 pkgNotFoundLongestPrefix = mainModulePrefix
585 pkgNotFoundErr = &PackageNotInModuleError{MainModules: []module.Version{mainModule}, Pattern: pkg}
592 if pkgNotFoundErr != nil {
593 return "", pkgNotFoundErr
596 if sub := search.InDir(absDir, cfg.GOROOTsrc); sub != "" && sub != "." && !strings.Contains(sub, "@") {
597 pkg := filepath.ToSlash(sub)
598 if pkg == "builtin" {
599 return "", errPkgIsBuiltin
604 pkg := pathInModuleCache(ctx, absDir, rs)
606 if inWorkspaceMode() {
607 if mr := findModuleRoot(absDir); mr != "" {
608 return "", fmt.Errorf("directory %s is contained in a module that is not one of the workspace modules listed in go.work. You can add the module to the workspace using:\n\tgo work use %s", base.ShortPath(absDir), base.ShortPath(mr))
610 return "", fmt.Errorf("directory %s outside modules listed in go.work or their selected dependencies", base.ShortPath(absDir))
612 return "", fmt.Errorf("directory %s outside main module or its selected dependencies", base.ShortPath(absDir))
618 errDirectoryNotFound = errors.New("directory not found")
619 errPkgIsGorootSrc = errors.New("GOROOT/src is not an importable package")
620 errPkgIsBuiltin = errors.New(`"builtin" is a pseudo-package, not an importable package`)
623 // pathInModuleCache returns the import path of the directory dir,
624 // if dir is in the module cache copy of a module in our build list.
625 func pathInModuleCache(ctx context.Context, dir string, rs *Requirements) string {
626 tryMod := func(m module.Version) (string, bool) {
629 if repl := Replacement(m); repl.Path != "" && repl.Version == "" {
631 if !filepath.IsAbs(root) {
632 root = filepath.Join(replaceRelativeTo(), root)
634 } else if repl.Path != "" {
635 root, err = modfetch.DownloadDir(repl)
637 root, err = modfetch.DownloadDir(m)
643 sub := search.InDir(dir, root)
647 sub = filepath.ToSlash(sub)
648 if strings.Contains(sub, "/vendor/") || strings.HasPrefix(sub, "vendor/") || strings.Contains(sub, "@") {
652 return path.Join(m.Path, filepath.ToSlash(sub)), true
655 if rs.pruning == pruned {
656 for _, m := range rs.rootModules {
657 if v, _ := rs.rootSelected(m.Path); v != m.Version {
658 continue // m is a root, but we have a higher root for the same path.
660 if importPath, ok := tryMod(m); ok {
661 // checkMultiplePaths ensures that a module can be used for at most one
662 // requirement, so this must be it.
668 // None of the roots contained dir, or the graph is unpruned (so we don't want
669 // to distinguish between roots and transitive dependencies). Either way,
670 // check the full graph to see if the directory is a non-root dependency.
672 // If the roots are not consistent with the full module graph, the selected
673 // versions of root modules may differ from what we already checked above.
674 // Re-check those paths too.
676 mg, _ := rs.Graph(ctx)
677 var importPath string
678 for _, m := range mg.BuildList() {
680 importPath, found = tryMod(m)
688 // ImportFromFiles adds modules to the build list as needed
689 // to satisfy the imports in the named Go source files.
691 // Errors in missing dependencies are silenced.
693 // TODO(bcmills): Silencing errors seems off. Take a closer look at this and
694 // figure out what the error-reporting actually ought to be.
695 func ImportFromFiles(ctx context.Context, gofiles []string) {
696 rs := LoadModFile(ctx)
698 tags := imports.Tags()
699 imports, testImports, err := imports.ScanFiles(gofiles, tags)
701 base.Fatalf("go: %v", err)
704 loaded = loadFromRoots(ctx, loaderParams{
705 PackageOpts: PackageOpts{
707 ResolveMissingImports: true,
708 SilencePackageErrors: true,
711 listRoots: func(*Requirements) (roots []string) {
712 roots = append(roots, imports...)
713 roots = append(roots, testImports...)
717 requirements = loaded.requirements
719 if !ExplicitWriteGoMod {
720 if err := commitRequirements(ctx); err != nil {
721 base.Fatalf("go: %v", err)
726 // DirImportPath returns the effective import path for dir,
727 // provided it is within a main module, or else returns ".".
728 func (mms *MainModuleSet) DirImportPath(ctx context.Context, dir string) (path string, m module.Version) {
730 return ".", module.Version{}
732 LoadModFile(ctx) // Sets targetPrefix.
734 if !filepath.IsAbs(dir) {
735 dir = filepath.Join(base.Cwd(), dir)
737 dir = filepath.Clean(dir)
740 var longestPrefix string
741 var longestPrefixPath string
742 var longestPrefixVersion module.Version
743 for _, v := range mms.Versions() {
744 modRoot := mms.ModRoot(v)
746 return mms.PathPrefix(v), v
748 if strings.HasPrefix(dir, modRoot+string(filepath.Separator)) {
749 pathPrefix := MainModules.PathPrefix(v)
750 if pathPrefix > longestPrefix {
751 longestPrefix = pathPrefix
752 longestPrefixVersion = v
753 suffix := filepath.ToSlash(dir[len(modRoot):])
754 if strings.HasPrefix(suffix, "/vendor/") {
755 longestPrefixPath = strings.TrimPrefix(suffix, "/vendor/")
758 longestPrefixPath = mms.PathPrefix(v) + suffix
762 if len(longestPrefix) > 0 {
763 return longestPrefixPath, longestPrefixVersion
766 return ".", module.Version{}
769 // PackageModule returns the module providing the package named by the import path.
770 func PackageModule(path string) module.Version {
771 pkg, ok := loaded.pkgCache.Get(path).(*loadPkg)
773 return module.Version{}
778 // Lookup returns the source directory, import path, and any loading error for
779 // the package at path as imported from the package in parentDir.
780 // Lookup requires that one of the Load functions in this package has already
782 func Lookup(parentPath string, parentIsStd bool, path string) (dir, realPath string, err error) {
784 panic("Lookup called with empty package path")
788 path = loaded.stdVendor(parentPath, path)
790 pkg, ok := loaded.pkgCache.Get(path).(*loadPkg)
792 // The loader should have found all the relevant paths.
793 // There are a few exceptions, though:
794 // - during go list without -test, the p.Resolve calls to process p.TestImports and p.XTestImports
795 // end up here to canonicalize the import paths.
796 // - during any load, non-loaded packages like "unsafe" end up here.
797 // - during any load, build-injected dependencies like "runtime/cgo" end up here.
798 // - because we ignore appengine/* in the module loader,
799 // the dependencies of any actual appengine/* library end up here.
800 dir := findStandardImportPath(path)
802 return dir, path, nil
804 return "", "", errMissing
806 return pkg.dir, pkg.path, pkg.err
809 // A loader manages the process of loading information about
810 // the required packages for a particular build,
811 // checking that the packages are available in the module set,
812 // and updating the module set if needed.
816 // allClosesOverTests indicates whether the "all" pattern includes
817 // dependencies of tests outside the main module (as in Go 1.11–1.15).
818 // (Otherwise — as in Go 1.16+ — the "all" pattern includes only the packages
819 // transitively *imported by* the packages and tests in the main module.)
820 allClosesOverTests bool
824 // reset on each iteration
826 pkgCache *par.Cache // package path (string) → *loadPkg
827 pkgs []*loadPkg // transitive closure of loaded packages and tests; populated in buildStacks
830 // loaderParams configure the packages loaded by, and the properties reported
831 // by, a loader instance.
832 type loaderParams struct {
834 requirements *Requirements
836 allPatternIsRoot bool // Is the "all" pattern an additional root?
838 listRoots func(rs *Requirements) []string
841 func (ld *loader) reset() {
843 case <-ld.work.Idle():
845 panic("loader.reset when not idle")
849 ld.pkgCache = new(par.Cache)
853 // errorf reports an error via either os.Stderr or base.Errorf,
854 // according to whether ld.AllowErrors is set.
855 func (ld *loader) errorf(format string, args ...any) {
857 fmt.Fprintf(os.Stderr, format, args...)
859 base.Errorf(format, args...)
863 // A loadPkg records information about a single loaded package.
864 type loadPkg struct {
865 // Populated at construction time:
866 path string // import path
869 // Populated at construction time and updated by (*loader).applyPkgFlags:
870 flags atomicLoadPkgFlags
872 // Populated by (*loader).load:
873 mod module.Version // module providing package
874 dir string // directory containing source code
875 err error // error loading package
876 imports []*loadPkg // packages imported by this one
877 testImports []string // test-only imports, saved for use by pkg.test.
879 altMods []module.Version // modules that could have contained the package but did not
881 // Populated by (*loader).pkgTest:
885 // Populated by postprocessing in (*loader).buildStacks:
886 stack *loadPkg // package importing this one in minimal import stack for this pkg
889 // loadPkgFlags is a set of flags tracking metadata about a package.
890 type loadPkgFlags int8
893 // pkgInAll indicates that the package is in the "all" package pattern,
894 // regardless of whether we are loading the "all" package pattern.
896 // When the pkgInAll flag and pkgImportsLoaded flags are both set, the caller
897 // who set the last of those flags must propagate the pkgInAll marking to all
898 // of the imports of the marked package.
900 // A test is marked with pkgInAll if that test would promote the packages it
901 // imports to be in "all" (such as when the test is itself within the main
902 // module, or when ld.allClosesOverTests is true).
903 pkgInAll loadPkgFlags = 1 << iota
905 // pkgIsRoot indicates that the package matches one of the root package
906 // patterns requested by the caller.
908 // If LoadTests is set, then when pkgIsRoot and pkgImportsLoaded are both set,
909 // the caller who set the last of those flags must populate a test for the
910 // package (in the pkg.test field).
912 // If the "all" pattern is included as a root, then non-test packages in "all"
913 // are also roots (and must be marked pkgIsRoot).
916 // pkgFromRoot indicates that the package is in the transitive closure of
917 // imports starting at the roots. (Note that every package marked as pkgIsRoot
918 // is also trivially marked pkgFromRoot.)
921 // pkgImportsLoaded indicates that the imports and testImports fields of a
922 // loadPkg have been populated.
926 // has reports whether all of the flags in cond are set in f.
927 func (f loadPkgFlags) has(cond loadPkgFlags) bool {
928 return f&cond == cond
931 // An atomicLoadPkgFlags stores a loadPkgFlags for which individual flags can be
933 type atomicLoadPkgFlags struct {
937 // update sets the given flags in af (in addition to any flags already set).
939 // update returns the previous flag state so that the caller may determine which
940 // flags were newly-set.
941 func (af *atomicLoadPkgFlags) update(flags loadPkgFlags) (old loadPkgFlags) {
943 old := af.bits.Load()
944 new := old | int32(flags)
945 if new == old || af.bits.CompareAndSwap(old, new) {
946 return loadPkgFlags(old)
951 // has reports whether all of the flags in cond are set in af.
952 func (af *atomicLoadPkgFlags) has(cond loadPkgFlags) bool {
953 return loadPkgFlags(af.bits.Load())&cond == cond
956 // isTest reports whether pkg is a test of another package.
957 func (pkg *loadPkg) isTest() bool {
958 return pkg.testOf != nil
961 // fromExternalModule reports whether pkg was loaded from a module other than
963 func (pkg *loadPkg) fromExternalModule() bool {
964 if pkg.mod.Path == "" {
965 return false // loaded from the standard library, not a module
967 return !MainModules.Contains(pkg.mod.Path)
970 var errMissing = errors.New("cannot find package")
972 // loadFromRoots attempts to load the build graph needed to process a set of
973 // root packages and their dependencies.
975 // The set of root packages is returned by the params.listRoots function, and
976 // expanded to the full set of packages by tracing imports (and possibly tests)
978 func loadFromRoots(ctx context.Context, params loaderParams) *loader {
980 loaderParams: params,
981 work: par.NewQueue(runtime.GOMAXPROCS(0)),
984 if ld.GoVersion == "" {
985 ld.GoVersion = MainModules.GoVersion()
987 if ld.Tidy && versionLess(LatestGoVersion(), ld.GoVersion) {
988 ld.errorf("go: go.mod file indicates go %s, but maximum version supported by tidy is %s\n", ld.GoVersion, LatestGoVersion())
994 if ld.TidyCompatibleVersion == "" {
995 ld.TidyCompatibleVersion = priorGoVersion(ld.GoVersion)
996 } else if versionLess(ld.GoVersion, ld.TidyCompatibleVersion) {
997 // Each version of the Go toolchain knows how to interpret go.mod and
998 // go.sum files produced by all previous versions, so a compatibility
999 // version higher than the go.mod version adds nothing.
1000 ld.TidyCompatibleVersion = ld.GoVersion
1004 if semver.Compare("v"+ld.GoVersion, narrowAllVersionV) < 0 && !ld.UseVendorAll {
1005 // The module's go version explicitly predates the change in "all" for graph
1006 // pruning, so continue to use the older interpretation.
1007 ld.allClosesOverTests = true
1011 desiredPruning := pruningForGoVersion(ld.GoVersion)
1012 if ld.requirements.pruning == workspace {
1013 desiredPruning = workspace
1015 ld.requirements, err = convertPruning(ctx, ld.requirements, desiredPruning)
1017 ld.errorf("go: %v\n", err)
1020 if ld.requirements.pruning == unpruned {
1021 // If the module graph does not support pruning, we assume that we will need
1022 // the full module graph in order to load package dependencies.
1024 // This might not be strictly necessary, but it matches the historical
1025 // behavior of the 'go' command and keeps the go.mod file more consistent in
1026 // case of erroneous hand-edits — which are less likely to be detected by
1027 // spot-checks in modules that do not maintain the expanded go.mod
1028 // requirements needed for graph pruning.
1030 ld.requirements, _, err = expandGraph(ctx, ld.requirements)
1032 ld.errorf("go: %v\n", err)
1039 // Load the root packages and their imports.
1040 // Note: the returned roots can change on each iteration,
1041 // since the expansion of package patterns depends on the
1042 // build list we're using.
1043 rootPkgs := ld.listRoots(ld.requirements)
1045 if ld.requirements.pruning == pruned && cfg.BuildMod == "mod" {
1046 // Before we start loading transitive imports of packages, locate all of
1047 // the root packages and promote their containing modules to root modules
1048 // dependencies. If their go.mod files are tidy (the common case) and the
1049 // set of root packages does not change then we can select the correct
1050 // versions of all transitive imports on the first try and complete
1051 // loading in a single iteration.
1052 changedBuildList := ld.preloadRootModules(ctx, rootPkgs)
1053 if changedBuildList {
1054 // The build list has changed, so the set of root packages may have also
1055 // changed. Start over to pick up the changes. (Preloading roots is much
1056 // cheaper than loading the full import graph, so we would rather pay
1057 // for an extra iteration of preloading than potentially end up
1058 // discarding the result of a full iteration of loading.)
1063 inRoots := map[*loadPkg]bool{}
1064 for _, path := range rootPkgs {
1065 root := ld.pkg(ctx, path, pkgIsRoot)
1067 ld.roots = append(ld.roots, root)
1068 inRoots[root] = true
1072 // ld.pkg adds imported packages to the work queue and calls applyPkgFlags,
1073 // which adds tests (and test dependencies) as needed.
1075 // When all of the work in the queue has completed, we'll know that the
1076 // transitive closure of dependencies has been loaded.
1081 changed, err := ld.updateRequirements(ctx)
1083 ld.errorf("go: %v\n", err)
1087 // Don't resolve missing imports until the module graph has stabilized.
1088 // If the roots are still changing, they may turn out to specify a
1089 // requirement on the missing package(s), and we would rather use a
1090 // version specified by a new root than add a new dependency on an
1091 // unrelated version.
1095 if !ld.ResolveMissingImports || (!HasModRoot() && !allowMissingModuleImports) {
1096 // We've loaded as much as we can without resolving missing imports.
1100 modAddedBy := ld.resolveMissingImports(ctx)
1101 if len(modAddedBy) == 0 {
1102 // The roots are stable, and we've resolved all of the missing packages
1107 toAdd := make([]module.Version, 0, len(modAddedBy))
1108 for m := range modAddedBy {
1109 toAdd = append(toAdd, m)
1111 module.Sort(toAdd) // to make errors deterministic
1113 // We ran updateRequirements before resolving missing imports and it didn't
1114 // make any changes, so we know that the requirement graph is already
1115 // consistent with ld.pkgs: we don't need to pass ld.pkgs to updateRoots
1116 // again. (That would waste time looking for changes that we have already
1118 var noPkgs []*loadPkg
1119 // We also know that we're going to call updateRequirements again next
1120 // iteration so we don't need to also update it here. (That would waste time
1121 // computing a "direct" map that we'll have to recompute later anyway.)
1122 direct := ld.requirements.direct
1123 rs, err := updateRoots(ctx, direct, ld.requirements, noPkgs, toAdd, ld.AssumeRootsImported)
1125 // If an error was found in a newly added module, report the package
1126 // import stack instead of the module requirement stack. Packages
1127 // are more descriptive.
1128 if err, ok := err.(*mvs.BuildListError); ok {
1129 if pkg := modAddedBy[err.Module()]; pkg != nil {
1130 ld.errorf("go: %s: %v\n", pkg.stackText(), err.Err)
1134 ld.errorf("go: %v\n", err)
1137 if reflect.DeepEqual(rs.rootModules, ld.requirements.rootModules) {
1138 // Something is deeply wrong. resolveMissingImports gave us a non-empty
1139 // set of modules to add to the graph, but adding those modules had no
1140 // effect — either they were already in the graph, or updateRoots did not
1141 // add them as requested.
1142 panic(fmt.Sprintf("internal error: adding %v to module graph had no effect on root requirements (%v)", toAdd, rs.rootModules))
1144 ld.requirements = rs
1146 base.ExitIfErrors() // TODO(bcmills): Is this actually needed?
1148 // Tidy the build list, if applicable, before we report errors.
1149 // (The process of tidying may remove errors from irrelevant dependencies.)
1151 rs, err := tidyRoots(ctx, ld.requirements, ld.pkgs)
1153 ld.errorf("go: %v\n", err)
1156 if ld.requirements.pruning == pruned {
1157 // We continuously add tidy roots to ld.requirements during loading, so at
1158 // this point the tidy roots should be a subset of the roots of
1159 // ld.requirements, ensuring that no new dependencies are brought inside
1160 // the graph-pruning horizon.
1161 // If that is not the case, there is a bug in the loading loop above.
1162 for _, m := range rs.rootModules {
1163 if v, ok := ld.requirements.rootSelected(m.Path); !ok || v != m.Version {
1164 ld.errorf("go: internal error: a requirement on %v is needed but was not added during package loading\n", m)
1169 ld.requirements = rs
1173 // Report errors, if any.
1174 for _, pkg := range ld.pkgs {
1179 // Add importer information to checksum errors.
1180 if sumErr := (*ImportMissingSumError)(nil); errors.As(pkg.err, &sumErr) {
1181 if importer := pkg.stack; importer != nil {
1182 sumErr.importer = importer.path
1183 sumErr.importerVersion = importer.mod.Version
1184 sumErr.importerIsTest = importer.testOf != nil
1188 if stdErr := (*ImportMissingError)(nil); errors.As(pkg.err, &stdErr) && stdErr.isStd {
1189 // Add importer go version information to import errors of standard
1190 // library packages arising from newer releases.
1191 if importer := pkg.stack; importer != nil {
1192 if v, ok := rawGoVersion.Load(importer.mod); ok && versionLess(LatestGoVersion(), v.(string)) {
1193 stdErr.importerGoVersion = v.(string)
1196 if ld.SilenceMissingStdImports {
1200 if ld.SilencePackageErrors {
1203 if ld.SilenceNoGoErrors && errors.Is(pkg.err, imports.ErrNoGo) {
1207 ld.errorf("%s: %v\n", pkg.stackText(), pkg.err)
1210 ld.checkMultiplePaths()
1214 // versionLess returns whether a < b according to semantic version precedence.
1215 // Both strings are interpreted as go version strings, e.g. "1.19".
1216 func versionLess(a, b string) bool {
1217 return semver.Compare("v"+a, "v"+b) < 0
1220 // updateRequirements ensures that ld.requirements is consistent with the
1221 // information gained from ld.pkgs.
1225 // - Modules that provide packages directly imported from the main module are
1226 // marked as direct, and are promoted to explicit roots. If a needed root
1227 // cannot be promoted due to -mod=readonly or -mod=vendor, the importing
1228 // package is marked with an error.
1230 // - If ld scanned the "all" pattern independent of build constraints, it is
1231 // guaranteed to have seen every direct import. Module dependencies that did
1232 // not provide any directly-imported package are then marked as indirect.
1234 // - Root dependencies are updated to their selected versions.
1236 // The "changed" return value reports whether the update changed the selected
1237 // version of any module that either provided a loaded package or may now
1238 // provide a package that was previously unresolved.
1239 func (ld *loader) updateRequirements(ctx context.Context) (changed bool, err error) {
1240 rs := ld.requirements
1242 // direct contains the set of modules believed to provide packages directly
1243 // imported by the main module.
1244 var direct map[string]bool
1246 // If we didn't scan all of the imports from the main module, or didn't use
1247 // imports.AnyTags, then we didn't necessarily load every package that
1248 // contributes “direct” imports — so we can't safely mark existing direct
1249 // dependencies in ld.requirements as indirect-only. Propagate them as direct.
1250 loadedDirect := ld.allPatternIsRoot && reflect.DeepEqual(ld.Tags, imports.AnyTags())
1252 direct = make(map[string]bool)
1254 // TODO(bcmills): It seems like a shame to allocate and copy a map here when
1255 // it will only rarely actually vary from rs.direct. Measure this cost and
1256 // maybe avoid the copy.
1257 direct = make(map[string]bool, len(rs.direct))
1258 for mPath := range rs.direct {
1259 direct[mPath] = true
1263 for _, pkg := range ld.pkgs {
1264 if pkg.mod.Version != "" || !MainModules.Contains(pkg.mod.Path) {
1267 for _, dep := range pkg.imports {
1268 if !dep.fromExternalModule() {
1272 if inWorkspaceMode() {
1273 // In workspace mode / workspace pruning mode, the roots are the main modules
1274 // rather than the main module's direct dependencies. The check below on the selected
1275 // roots does not apply.
1276 if mg, err := rs.Graph(ctx); err != nil {
1278 } else if _, ok := mg.RequiredBy(dep.mod); !ok {
1279 // dep.mod is not an explicit dependency, but needs to be.
1280 // See comment on error returned below.
1281 pkg.err = &DirectImportFromImplicitDependencyError{
1282 ImporterPath: pkg.path,
1283 ImportedPath: dep.path,
1290 if pkg.err == nil && cfg.BuildMod != "mod" {
1291 if v, ok := rs.rootSelected(dep.mod.Path); !ok || v != dep.mod.Version {
1292 // dep.mod is not an explicit dependency, but needs to be.
1293 // Because we are not in "mod" mode, we will not be able to update it.
1294 // Instead, mark the importing package with an error.
1296 // TODO(#41688): The resulting error message fails to include the file
1297 // position of the import statement (because that information is not
1298 // tracked by the module loader). Figure out how to plumb the import
1299 // position through.
1300 pkg.err = &DirectImportFromImplicitDependencyError{
1301 ImporterPath: pkg.path,
1302 ImportedPath: dep.path,
1305 // cfg.BuildMod does not allow us to change dep.mod to be a direct
1306 // dependency, so don't mark it as such.
1311 // dep is a package directly imported by a package or test in the main
1312 // module and loaded from some other module (not the standard library).
1313 // Mark its module as a direct dependency.
1314 direct[dep.mod.Path] = true
1318 var addRoots []module.Version
1320 // When we are tidying a module with a pruned dependency graph, we may need
1321 // to add roots to preserve the versions of indirect, test-only dependencies
1322 // that are upgraded above or otherwise missing from the go.mod files of
1323 // direct dependencies. (For example, the direct dependency might be a very
1324 // stable codebase that predates modules and thus lacks a go.mod file, or
1325 // the author of the direct dependency may have forgotten to commit a change
1326 // to the go.mod file, or may have made an erroneous hand-edit that causes
1327 // it to be untidy.)
1329 // Promoting an indirect dependency to a root adds the next layer of its
1330 // dependencies to the module graph, which may increase the selected
1331 // versions of other modules from which we have already loaded packages.
1332 // So after we promote an indirect dependency to a root, we need to reload
1333 // packages, which means another iteration of loading.
1335 // As an extra wrinkle, the upgrades due to promoting a root can cause
1336 // previously-resolved packages to become unresolved. For example, the
1337 // module providing an unstable package might be upgraded to a version
1338 // that no longer contains that package. If we then resolve the missing
1339 // package, we might add yet another root that upgrades away some other
1340 // dependency. (The tests in mod_tidy_convergence*.txt illustrate some
1341 // particularly worrisome cases.)
1343 // To ensure that this process of promoting, adding, and upgrading roots
1344 // eventually terminates, during iteration we only ever add modules to the
1345 // root set — we only remove irrelevant roots at the very end of
1346 // iteration, after we have already added every root that we plan to need
1347 // in the (eventual) tidy root set.
1349 // Since we do not remove any roots during iteration, even if they no
1350 // longer provide any imported packages, the selected versions of the
1351 // roots can only increase and the set of roots can only expand. The set
1352 // of extant root paths is finite and the set of versions of each path is
1353 // finite, so the iteration *must* reach a stable fixed-point.
1354 tidy, err := tidyRoots(ctx, rs, ld.pkgs)
1358 addRoots = tidy.rootModules
1361 rs, err = updateRoots(ctx, direct, rs, ld.pkgs, addRoots, ld.AssumeRootsImported)
1363 // We don't actually know what even the root requirements are supposed to be,
1364 // so we can't proceed with loading. Return the error to the caller
1368 if rs != ld.requirements && !reflect.DeepEqual(rs.rootModules, ld.requirements.rootModules) {
1369 // The roots of the module graph have changed in some way (not just the
1370 // "direct" markings). Check whether the changes affected any of the loaded
1372 mg, err := rs.Graph(ctx)
1376 for _, pkg := range ld.pkgs {
1377 if pkg.fromExternalModule() && mg.Selected(pkg.mod.Path) != pkg.mod.Version {
1382 // Promoting a module to a root may resolve an import that was
1383 // previously missing (by pulling in a previously-prune dependency that
1384 // provides it) or ambiguous (by promoting exactly one of the
1385 // alternatives to a root and ignoring the second-level alternatives) or
1386 // otherwise errored out (by upgrading from a version that cannot be
1387 // fetched to one that can be).
1389 // Instead of enumerating all of the possible errors, we'll just check
1390 // whether importFromModules returns nil for the package.
1391 // False-positives are ok: if we have a false-positive here, we'll do an
1392 // extra iteration of package loading this time, but we'll still
1393 // converge when the root set stops changing.
1395 // In some sense, we can think of this as ‘upgraded the module providing
1396 // pkg.path from "none" to a version higher than "none"’.
1397 if _, _, _, _, err = importFromModules(ctx, pkg.path, rs, nil); err == nil {
1405 ld.requirements = rs
1409 // resolveMissingImports returns a set of modules that could be added as
1410 // dependencies in order to resolve missing packages from pkgs.
1412 // The newly-resolved packages are added to the addedModuleFor map, and
1413 // resolveMissingImports returns a map from each new module version to
1414 // the first missing package that module would resolve.
1415 func (ld *loader) resolveMissingImports(ctx context.Context) (modAddedBy map[module.Version]*loadPkg) {
1416 type pkgMod struct {
1420 var pkgMods []pkgMod
1421 for _, pkg := range ld.pkgs {
1426 // If we are missing a test, we are also missing its non-test version, and
1427 // we should only add the missing import once.
1430 if !errors.As(pkg.err, new(*ImportMissingError)) {
1431 // Leave other errors for Import or load.Packages to report.
1436 var mod module.Version
1437 ld.work.Add(func() {
1439 mod, err = queryImport(ctx, pkg.path, ld.requirements)
1441 var ime *ImportMissingError
1442 if errors.As(err, &ime) {
1443 for curstack := pkg.stack; curstack != nil; curstack = curstack.stack {
1444 if MainModules.Contains(curstack.mod.Path) {
1445 ime.ImportingMainModule = curstack.mod
1450 // pkg.err was already non-nil, so we can reasonably attribute the error
1451 // for pkg to either the original error or the one returned by
1452 // queryImport. The existing error indicates only that we couldn't find
1453 // the package, whereas the query error also explains why we didn't fix
1454 // the problem — so we prefer the latter.
1458 // err is nil, but we intentionally leave pkg.err non-nil and pkg.mod
1459 // unset: we still haven't satisfied other invariants of a
1460 // successfully-loaded package, such as scanning and loading the imports
1461 // of that package. If we succeed in resolving the new dependency graph,
1462 // the caller can reload pkg and update the error at that point.
1464 // Even then, the package might not be loaded from the version we've
1465 // identified here. The module may be upgraded by some other dependency,
1466 // or by a transitive dependency of mod itself, or — less likely — the
1467 // package may be rejected by an AllowPackage hook or rendered ambiguous
1468 // by some other newly-added or newly-upgraded dependency.
1471 pkgMods = append(pkgMods, pkgMod{pkg: pkg, mod: &mod})
1475 modAddedBy = map[module.Version]*loadPkg{}
1476 for _, pm := range pkgMods {
1477 pkg, mod := pm.pkg, *pm.mod
1482 fmt.Fprintf(os.Stderr, "go: found %s in %s %s\n", pkg.path, mod.Path, mod.Version)
1483 if modAddedBy[mod] == nil {
1484 modAddedBy[mod] = pkg
1491 // pkg locates the *loadPkg for path, creating and queuing it for loading if
1492 // needed, and updates its state to reflect the given flags.
1494 // The imports of the returned *loadPkg will be loaded asynchronously in the
1495 // ld.work queue, and its test (if requested) will also be populated once
1496 // imports have been resolved. When ld.work goes idle, all transitive imports of
1497 // the requested package (and its test, if requested) will have been loaded.
1498 func (ld *loader) pkg(ctx context.Context, path string, flags loadPkgFlags) *loadPkg {
1499 if flags.has(pkgImportsLoaded) {
1500 panic("internal error: (*loader).pkg called with pkgImportsLoaded flag set")
1503 pkg := ld.pkgCache.Do(path, func() any {
1507 ld.applyPkgFlags(ctx, pkg, flags)
1509 ld.work.Add(func() { ld.load(ctx, pkg) })
1513 ld.applyPkgFlags(ctx, pkg, flags)
1517 // applyPkgFlags updates pkg.flags to set the given flags and propagate the
1518 // (transitive) effects of those flags, possibly loading or enqueueing further
1519 // packages as a result.
1520 func (ld *loader) applyPkgFlags(ctx context.Context, pkg *loadPkg, flags loadPkgFlags) {
1525 if flags.has(pkgInAll) && ld.allPatternIsRoot && !pkg.isTest() {
1526 // This package matches a root pattern by virtue of being in "all".
1529 if flags.has(pkgIsRoot) {
1530 flags |= pkgFromRoot
1533 old := pkg.flags.update(flags)
1535 if new == old || !new.has(pkgImportsLoaded) {
1536 // We either didn't change the state of pkg, or we don't know anything about
1537 // its dependencies yet. Either way, we can't usefully load its test or
1538 // update its dependencies.
1543 // Check whether we should add (or update the flags for) a test for pkg.
1544 // ld.pkgTest is idempotent and extra invocations are inexpensive,
1545 // so it's ok if we call it more than is strictly necessary.
1548 case ld.allPatternIsRoot && MainModules.Contains(pkg.mod.Path):
1549 // We are loading the "all" pattern, which includes packages imported by
1550 // tests in the main module. This package is in the main module, so we
1551 // need to identify the imports of its test even if LoadTests is not set.
1553 // (We will filter out the extra tests explicitly in computePatternAll.)
1556 case ld.allPatternIsRoot && ld.allClosesOverTests && new.has(pkgInAll):
1557 // This variant of the "all" pattern includes imports of tests of every
1558 // package that is itself in "all", and pkg is in "all", so its test is
1559 // also in "all" (as above).
1562 case ld.LoadTests && new.has(pkgIsRoot):
1563 // LoadTest explicitly requests tests of “the root packages”.
1568 var testFlags loadPkgFlags
1569 if MainModules.Contains(pkg.mod.Path) || (ld.allClosesOverTests && new.has(pkgInAll)) {
1570 // Tests of packages in the main module are in "all", in the sense that
1571 // they cause the packages they import to also be in "all". So are tests
1572 // of packages in "all" if "all" closes over test dependencies.
1573 testFlags |= pkgInAll
1575 ld.pkgTest(ctx, pkg, testFlags)
1579 if new.has(pkgInAll) && !old.has(pkgInAll|pkgImportsLoaded) {
1580 // We have just marked pkg with pkgInAll, or we have just loaded its
1581 // imports, or both. Now is the time to propagate pkgInAll to the imports.
1582 for _, dep := range pkg.imports {
1583 ld.applyPkgFlags(ctx, dep, pkgInAll)
1587 if new.has(pkgFromRoot) && !old.has(pkgFromRoot|pkgImportsLoaded) {
1588 for _, dep := range pkg.imports {
1589 ld.applyPkgFlags(ctx, dep, pkgFromRoot)
1594 // preloadRootModules loads the module requirements needed to identify the
1595 // selected version of each module providing a package in rootPkgs,
1596 // adding new root modules to the module graph if needed.
1597 func (ld *loader) preloadRootModules(ctx context.Context, rootPkgs []string) (changedBuildList bool) {
1598 needc := make(chan map[module.Version]bool, 1)
1599 needc <- map[module.Version]bool{}
1600 for _, path := range rootPkgs {
1602 ld.work.Add(func() {
1603 // First, try to identify the module containing the package using only roots.
1605 // If the main module is tidy and the package is in "all" — or if we're
1606 // lucky — we can identify all of its imports without actually loading the
1607 // full module graph.
1608 m, _, _, _, err := importFromModules(ctx, path, ld.requirements, nil)
1610 var missing *ImportMissingError
1611 if errors.As(err, &missing) && ld.ResolveMissingImports {
1612 // This package isn't provided by any selected module.
1613 // If we can find it, it will be a new root dependency.
1614 m, err = queryImport(ctx, path, ld.requirements)
1617 // We couldn't identify the root module containing this package.
1618 // Leave it unresolved; we will report it during loading.
1623 // The package is in std or cmd. We don't need to change the root set.
1627 v, ok := ld.requirements.rootSelected(m.Path)
1628 if !ok || v != m.Version {
1629 // We found the requested package in m, but m is not a root, so
1630 // loadModGraph will not load its requirements. We need to promote the
1631 // module to a root to ensure that any other packages this package
1632 // imports are resolved from correct dependency versions.
1634 // (This is the “argument invariant” from
1635 // https://golang.org/design/36460-lazy-module-loading.)
1646 return false // No roots to add.
1649 toAdd := make([]module.Version, 0, len(need))
1650 for m := range need {
1651 toAdd = append(toAdd, m)
1655 rs, err := updateRoots(ctx, ld.requirements.direct, ld.requirements, nil, toAdd, ld.AssumeRootsImported)
1657 // We are missing some root dependency, and for some reason we can't load
1658 // enough of the module dependency graph to add the missing root. Package
1659 // loading is doomed to fail, so fail quickly.
1660 ld.errorf("go: %v\n", err)
1664 if reflect.DeepEqual(rs.rootModules, ld.requirements.rootModules) {
1665 // Something is deeply wrong. resolveMissingImports gave us a non-empty
1666 // set of modules to add to the graph, but adding those modules had no
1667 // effect — either they were already in the graph, or updateRoots did not
1668 // add them as requested.
1669 panic(fmt.Sprintf("internal error: adding %v to module graph had no effect on root requirements (%v)", toAdd, rs.rootModules))
1672 ld.requirements = rs
1676 // load loads an individual package.
1677 func (ld *loader) load(ctx context.Context, pkg *loadPkg) {
1679 if ld.requirements.pruning == unpruned {
1681 mg, err = ld.requirements.Graph(ctx)
1683 // We already checked the error from Graph in loadFromRoots and/or
1684 // updateRequirements, so we ignored the error on purpose and we should
1685 // keep trying to push past it.
1687 // However, because mg may be incomplete (and thus may select inaccurate
1688 // versions), we shouldn't use it to load packages. Instead, we pass a nil
1689 // *ModuleGraph, which will cause mg to first try loading from only the
1690 // main module and root dependencies.
1696 pkg.mod, modroot, pkg.dir, pkg.altMods, pkg.err = importFromModules(ctx, pkg.path, ld.requirements, mg)
1700 if MainModules.Contains(pkg.mod.Path) {
1701 // Go ahead and mark pkg as in "all". This provides the invariant that a
1702 // package that is *only* imported by other packages in "all" is always
1703 // marked as such before loading its imports.
1705 // We don't actually rely on that invariant at the moment, but it may
1706 // improve efficiency somewhat and makes the behavior a bit easier to reason
1707 // about (by reducing churn on the flag bits of dependencies), and costs
1708 // essentially nothing (these atomic flag ops are essentially free compared
1709 // to scanning source code for imports).
1710 ld.applyPkgFlags(ctx, pkg, pkgInAll)
1712 if ld.AllowPackage != nil {
1713 if err := ld.AllowPackage(ctx, pkg.path, pkg.mod); err != nil {
1718 pkg.inStd = (search.IsStandardImportPath(pkg.path) && search.InDir(pkg.dir, cfg.GOROOTsrc) != "")
1720 var imports, testImports []string
1722 if cfg.BuildContext.Compiler == "gccgo" && pkg.inStd {
1723 // We can't scan standard packages for gccgo.
1726 imports, testImports, err = scanDir(modroot, pkg.dir, ld.Tags)
1733 pkg.imports = make([]*loadPkg, 0, len(imports))
1734 var importFlags loadPkgFlags
1735 if pkg.flags.has(pkgInAll) {
1736 importFlags = pkgInAll
1738 for _, path := range imports {
1740 // Imports from packages in "std" and "cmd" should resolve using
1741 // GOROOT/src/vendor even when "std" is not the main module.
1742 path = ld.stdVendor(pkg.path, path)
1744 pkg.imports = append(pkg.imports, ld.pkg(ctx, path, importFlags))
1746 pkg.testImports = testImports
1748 ld.applyPkgFlags(ctx, pkg, pkgImportsLoaded)
1751 // pkgTest locates the test of pkg, creating it if needed, and updates its state
1752 // to reflect the given flags.
1754 // pkgTest requires that the imports of pkg have already been loaded (flagged
1755 // with pkgImportsLoaded).
1756 func (ld *loader) pkgTest(ctx context.Context, pkg *loadPkg, testFlags loadPkgFlags) *loadPkg {
1758 panic("pkgTest called on a test package")
1761 createdTest := false
1762 pkg.testOnce.Do(func() {
1763 pkg.test = &loadPkg{
1771 ld.applyPkgFlags(ctx, pkg.test, testFlags)
1777 test.imports = make([]*loadPkg, 0, len(pkg.testImports))
1778 var importFlags loadPkgFlags
1779 if test.flags.has(pkgInAll) {
1780 importFlags = pkgInAll
1782 for _, path := range pkg.testImports {
1784 path = ld.stdVendor(test.path, path)
1786 test.imports = append(test.imports, ld.pkg(ctx, path, importFlags))
1788 pkg.testImports = nil
1789 ld.applyPkgFlags(ctx, test, pkgImportsLoaded)
1791 ld.applyPkgFlags(ctx, test, testFlags)
1797 // stdVendor returns the canonical import path for the package with the given
1798 // path when imported from the standard-library package at parentPath.
1799 func (ld *loader) stdVendor(parentPath, path string) string {
1800 if search.IsStandardImportPath(path) {
1804 if str.HasPathPrefix(parentPath, "cmd") {
1805 if !ld.VendorModulesInGOROOTSrc || !MainModules.Contains("cmd") {
1806 vendorPath := pathpkg.Join("cmd", "vendor", path)
1808 if _, err := os.Stat(filepath.Join(cfg.GOROOTsrc, filepath.FromSlash(vendorPath))); err == nil {
1812 } else if !ld.VendorModulesInGOROOTSrc || !MainModules.Contains("std") || str.HasPathPrefix(parentPath, "vendor") {
1813 // If we are outside of the 'std' module, resolve imports from within 'std'
1814 // to the vendor directory.
1816 // Do the same for importers beginning with the prefix 'vendor/' even if we
1817 // are *inside* of the 'std' module: the 'vendor/' packages that resolve
1818 // globally from GOROOT/src/vendor (and are listed as part of 'go list std')
1819 // are distinct from the real module dependencies, and cannot import
1820 // internal packages from the real module.
1822 // (Note that although the 'vendor/' packages match the 'std' *package*
1823 // pattern, they are not part of the std *module*, and do not affect
1824 // 'go mod tidy' and similar module commands when working within std.)
1825 vendorPath := pathpkg.Join("vendor", path)
1826 if _, err := os.Stat(filepath.Join(cfg.GOROOTsrc, filepath.FromSlash(vendorPath))); err == nil {
1831 // Not vendored: resolve from modules.
1835 // computePatternAll returns the list of packages matching pattern "all",
1836 // starting with a list of the import paths for the packages in the main module.
1837 func (ld *loader) computePatternAll() (all []string) {
1838 for _, pkg := range ld.pkgs {
1839 if pkg.flags.has(pkgInAll) && !pkg.isTest() {
1840 all = append(all, pkg.path)
1847 // checkMultiplePaths verifies that a given module path is used as itself
1848 // or as a replacement for another module, but not both at the same time.
1850 // (See https://golang.org/issue/26607 and https://golang.org/issue/34650.)
1851 func (ld *loader) checkMultiplePaths() {
1852 mods := ld.requirements.rootModules
1853 if cached := ld.requirements.graph.Load(); cached != nil {
1854 if mg := cached.mg; mg != nil {
1855 mods = mg.BuildList()
1859 firstPath := map[module.Version]string{}
1860 for _, mod := range mods {
1861 src := resolveReplacement(mod)
1862 if prev, ok := firstPath[src]; !ok {
1863 firstPath[src] = mod.Path
1864 } else if prev != mod.Path {
1865 ld.errorf("go: %s@%s used for two different module paths (%s and %s)\n", src.Path, src.Version, prev, mod.Path)
1870 // checkTidyCompatibility emits an error if any package would be loaded from a
1871 // different module under rs than under ld.requirements.
1872 func (ld *loader) checkTidyCompatibility(ctx context.Context, rs *Requirements) {
1873 suggestUpgrade := false
1874 suggestEFlag := false
1875 suggestFixes := func() {
1877 // The user is explicitly ignoring these errors, so don't bother them with
1882 // We print directly to os.Stderr because this information is advice about
1883 // how to fix errors, not actually an error itself.
1884 // (The actual errors should have been logged already.)
1886 fmt.Fprintln(os.Stderr)
1889 if ld.GoVersion != MainModules.GoVersion() {
1890 goFlag = " -go=" + ld.GoVersion
1894 if ld.TidyCompatibleVersion != priorGoVersion(ld.GoVersion) {
1895 compatFlag = " -compat=" + ld.TidyCompatibleVersion
1901 eDesc = ", leaving some packages unresolved"
1904 fmt.Fprintf(os.Stderr, "To upgrade to the versions selected by go %s%s:\n\tgo mod tidy%s -go=%s && go mod tidy%s -go=%s%s\n", ld.TidyCompatibleVersion, eDesc, eFlag, ld.TidyCompatibleVersion, eFlag, ld.GoVersion, compatFlag)
1905 } else if suggestEFlag {
1906 // If some packages are missing but no package is upgraded, then we
1907 // shouldn't suggest upgrading to the Go 1.16 versions explicitly — that
1908 // wouldn't actually fix anything for Go 1.16 users, and *would* break
1909 // something for Go 1.17 users.
1910 fmt.Fprintf(os.Stderr, "To proceed despite packages unresolved in go %s:\n\tgo mod tidy -e%s%s\n", ld.TidyCompatibleVersion, goFlag, compatFlag)
1913 fmt.Fprintf(os.Stderr, "If reproducibility with go %s is not needed:\n\tgo mod tidy%s -compat=%s\n", ld.TidyCompatibleVersion, goFlag, ld.GoVersion)
1915 // TODO(#46141): Populate the linked wiki page.
1916 fmt.Fprintf(os.Stderr, "For other options, see:\n\thttps://golang.org/doc/modules/pruning\n")
1919 mg, err := rs.Graph(ctx)
1921 ld.errorf("go: error loading go %s module graph: %v\n", ld.TidyCompatibleVersion, err)
1926 // Re-resolve packages in parallel.
1928 // We re-resolve each package — rather than just checking versions — to ensure
1929 // that we have fetched module source code (and, importantly, checksums for
1930 // that source code) for all modules that are necessary to ensure that imports
1931 // are unambiguous. That also produces clearer diagnostics, since we can say
1932 // exactly what happened to the package if it became ambiguous or disappeared
1935 // We re-resolve the packages in parallel because this process involves disk
1936 // I/O to check for package sources, and because the process of checking for
1937 // ambiguous imports may require us to download additional modules that are
1938 // otherwise pruned out in Go 1.17 — we don't want to block progress on other
1939 // packages while we wait for a single new download.
1940 type mismatch struct {
1944 mismatchMu := make(chan map[*loadPkg]mismatch, 1)
1945 mismatchMu <- map[*loadPkg]mismatch{}
1946 for _, pkg := range ld.pkgs {
1947 if pkg.mod.Path == "" && pkg.err == nil {
1948 // This package is from the standard library (which does not vary based on
1949 // the module graph).
1954 ld.work.Add(func() {
1955 mod, _, _, _, err := importFromModules(ctx, pkg.path, rs, mg)
1957 mismatches := <-mismatchMu
1958 mismatches[pkg] = mismatch{mod: mod, err: err}
1959 mismatchMu <- mismatches
1965 mismatches := <-mismatchMu
1966 if len(mismatches) == 0 {
1967 // Since we're running as part of 'go mod tidy', the roots of the module
1968 // graph should contain only modules that are relevant to some package in
1969 // the package graph. We checked every package in the package graph and
1970 // didn't find any mismatches, so that must mean that all of the roots of
1971 // the module graph are also consistent.
1973 // If we're wrong, Go 1.16 in -mod=readonly mode will error out with
1974 // "updates to go.mod needed", which would be very confusing. So instead,
1975 // we'll double-check that our reasoning above actually holds — if it
1976 // doesn't, we'll emit an internal error and hopefully the user will report
1978 for _, m := range ld.requirements.rootModules {
1979 if v := mg.Selected(m.Path); v != m.Version {
1980 fmt.Fprintln(os.Stderr)
1981 base.Fatalf("go: internal error: failed to diagnose selected-version mismatch for module %s: go %s selects %s, but go %s selects %s\n\tPlease report this at https://golang.org/issue.", m.Path, ld.GoVersion, m.Version, ld.TidyCompatibleVersion, v)
1987 // Iterate over the packages (instead of the mismatches map) to emit errors in
1988 // deterministic order.
1989 for _, pkg := range ld.pkgs {
1990 mismatch, ok := mismatches[pkg]
1996 // We already did (or will) report an error for the package itself,
1997 // so don't report a duplicate (and more vebose) error for its test.
1998 if _, ok := mismatches[pkg.testOf]; !ok {
1999 base.Fatalf("go: internal error: mismatch recorded for test %s, but not its non-test package", pkg.path)
2005 case mismatch.err != nil:
2006 // pkg resolved successfully, but errors out using the requirements in rs.
2008 // This could occur because the import is provided by a single root (and
2009 // is thus unambiguous in a main module with a pruned module graph) and
2010 // also one or more transitive dependencies (and is ambiguous with an
2013 // It could also occur because some transitive dependency upgrades the
2014 // module that previously provided the package to a version that no
2015 // longer does, or to a version for which the module source code (but
2016 // not the go.mod file in isolation) has a checksum error.
2017 if missing := (*ImportMissingError)(nil); errors.As(mismatch.err, &missing) {
2018 selected := module.Version{
2020 Version: mg.Selected(pkg.mod.Path),
2022 ld.errorf("%s loaded from %v,\n\tbut go %s would fail to locate it in %s\n", pkg.stackText(), pkg.mod, ld.TidyCompatibleVersion, selected)
2024 if ambiguous := (*AmbiguousImportError)(nil); errors.As(mismatch.err, &ambiguous) {
2025 // TODO: Is this check needed?
2027 ld.errorf("%s loaded from %v,\n\tbut go %s would fail to locate it:\n\t%v\n", pkg.stackText(), pkg.mod, ld.TidyCompatibleVersion, mismatch.err)
2032 // Even if we press ahead with the '-e' flag, the older version will
2033 // error out in readonly mode if it thinks the go.mod file contains
2034 // any *explicit* dependency that is not at its selected version,
2035 // even if that dependency is not relevant to any package being loaded.
2037 // We check for that condition here. If all of the roots are consistent
2038 // the '-e' flag suffices, but otherwise we need to suggest an upgrade.
2039 if !suggestUpgrade {
2040 for _, m := range ld.requirements.rootModules {
2041 if v := mg.Selected(m.Path); v != m.Version {
2042 suggestUpgrade = true
2048 case pkg.err != nil:
2049 // pkg had an error in with a pruned module graph (presumably suppressed
2050 // with the -e flag), but the error went away using an unpruned graph.
2052 // This is possible, if, say, the import is unresolved in the pruned graph
2053 // (because the "latest" version of each candidate module either is
2054 // unavailable or does not contain the package), but is resolved in the
2055 // unpruned graph due to a newer-than-latest dependency that is normally
2058 // This could also occur if the source code for the module providing the
2059 // package in the pruned graph has a checksum error, but the unpruned
2060 // graph upgrades that module to a version with a correct checksum.
2062 // pkg.err should have already been logged elsewhere — along with a
2063 // stack trace — so log only the import path and non-error info here.
2064 suggestUpgrade = true
2065 ld.errorf("%s failed to load from any module,\n\tbut go %s would load it from %v\n", pkg.path, ld.TidyCompatibleVersion, mismatch.mod)
2067 case pkg.mod != mismatch.mod:
2068 // The package is loaded successfully by both Go versions, but from a
2069 // different module in each. This could lead to subtle (and perhaps even
2070 // unnoticed!) variations in behavior between builds with different
2072 suggestUpgrade = true
2073 ld.errorf("%s loaded from %v,\n\tbut go %s would select %v\n", pkg.stackText(), pkg.mod, ld.TidyCompatibleVersion, mismatch.mod.Version)
2076 base.Fatalf("go: internal error: mismatch recorded for package %s, but no differences found", pkg.path)
2084 // scanDir is like imports.ScanDir but elides known magic imports from the list,
2085 // so that we do not go looking for packages that don't really exist.
2087 // The standard magic import is "C", for cgo.
2089 // The only other known magic imports are appengine and appengine/*.
2090 // These are so old that they predate "go get" and did not use URL-like paths.
2091 // Most code today now uses google.golang.org/appengine instead,
2092 // but not all code has been so updated. When we mostly ignore build tags
2093 // during "go vendor", we look into "// +build appengine" files and
2094 // may see these legacy imports. We drop them so that the module
2095 // search does not look for modules to try to satisfy them.
2096 func scanDir(modroot string, dir string, tags map[string]bool) (imports_, testImports []string, err error) {
2097 if ip, mierr := modindex.GetPackage(modroot, dir); mierr == nil {
2098 imports_, testImports, err = ip.ScanDir(tags)
2100 } else if !errors.Is(mierr, modindex.ErrNotIndexed) {
2101 return nil, nil, mierr
2104 imports_, testImports, err = imports.ScanDir(dir, tags)
2107 filter := func(x []string) []string {
2109 for _, pkg := range x {
2110 if pkg != "C" && pkg != "appengine" && !strings.HasPrefix(pkg, "appengine/") &&
2111 pkg != "appengine_internal" && !strings.HasPrefix(pkg, "appengine_internal/") {
2119 return filter(imports_), filter(testImports), err
2122 // buildStacks computes minimal import stacks for each package,
2123 // for use in error messages. When it completes, packages that
2124 // are part of the original root set have pkg.stack == nil,
2125 // and other packages have pkg.stack pointing at the next
2126 // package up the import stack in their minimal chain.
2127 // As a side effect, buildStacks also constructs ld.pkgs,
2128 // the list of all packages loaded.
2129 func (ld *loader) buildStacks() {
2130 if len(ld.pkgs) > 0 {
2131 panic("buildStacks")
2133 for _, pkg := range ld.roots {
2134 pkg.stack = pkg // sentinel to avoid processing in next loop
2135 ld.pkgs = append(ld.pkgs, pkg)
2137 for i := 0; i < len(ld.pkgs); i++ { // not range: appending to ld.pkgs in loop
2139 for _, next := range pkg.imports {
2140 if next.stack == nil {
2142 ld.pkgs = append(ld.pkgs, next)
2145 if next := pkg.test; next != nil && next.stack == nil {
2147 ld.pkgs = append(ld.pkgs, next)
2150 for _, pkg := range ld.roots {
2155 // stackText builds the import stack text to use when
2156 // reporting an error in pkg. It has the general form
2161 // other2.test imports
2163 func (pkg *loadPkg) stackText() string {
2164 var stack []*loadPkg
2165 for p := pkg; p != nil; p = p.stack {
2166 stack = append(stack, p)
2169 var buf strings.Builder
2170 for i := len(stack) - 1; i >= 0; i-- {
2172 fmt.Fprint(&buf, p.path)
2173 if p.testOf != nil {
2174 fmt.Fprint(&buf, ".test")
2177 if stack[i-1].testOf == p {
2178 fmt.Fprint(&buf, " tested by\n\t")
2180 fmt.Fprint(&buf, " imports\n\t")
2187 // why returns the text to use in "go mod why" output about the given package.
2188 // It is less ornate than the stackText but contains the same information.
2189 func (pkg *loadPkg) why() string {
2190 var buf strings.Builder
2191 var stack []*loadPkg
2192 for p := pkg; p != nil; p = p.stack {
2193 stack = append(stack, p)
2196 for i := len(stack) - 1; i >= 0; i-- {
2198 if p.testOf != nil {
2199 fmt.Fprintf(&buf, "%s.test\n", p.testOf.path)
2201 fmt.Fprintf(&buf, "%s\n", p.path)
2207 // Why returns the "go mod why" output stanza for the given package,
2208 // without the leading # comment.
2209 // The package graph must have been loaded already, usually by LoadPackages.
2210 // If there is no reason for the package to be in the current build,
2211 // Why returns an empty string.
2212 func Why(path string) string {
2213 pkg, ok := loaded.pkgCache.Get(path).(*loadPkg)
2220 // WhyDepth returns the number of steps in the Why listing.
2221 // If there is no reason for the package to be in the current build,
2222 // WhyDepth returns 0.
2223 func WhyDepth(path string) int {
2225 pkg, _ := loaded.pkgCache.Get(path).(*loadPkg)
2226 for p := pkg; p != nil; p = p.stack {