go/packages/golist_overlay.go - tools - Git at Google

 package packages

 import (
 	"encoding/json"
 	"fmt"
 	"go/parser"
 	"go/token"
 	"os"
 	"path/filepath"
 	"sort"
 	"strconv"
 	"strings"
 )

 // processGolistOverlay provides rudimentary support for adding
 // files that don't exist on disk to an overlay. The results can be
 // sometimes incorrect.
 // TODO(matloob): Handle unsupported cases, including the following:
 // - determining the correct package to add given a new import path
 func (state *golistState) processGolistOverlay(response *responseDeduper) (modifiedPkgs, needPkgs []string, err error) {
 	havePkgs := make(map[string]string) // importPath -> non-test package ID
 	needPkgsSet := make(map[string]bool)
 	modifiedPkgsSet := make(map[string]bool)

 	for _, pkg := range response.dr.Packages {
 		// This is an approximation of import path to id. This can be
 		// wrong for tests, vendored packages, and a number of other cases.
 		havePkgs[pkg.PkgPath] = pkg.ID
 	}

 	// If no new imports are added, it is safe to avoid loading any needPkgs.
 	// Otherwise, it's hard to tell which package is actually being loaded
 	// (due to vendoring) and whether any modified package will show up
 	// in the transitive set of dependencies (because new imports are added,
 	// potentially modifying the transitive set of dependencies).
 	var overlayAddsImports bool

 	// If both a package and its test package are created by the overlay, we
 	// need the real package first. Process all non-test files before test
 	// files, and make the whole process deterministic while we're at it.
 	var overlayFiles []string
 	for opath := range state.cfg.Overlay {
 		overlayFiles = append(overlayFiles, opath)
 	}
 	sort.Slice(overlayFiles, func(i, j int) bool {
 		iTest := strings.HasSuffix(overlayFiles[i], "_test.go")
 		jTest := strings.HasSuffix(overlayFiles[j], "_test.go")
 		if iTest != jTest {
 			return !iTest // non-tests are before tests.
 		}
 		return overlayFiles[i] < overlayFiles[j]
 	})
 	for _, opath := range overlayFiles {
 		contents := state.cfg.Overlay[opath]
 		base := filepath.Base(opath)
 		dir := filepath.Dir(opath)
 		var pkg *Package           // if opath belongs to both a package and its test variant, this will be the test variant
 		var testVariantOf *Package // if opath is a test file, this is the package it is testing
 		var fileExists bool
 		isTestFile := strings.HasSuffix(opath, "_test.go")
 		pkgName, ok := extractPackageName(opath, contents)
 		if !ok {
 			// Don't bother adding a file that doesn't even have a parsable package statement
 			// to the overlay.
 			continue
 		}
 	nextPackage:
 		for _, p := range response.dr.Packages {
 			if pkgName != p.Name && p.ID != "command-line-arguments" {
 				continue
 			}
 			for _, f := range p.GoFiles {
 				if !sameFile(filepath.Dir(f), dir) {
 					continue
 				}
 				// Make sure to capture information on the package's test variant, if needed.
 				if isTestFile && !hasTestFiles(p) {
 					// TODO(matloob): Are there packages other than the 'production' variant
 					// of a package that this can match? This shouldn't match the test main package
 					// because the file is generated in another directory.
 					testVariantOf = p
 					continue nextPackage
 				}
 				// We must have already seen the package of which this is a test variant.
 				if pkg != nil && p != pkg && pkg.PkgPath == p.PkgPath {
 					if hasTestFiles(p) {
 						testVariantOf = pkg
 					}
 				}
 				pkg = p
 				if filepath.Base(f) == base {
 					fileExists = true
 				}
 			}
 		}
 		// The overlay could have included an entirely new package.
 		if pkg == nil {
 			// Try to find the module or gopath dir the file is contained in.
 			// Then for modules, add the module opath to the beginning.
 			pkgPath, ok, err := state.getPkgPath(dir)
 			if err != nil {
 				return nil, nil, err
 			}
 			if !ok {
 				break
 			}
 			isXTest := strings.HasSuffix(pkgName, "_test")
 			if isXTest {
 				pkgPath += "_test"
 			}
 			id := pkgPath
 			if isTestFile && !isXTest {
 				id = fmt.Sprintf("%s [%s.test]", pkgPath, pkgPath)
 			}
 			// Try to reclaim a package with the same id if it exists in the response.
 			for _, p := range response.dr.Packages {
 				if reclaimPackage(p, id, opath, contents) {
 					pkg = p
 					break
 				}
 			}
 			// Otherwise, create a new package
 			if pkg == nil {
 				pkg = &Package{PkgPath: pkgPath, ID: id, Name: pkgName, Imports: make(map[string]*Package)}
 				response.addPackage(pkg)
 				havePkgs[pkg.PkgPath] = id
 				// Add the production package's sources for a test variant.
 				if isTestFile && !isXTest && testVariantOf != nil {
 					pkg.GoFiles = append(pkg.GoFiles, testVariantOf.GoFiles...)
 					pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, testVariantOf.CompiledGoFiles...)
 					// Add the package under test and its imports to the test variant.
 					pkg.forTest = testVariantOf.PkgPath
 					for k, v := range testVariantOf.Imports {
 						pkg.Imports[k] = &Package{ID: v.ID}
 					}
 				}
 			}
 		}
 		if !fileExists {
 			pkg.GoFiles = append(pkg.GoFiles, opath)
 			// TODO(matloob): Adding the file to CompiledGoFiles can exhibit the wrong behavior
 			// if the file will be ignored due to its build tags.
 			pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, opath)
 			modifiedPkgsSet[pkg.ID] = true
 		}
 		imports, err := extractImports(opath, contents)
 		if err != nil {
 			// Let the parser or type checker report errors later.
 			continue
 		}
 		for _, imp := range imports {
 			if _, found := pkg.Imports[imp]; found {
 				continue
 			}
 			overlayAddsImports = true
 			id, ok := havePkgs[imp]
 			if !ok {
 				var err error
 				id, err = state.resolveImport(dir, imp)
 				if err != nil {
 					return nil, nil, err
 				}
 			}
 			pkg.Imports[imp] = &Package{ID: id}
 			// Add dependencies to the non-test variant version of this package as well.
 			if testVariantOf != nil {
 				testVariantOf.Imports[imp] = &Package{ID: id}
 			}
 		}
 	}

 	// toPkgPath guesses the package path given the id.
 	toPkgPath := func(sourceDir, id string) (string, error) {
 		if i := strings.IndexByte(id, ' '); i >= 0 {
 			return state.resolveImport(sourceDir, id[:i])
 		}
 		return state.resolveImport(sourceDir, id)
 	}

 	// Now that new packages have been created, do another pass to determine
 	// the new set of missing packages.
 	for _, pkg := range response.dr.Packages {
 		for _, imp := range pkg.Imports {
 			if len(pkg.GoFiles) == 0 {
 				return nil, nil, fmt.Errorf("cannot resolve imports for package %q with no Go files", pkg.PkgPath)
 			}
 			pkgPath, err := toPkgPath(filepath.Dir(pkg.GoFiles[0]), imp.ID)
 			if err != nil {
 				return nil, nil, err
 			}
 			if _, ok := havePkgs[pkgPath]; !ok {
 				needPkgsSet[pkgPath] = true
 			}
 		}
 	}

 	if overlayAddsImports {
 		needPkgs = make([]string, 0, len(needPkgsSet))
 		for pkg := range needPkgsSet {
 			needPkgs = append(needPkgs, pkg)
 		}
 	}
 	modifiedPkgs = make([]string, 0, len(modifiedPkgsSet))
 	for pkg := range modifiedPkgsSet {
 		modifiedPkgs = append(modifiedPkgs, pkg)
 	}
 	return modifiedPkgs, needPkgs, err
 }

 // resolveImport finds the the ID of a package given its import path.
 // In particular, it will find the right vendored copy when in GOPATH mode.
 func (state *golistState) resolveImport(sourceDir, importPath string) (string, error) {
 	env, err := state.getEnv()
 	if err != nil {
 		return "", err
 	}
 	if env["GOMOD"] != "" {
 		return importPath, nil
 	}

 	searchDir := sourceDir
 	for {
 		vendorDir := filepath.Join(searchDir, "vendor")
 		exists, ok := state.vendorDirs[vendorDir]
 		if !ok {
 			info, err := os.Stat(vendorDir)
 			exists = err == nil && info.IsDir()
 			state.vendorDirs[vendorDir] = exists
 		}

 		if exists {
 			vendoredPath := filepath.Join(vendorDir, importPath)
 			if info, err := os.Stat(vendoredPath); err == nil && info.IsDir() {
 				// We should probably check for .go files here, but shame on anyone who fools us.
 				path, ok, err := state.getPkgPath(vendoredPath)
 				if err != nil {
 					return "", err
 				}
 				if ok {
 					return path, nil
 				}
 			}
 		}

 		// We know we've hit the top of the filesystem when we Dir / and get /,
 		// or C:\ and get C:\, etc.
 		next := filepath.Dir(searchDir)
 		if next == searchDir {
 			break
 		}
 		searchDir = next
 	}
 	return importPath, nil
 }

 func hasTestFiles(p *Package) bool {
 	for _, f := range p.GoFiles {
 		if strings.HasSuffix(f, "_test.go") {
 			return true
 		}
 	}
 	return false
 }

 // determineRootDirs returns a mapping from absolute directories that could
 // contain code to their corresponding import path prefixes.
 func (state *golistState) determineRootDirs() (map[string]string, error) {
 	env, err := state.getEnv()
 	if err != nil {
 		return nil, err
 	}
 	if env["GOMOD"] != "" {
 		state.rootsOnce.Do(func() {
 			state.rootDirs, state.rootDirsError = state.determineRootDirsModules()
 		})
 	} else {
 		state.rootsOnce.Do(func() {
 			state.rootDirs, state.rootDirsError = state.determineRootDirsGOPATH()
 		})
 	}
 	return state.rootDirs, state.rootDirsError
 }

 func (state *golistState) determineRootDirsModules() (map[string]string, error) {
 	out, err := state.invokeGo("list", "-m", "-json", "all")
 	if err != nil {
 		return nil, err
 	}
 	m := map[string]string{}
 	type jsonMod struct{ Path, Dir string }
 	for dec := json.NewDecoder(out); dec.More(); {
 		mod := new(jsonMod)
 		if err := dec.Decode(mod); err != nil {
 			return nil, err
 		}
 		if mod.Dir != "" && mod.Path != "" {
 			// This is a valid module; add it to the map.
 			absDir, err := filepath.Abs(mod.Dir)
 			if err != nil {
 				return nil, err
 			}
 			m[absDir] = mod.Path
 		}
 	}
 	return m, nil
 }

 func (state *golistState) determineRootDirsGOPATH() (map[string]string, error) {
 	m := map[string]string{}
 	for _, dir := range filepath.SplitList(state.mustGetEnv()["GOPATH"]) {
 		absDir, err := filepath.Abs(dir)
 		if err != nil {
 			return nil, err
 		}
 		m[filepath.Join(absDir, "src")] = ""
 	}
 	return m, nil
 }

 func extractImports(filename string, contents []byte) ([]string, error) {
 	f, err := parser.ParseFile(token.NewFileSet(), filename, contents, parser.ImportsOnly) // TODO(matloob): reuse fileset?
 	if err != nil {
 		return nil, err
 	}
 	var res []string
 	for _, imp := range f.Imports {
 		quotedPath := imp.Path.Value
 		path, err := strconv.Unquote(quotedPath)
 		if err != nil {
 			return nil, err
 		}
 		res = append(res, path)
 	}
 	return res, nil
 }

 // reclaimPackage attempts to reuse a package that failed to load in an overlay.
 //
 // If the package has errors and has no Name, GoFiles, or Imports,
 // then it's possible that it doesn't yet exist on disk.
 func reclaimPackage(pkg *Package, id string, filename string, contents []byte) bool {
 	// TODO(rstambler): Check the message of the actual error?
 	// It differs between $GOPATH and module mode.
 	if pkg.ID != id {
 		return false
 	}
 	if len(pkg.Errors) != 1 {
 		return false
 	}
 	if pkg.Name != "" || pkg.ExportFile != "" {
 		return false
 	}
 	if len(pkg.GoFiles) > 0 || len(pkg.CompiledGoFiles) > 0 || len(pkg.OtherFiles) > 0 {
 		return false
 	}
 	if len(pkg.Imports) > 0 {
 		return false
 	}
 	pkgName, ok := extractPackageName(filename, contents)
 	if !ok {
 		return false
 	}
 	pkg.Name = pkgName
 	pkg.Errors = nil
 	return true
 }

 func extractPackageName(filename string, contents []byte) (string, bool) {
 	// TODO(rstambler): Check the message of the actual error?
 	// It differs between $GOPATH and module mode.
 	f, err := parser.ParseFile(token.NewFileSet(), filename, contents, parser.PackageClauseOnly) // TODO(matloob): reuse fileset?
 	if err != nil {
 		return "", false
 	}
 	return f.Name.Name, true
 }
	package packages

	import (
	"encoding/json"
	"fmt"
	"go/parser"
	"go/token"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	)

	// processGolistOverlay provides rudimentary support for adding
	// files that don't exist on disk to an overlay. The results can be
	// sometimes incorrect.
	// TODO(matloob): Handle unsupported cases, including the following:
	// - determining the correct package to add given a new import path
	func (state golistState) processGolistOverlay(response responseDeduper) (modifiedPkgs, needPkgs []string, err error) {
	havePkgs := make(map[string]string) // importPath -> non-test package ID
	needPkgsSet := make(map[string]bool)
	modifiedPkgsSet := make(map[string]bool)

	for _, pkg := range response.dr.Packages {
	// This is an approximation of import path to id. This can be
	// wrong for tests, vendored packages, and a number of other cases.
	havePkgs[pkg.PkgPath] = pkg.ID
	}

	// If no new imports are added, it is safe to avoid loading any needPkgs.
	// Otherwise, it's hard to tell which package is actually being loaded
	// (due to vendoring) and whether any modified package will show up
	// in the transitive set of dependencies (because new imports are added,
	// potentially modifying the transitive set of dependencies).
	var overlayAddsImports bool

	// If both a package and its test package are created by the overlay, we
	// need the real package first. Process all non-test files before test
	// files, and make the whole process deterministic while we're at it.
	var overlayFiles []string
	for opath := range state.cfg.Overlay {
	overlayFiles = append(overlayFiles, opath)
	}
	sort.Slice(overlayFiles, func(i, j int) bool {
	iTest := strings.HasSuffix(overlayFiles[i], "_test.go")
	jTest := strings.HasSuffix(overlayFiles[j], "_test.go")
	if iTest != jTest {
	return !iTest // non-tests are before tests.
	}
	return overlayFiles[i] < overlayFiles[j]
	})
	for _, opath := range overlayFiles {
	contents := state.cfg.Overlay[opath]
	base := filepath.Base(opath)
	dir := filepath.Dir(opath)
	var pkg *Package // if opath belongs to both a package and its test variant, this will be the test variant
	var testVariantOf *Package // if opath is a test file, this is the package it is testing
	var fileExists bool
	isTestFile := strings.HasSuffix(opath, "_test.go")
	pkgName, ok := extractPackageName(opath, contents)
	if !ok {
	// Don't bother adding a file that doesn't even have a parsable package statement
	// to the overlay.
	continue
	}
	nextPackage:
	for _, p := range response.dr.Packages {
	if pkgName != p.Name && p.ID != "command-line-arguments" {
	continue
	}
	for _, f := range p.GoFiles {
	if !sameFile(filepath.Dir(f), dir) {
	continue
	}
	// Make sure to capture information on the package's test variant, if needed.
	if isTestFile && !hasTestFiles(p) {
	// TODO(matloob): Are there packages other than the 'production' variant
	// of a package that this can match? This shouldn't match the test main package
	// because the file is generated in another directory.
	testVariantOf = p
	continue nextPackage
	}
	// We must have already seen the package of which this is a test variant.
	if pkg != nil && p != pkg && pkg.PkgPath == p.PkgPath {
	if hasTestFiles(p) {
	testVariantOf = pkg
	}
	}
	pkg = p
	if filepath.Base(f) == base {
	fileExists = true
	}
	}
	}
	// The overlay could have included an entirely new package.
	if pkg == nil {
	// Try to find the module or gopath dir the file is contained in.
	// Then for modules, add the module opath to the beginning.
	pkgPath, ok, err := state.getPkgPath(dir)
	if err != nil {
	return nil, nil, err
	}
	if !ok {
	break
	}
	isXTest := strings.HasSuffix(pkgName, "_test")
	if isXTest {
	pkgPath += "_test"
	}
	id := pkgPath
	if isTestFile && !isXTest {
	id = fmt.Sprintf("%s [%s.test]", pkgPath, pkgPath)
	}
	// Try to reclaim a package with the same id if it exists in the response.
	for _, p := range response.dr.Packages {
	if reclaimPackage(p, id, opath, contents) {
	pkg = p
	break
	}
	}
	// Otherwise, create a new package
	if pkg == nil {
	pkg = &Package{PkgPath: pkgPath, ID: id, Name: pkgName, Imports: make(map[string]*Package)}
	response.addPackage(pkg)
	havePkgs[pkg.PkgPath] = id
	// Add the production package's sources for a test variant.
	if isTestFile && !isXTest && testVariantOf != nil {
	pkg.GoFiles = append(pkg.GoFiles, testVariantOf.GoFiles...)
	pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, testVariantOf.CompiledGoFiles...)
	// Add the package under test and its imports to the test variant.
	pkg.forTest = testVariantOf.PkgPath
	for k, v := range testVariantOf.Imports {
	pkg.Imports[k] = &Package{ID: v.ID}
	}
	}
	}
	}
	if !fileExists {
	pkg.GoFiles = append(pkg.GoFiles, opath)
	// TODO(matloob): Adding the file to CompiledGoFiles can exhibit the wrong behavior
	// if the file will be ignored due to its build tags.
	pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, opath)
	modifiedPkgsSet[pkg.ID] = true
	}
	imports, err := extractImports(opath, contents)
	if err != nil {
	// Let the parser or type checker report errors later.
	continue
	}
	for _, imp := range imports {
	if _, found := pkg.Imports[imp]; found {
	continue
	}
	overlayAddsImports = true
	id, ok := havePkgs[imp]
	if !ok {
	var err error
	id, err = state.resolveImport(dir, imp)
	if err != nil {
	return nil, nil, err
	}
	}
	pkg.Imports[imp] = &Package{ID: id}
	// Add dependencies to the non-test variant version of this package as well.
	if testVariantOf != nil {
	testVariantOf.Imports[imp] = &Package{ID: id}
	}
	}
	}

	// toPkgPath guesses the package path given the id.
	toPkgPath := func(sourceDir, id string) (string, error) {
	if i := strings.IndexByte(id, ' '); i >= 0 {
	return state.resolveImport(sourceDir, id[:i])
	}
	return state.resolveImport(sourceDir, id)
	}

	// Now that new packages have been created, do another pass to determine
	// the new set of missing packages.
	for _, pkg := range response.dr.Packages {
	for _, imp := range pkg.Imports {
	if len(pkg.GoFiles) == 0 {
	return nil, nil, fmt.Errorf("cannot resolve imports for package %q with no Go files", pkg.PkgPath)
	}
	pkgPath, err := toPkgPath(filepath.Dir(pkg.GoFiles[0]), imp.ID)
	if err != nil {
	return nil, nil, err
	}
	if _, ok := havePkgs[pkgPath]; !ok {
	needPkgsSet[pkgPath] = true
	}
	}
	}

	if overlayAddsImports {
	needPkgs = make([]string, 0, len(needPkgsSet))
	for pkg := range needPkgsSet {
	needPkgs = append(needPkgs, pkg)
	}
	}
	modifiedPkgs = make([]string, 0, len(modifiedPkgsSet))
	for pkg := range modifiedPkgsSet {
	modifiedPkgs = append(modifiedPkgs, pkg)
	}
	return modifiedPkgs, needPkgs, err
	}

	// resolveImport finds the the ID of a package given its import path.
	// In particular, it will find the right vendored copy when in GOPATH mode.
	func (state *golistState) resolveImport(sourceDir, importPath string) (string, error) {
	env, err := state.getEnv()
	if err != nil {
	return "", err
	}
	if env["GOMOD"] != "" {
	return importPath, nil
	}

	searchDir := sourceDir
	for {
	vendorDir := filepath.Join(searchDir, "vendor")
	exists, ok := state.vendorDirs[vendorDir]
	if !ok {
	info, err := os.Stat(vendorDir)
	exists = err == nil && info.IsDir()
	state.vendorDirs[vendorDir] = exists
	}

	if exists {
	vendoredPath := filepath.Join(vendorDir, importPath)
	if info, err := os.Stat(vendoredPath); err == nil && info.IsDir() {
	// We should probably check for .go files here, but shame on anyone who fools us.
	path, ok, err := state.getPkgPath(vendoredPath)
	if err != nil {
	return "", err
	}
	if ok {
	return path, nil
	}
	}
	}

	// We know we've hit the top of the filesystem when we Dir / and get /,
	// or C:\ and get C:\, etc.
	next := filepath.Dir(searchDir)
	if next == searchDir {
	break
	}
	searchDir = next
	}
	return importPath, nil
	}

	func hasTestFiles(p *Package) bool {
	for _, f := range p.GoFiles {
	if strings.HasSuffix(f, "_test.go") {
	return true
	}
	}
	return false
	}

	// determineRootDirs returns a mapping from absolute directories that could
	// contain code to their corresponding import path prefixes.
	func (state *golistState) determineRootDirs() (map[string]string, error) {
	env, err := state.getEnv()
	if err != nil {
	return nil, err
	}
	if env["GOMOD"] != "" {
	state.rootsOnce.Do(func() {
	state.rootDirs, state.rootDirsError = state.determineRootDirsModules()
	})
	} else {
	state.rootsOnce.Do(func() {
	state.rootDirs, state.rootDirsError = state.determineRootDirsGOPATH()
	})
	}
	return state.rootDirs, state.rootDirsError
	}

	func (state *golistState) determineRootDirsModules() (map[string]string, error) {
	out, err := state.invokeGo("list", "-m", "-json", "all")
	if err != nil {
	return nil, err
	}
	m := map[string]string{}
	type jsonMod struct{ Path, Dir string }
	for dec := json.NewDecoder(out); dec.More(); {
	mod := new(jsonMod)
	if err := dec.Decode(mod); err != nil {
	return nil, err
	}
	if mod.Dir != "" && mod.Path != "" {
	// This is a valid module; add it to the map.
	absDir, err := filepath.Abs(mod.Dir)
	if err != nil {
	return nil, err
	}
	m[absDir] = mod.Path
	}
	}
	return m, nil
	}

	func (state *golistState) determineRootDirsGOPATH() (map[string]string, error) {
	m := map[string]string{}
	for _, dir := range filepath.SplitList(state.mustGetEnv()["GOPATH"]) {
	absDir, err := filepath.Abs(dir)
	if err != nil {
	return nil, err
	}
	m[filepath.Join(absDir, "src")] = ""
	}
	return m, nil
	}

	func extractImports(filename string, contents []byte) ([]string, error) {
	f, err := parser.ParseFile(token.NewFileSet(), filename, contents, parser.ImportsOnly) // TODO(matloob): reuse fileset?
	if err != nil {
	return nil, err
	}
	var res []string
	for _, imp := range f.Imports {
	quotedPath := imp.Path.Value
	path, err := strconv.Unquote(quotedPath)
	if err != nil {
	return nil, err
	}
	res = append(res, path)
	}
	return res, nil
	}

	// reclaimPackage attempts to reuse a package that failed to load in an overlay.
	//
	// If the package has errors and has no Name, GoFiles, or Imports,
	// then it's possible that it doesn't yet exist on disk.
	func reclaimPackage(pkg *Package, id string, filename string, contents []byte) bool {
	// TODO(rstambler): Check the message of the actual error?
	// It differs between $GOPATH and module mode.
	if pkg.ID != id {
	return false
	}
	if len(pkg.Errors) != 1 {
	return false
	}
	if pkg.Name != "" \|\| pkg.ExportFile != "" {
	return false
	}
	if len(pkg.GoFiles) > 0 \|\| len(pkg.CompiledGoFiles) > 0 \|\| len(pkg.OtherFiles) > 0 {
	return false
	}
	if len(pkg.Imports) > 0 {
	return false
	}
	pkgName, ok := extractPackageName(filename, contents)
	if !ok {
	return false
	}
	pkg.Name = pkgName
	pkg.Errors = nil
	return true
	}

	func extractPackageName(filename string, contents []byte) (string, bool) {
	// TODO(rstambler): Check the message of the actual error?
	// It differs between $GOPATH and module mode.
	f, err := parser.ParseFile(token.NewFileSet(), filename, contents, parser.PackageClauseOnly) // TODO(matloob): reuse fileset?
	if err != nil {
	return "", false
	}
	return f.Name.Name, true
	}