vendor/cmd/go/internal/search/search.go - vgo - Git at Google

 // Copyright 2017 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package search

 import (
 	"cmd/go/internal/base"
 	"cmd/go/internal/cfg"
 	"fmt"
 	"go/build"
 	"log"
 	"os"
 	"path"
 	"path/filepath"
 	"regexp"
 	"strings"
 )

 // AllPackages returns all the packages that can be found
 // under the $GOPATH directories and $GOROOT matching pattern.
 // The pattern is either "all" (all packages), "std" (standard packages),
 // "cmd" (standard commands), or a path including "...".
 func AllPackages(pattern string) []string {
 	pkgs := MatchPackages(pattern)
 	if len(pkgs) == 0 {
 		fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
 	}
 	return pkgs
 }

 // AllPackagesInFS is like allPackages but is passed a pattern
 // beginning ./ or ../, meaning it should scan the tree rooted
 // at the given directory. There are ... in the pattern too.
 func AllPackagesInFS(pattern string) []string {
 	pkgs := MatchPackagesInFS(pattern)
 	if len(pkgs) == 0 {
 		fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
 	}
 	return pkgs
 }

 // MatchPackages returns a list of package paths matching pattern
 // (see go help packages for pattern syntax).
 func MatchPackages(pattern string) []string {
 	match := func(string) bool { return true }
 	treeCanMatch := func(string) bool { return true }
 	if !IsMetaPackage(pattern) {
 		match = MatchPattern(pattern)
 		treeCanMatch = TreeCanMatchPattern(pattern)
 	}

 	have := map[string]bool{
 		"builtin": true, // ignore pseudo-package that exists only for documentation
 	}
 	if !cfg.BuildContext.CgoEnabled {
 		have["runtime/cgo"] = true // ignore during walk
 	}
 	var pkgs []string

 	for _, src := range cfg.BuildContext.SrcDirs() {
 		if (pattern == "std" || pattern == "cmd") && src != cfg.GOROOTsrc {
 			continue
 		}
 		src = filepath.Clean(src) + string(filepath.Separator)
 		root := src
 		if pattern == "cmd" {
 			root += "cmd" + string(filepath.Separator)
 		}
 		filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
 			if err != nil || path == src {
 				return nil
 			}

 			want := true
 			// Avoid .foo, _foo, and testdata directory trees.
 			_, elem := filepath.Split(path)
 			if strings.HasPrefix(elem, ".") || strings.HasPrefix(elem, "_") || elem == "testdata" {
 				want = false
 			}

 			name := filepath.ToSlash(path[len(src):])
 			if pattern == "std" && (!IsStandardImportPath(name) || name == "cmd") {
 				// The name "std" is only the standard library.
 				// If the name is cmd, it's the root of the command tree.
 				want = false
 			}
 			if !treeCanMatch(name) {
 				want = false
 			}

 			if !fi.IsDir() {
 				if fi.Mode()&os.ModeSymlink != 0 && want {
 					if target, err := os.Stat(path); err == nil && target.IsDir() {
 						fmt.Fprintf(os.Stderr, "warning: ignoring symlink %s\n", path)
 					}
 				}
 				return nil
 			}
 			if !want {
 				return filepath.SkipDir
 			}

 			if have[name] {
 				return nil
 			}
 			have[name] = true
 			if !match(name) {
 				return nil
 			}
 			pkg, err := cfg.BuildContext.ImportDir(path, 0)
 			if err != nil {
 				if _, noGo := err.(*build.NoGoError); noGo {
 					return nil
 				}
 			}

 			// If we are expanding "cmd", skip main
 			// packages under cmd/vendor. At least as of
 			// March, 2017, there is one there for the
 			// vendored pprof tool.
 			if pattern == "cmd" && strings.HasPrefix(pkg.ImportPath, "cmd/vendor") && pkg.Name == "main" {
 				return nil
 			}

 			pkgs = append(pkgs, name)
 			return nil
 		})
 	}
 	return pkgs
 }

 var modRoot string

 func SetModRoot(dir string) {
 	modRoot = dir
 }

 // MatchPackagesInFS returns a list of package paths matching pattern,
 // which must begin with ./ or ../
 // (see go help packages for pattern syntax).
 func MatchPackagesInFS(pattern string) []string {
 	// Find directory to begin the scan.
 	// Could be smarter but this one optimization
 	// is enough for now, since ... is usually at the
 	// end of a path.
 	i := strings.Index(pattern, "...")
 	dir, _ := path.Split(pattern[:i])

 	// pattern begins with ./ or ../.
 	// path.Clean will discard the ./ but not the ../.
 	// We need to preserve the ./ for pattern matching
 	// and in the returned import paths.
 	prefix := ""
 	if strings.HasPrefix(pattern, "./") {
 		prefix = "./"
 	}
 	match := MatchPattern(pattern)

 	if modRoot != "" {
 		abs, err := filepath.Abs(dir)
 		if err != nil {
 			base.Fatalf("go: %v", err)
 		}
 		if !hasFilepathPrefix(abs, modRoot) {
 			base.Fatalf("go: pattern %s refers to dir %s, outside module root %s", pattern, abs, modRoot)
 			return nil
 		}
 	}

 	var pkgs []string
 	filepath.Walk(dir, func(path string, fi os.FileInfo, err error) error {
 		if err != nil || !fi.IsDir() {
 			return nil
 		}
 		top := false
 		if path == dir {
 			// filepath.Walk starts at dir and recurses. For the recursive case,
 			// the path is the result of filepath.Join, which calls filepath.Clean.
 			// The initial case is not Cleaned, though, so we do this explicitly.
 			//
 			// This converts a path like "./io/" to "io". Without this step, running
 			// "cd $GOROOT/src; go list ./io/..." would incorrectly skip the io
 			// package, because prepending the prefix "./" to the unclean path would
 			// result in "././io", and match("././io") returns false.
 			top = true
 			path = filepath.Clean(path)
 		}

 		// Avoid .foo, _foo, and testdata directory trees, but do not avoid "." or "..".
 		_, elem := filepath.Split(path)
 		dot := strings.HasPrefix(elem, ".") && elem != "." && elem != ".."
 		if dot || strings.HasPrefix(elem, "_") || elem == "testdata" {
 			return filepath.SkipDir
 		}

 		if !top && cfg.ModulesEnabled {
 			// Ignore other modules found in subdirectories.
 			if _, err := os.Stat(filepath.Join(path, "go.mod")); err == nil {
 				return filepath.SkipDir
 			}
 		}

 		name := prefix + filepath.ToSlash(path)
 		if !match(name) {
 			return nil
 		}

 		// We keep the directory if we can import it, or if we can't import it
 		// due to invalid Go source files. This means that directories containing
 		// parse errors will be built (and fail) instead of being silently skipped
 		// as not matching the pattern. Go 1.5 and earlier skipped, but that
 		// behavior means people miss serious mistakes.
 		// See golang.org/issue/11407.
 		if p, err := cfg.BuildContext.ImportDir(path, 0); err != nil && (p == nil || len(p.InvalidGoFiles) == 0) {
 			if _, noGo := err.(*build.NoGoError); !noGo {
 				log.Print(err)
 			}
 			return nil
 		}
 		pkgs = append(pkgs, name)
 		return nil
 	})
 	return pkgs
 }

 // TreeCanMatchPattern(pattern)(name) reports whether
 // name or children of name can possibly match pattern.
 // Pattern is the same limited glob accepted by matchPattern.
 func TreeCanMatchPattern(pattern string) func(name string) bool {
 	wildCard := false
 	if i := strings.Index(pattern, "..."); i >= 0 {
 		wildCard = true
 		pattern = pattern[:i]
 	}
 	return func(name string) bool {
 		return len(name) <= len(pattern) && hasPathPrefix(pattern, name) ||
 			wildCard && strings.HasPrefix(name, pattern)
 	}
 }

 // MatchPattern(pattern)(name) reports whether
 // name matches pattern. Pattern is a limited glob
 // pattern in which '...' means 'any string' and there
 // is no other special syntax.
 // Unfortunately, there are two special cases. Quoting "go help packages":
 //
 // First, /... at the end of the pattern can match an empty string,
 // so that net/... matches both net and packages in its subdirectories, like net/http.
 // Second, any slash-separted pattern element containing a wildcard never
 // participates in a match of the "vendor" element in the path of a vendored
 // package, so that ./... does not match packages in subdirectories of
 // ./vendor or ./mycode/vendor, but ./vendor/... and ./mycode/vendor/... do.
 // Note, however, that a directory named vendor that itself contains code
 // is not a vendored package: cmd/vendor would be a command named vendor,
 // and the pattern cmd/... matches it.
 func MatchPattern(pattern string) func(name string) bool {
 	// Convert pattern to regular expression.
 	// The strategy for the trailing /... is to nest it in an explicit ? expression.
 	// The strategy for the vendor exclusion is to change the unmatchable
 	// vendor strings to a disallowed code point (vendorChar) and to use
 	// "(anything but that codepoint)*" as the implementation of the ... wildcard.
 	// This is a bit complicated but the obvious alternative,
 	// namely a hand-written search like in most shell glob matchers,
 	// is too easy to make accidentally exponential.
 	// Using package regexp guarantees linear-time matching.

 	const vendorChar = "\x00"

 	if strings.Contains(pattern, vendorChar) {
 		return func(name string) bool { return false }
 	}

 	re := regexp.QuoteMeta(pattern)
 	re = replaceVendor(re, vendorChar)
 	switch {
 	case strings.HasSuffix(re, `/`+vendorChar+`/\.\.\.`):
 		re = strings.TrimSuffix(re, `/`+vendorChar+`/\.\.\.`) + `(/vendor|/` + vendorChar + `/\.\.\.)`
 	case re == vendorChar+`/\.\.\.`:
 		re = `(/vendor|/` + vendorChar + `/\.\.\.)`
 	case strings.HasSuffix(re, `/\.\.\.`):
 		re = strings.TrimSuffix(re, `/\.\.\.`) + `(/\.\.\.)?`
 	}
 	re = strings.Replace(re, `\.\.\.`, `[^`+vendorChar+`]*`, -1)

 	reg := regexp.MustCompile(`^` + re + `$`)

 	return func(name string) bool {
 		if strings.Contains(name, vendorChar) {
 			return false
 		}
 		return reg.MatchString(replaceVendor(name, vendorChar))
 	}
 }

 // replaceVendor returns the result of replacing
 // non-trailing vendor path elements in x with repl.
 func replaceVendor(x, repl string) string {
 	if !strings.Contains(x, "vendor") {
 		return x
 	}
 	elem := strings.Split(x, "/")
 	for i := 0; i < len(elem)-1; i++ {
 		if elem[i] == "vendor" {
 			elem[i] = repl
 		}
 	}
 	return strings.Join(elem, "/")
 }

 // ImportPaths returns the import paths to use for the given command line.
 func ImportPaths(args []string) []string {
 	args = CleanImportPaths(args)
 	var out []string
 	for _, a := range args {
 		if IsMetaPackage(a) {
 			out = append(out, AllPackages(a)...)
 			continue
 		}
 		if strings.Contains(a, "...") {
 			if build.IsLocalImport(a) {
 				out = append(out, AllPackagesInFS(a)...)
 			} else {
 				out = append(out, AllPackages(a)...)
 			}
 			continue
 		}
 		out = append(out, a)
 	}
 	return out
 }

 // CleanImportPaths returns the import paths to use for the given
 // command line, but it does no wildcard expansion.
 func CleanImportPaths(args []string) []string {
 	if len(args) == 0 {
 		return []string{"."}
 	}
 	var out []string
 	for _, a := range args {
 		// Arguments are supposed to be import paths, but
 		// as a courtesy to Windows developers, rewrite \ to /
 		// in command-line arguments. Handles .\... and so on.
 		if filepath.Separator == '\\' {
 			a = strings.Replace(a, `\`, `/`, -1)
 		}

 		// Put argument in canonical form, but preserve leading ./.
 		if strings.HasPrefix(a, "./") {
 			a = "./" + path.Clean(a)
 			if a == "./." {
 				a = "."
 			}
 		} else {
 			a = path.Clean(a)
 		}
 		out = append(out, a)
 	}
 	return out
 }

 // ImportPathsNoDotExpansion returns the import paths to use for the given
 // command line, but it does no ... expansion.
 // TODO(rsc): Delete once old go get is gone.
 func ImportPathsNoDotExpansion(args []string) []string {
 	args = CleanImportPaths(args)
 	var out []string
 	for _, a := range args {
 		if IsMetaPackage(a) {
 			out = append(out, AllPackages(a)...)
 			continue
 		}
 		out = append(out, a)
 	}
 	return out
 }

 // IsMetaPackage checks if name is a reserved package name that expands to multiple packages.
 func IsMetaPackage(name string) bool {
 	return name == "std" || name == "cmd" || name == "all"
 }

 // hasPathPrefix reports whether the path s begins with the
 // elements in prefix.
 func hasPathPrefix(s, prefix string) bool {
 	switch {
 	default:
 		return false
 	case len(s) == len(prefix):
 		return s == prefix
 	case len(s) > len(prefix):
 		if prefix != "" && prefix[len(prefix)-1] == '/' {
 			return strings.HasPrefix(s, prefix)
 		}
 		return s[len(prefix)] == '/' && s[:len(prefix)] == prefix
 	}
 }

 // hasFilepathPrefix reports whether the path s begins with the
 // elements in prefix.
 func hasFilepathPrefix(s, prefix string) bool {
 	switch {
 	default:
 		return false
 	case len(s) == len(prefix):
 		return s == prefix
 	case len(s) > len(prefix):
 		if prefix != "" && prefix[len(prefix)-1] == filepath.Separator {
 			return strings.HasPrefix(s, prefix)
 		}
 		return s[len(prefix)] == filepath.Separator && s[:len(prefix)] == prefix
 	}
 }

 // IsStandardImportPath reports whether $GOROOT/src/path should be considered
 // part of the standard distribution. For historical reasons we allow people to add
 // their own code to $GOROOT instead of using $GOPATH, but we assume that
 // code will start with a domain name (dot in the first element).
 //
 // Note that this function is meant to evaluate whether a directory found in GOROOT
 // should be treated as part of the standard library. It should not be used to decide
 // that a directory found in GOPATH should be rejected: directories in GOPATH
 // need not have dots in the first element, and they just take their chances
 // with future collisions in the standard library.
 func IsStandardImportPath(path string) bool {
 	i := strings.Index(path, "/")
 	if i < 0 {
 		i = len(path)
 	}
 	elem := path[:i]
 	return !strings.Contains(elem, ".")
 }

 // IsRelativePath reports whether pattern should be interpreted as a directory
 // path relative to the current directory, as opposed to a pattern matching
 // import paths.
 func IsRelativePath(pattern string) bool {
 	return strings.HasPrefix(pattern, "./") || strings.HasPrefix(pattern, "../") || pattern == "." || pattern == ".."
 }
	// Copyright 2017 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package search

	import (
	"cmd/go/internal/base"
	"cmd/go/internal/cfg"
	"fmt"
	"go/build"
	"log"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"strings"
	)

	// AllPackages returns all the packages that can be found
	// under the $GOPATH directories and $GOROOT matching pattern.
	// The pattern is either "all" (all packages), "std" (standard packages),
	// "cmd" (standard commands), or a path including "...".
	func AllPackages(pattern string) []string {
	pkgs := MatchPackages(pattern)
	if len(pkgs) == 0 {
	fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
	}
	return pkgs
	}

	// AllPackagesInFS is like allPackages but is passed a pattern
	// beginning ./ or ../, meaning it should scan the tree rooted
	// at the given directory. There are ... in the pattern too.
	func AllPackagesInFS(pattern string) []string {
	pkgs := MatchPackagesInFS(pattern)
	if len(pkgs) == 0 {
	fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
	}
	return pkgs
	}

	// MatchPackages returns a list of package paths matching pattern
	// (see go help packages for pattern syntax).
	func MatchPackages(pattern string) []string {
	match := func(string) bool { return true }
	treeCanMatch := func(string) bool { return true }
	if !IsMetaPackage(pattern) {
	match = MatchPattern(pattern)
	treeCanMatch = TreeCanMatchPattern(pattern)
	}

	have := map[string]bool{
	"builtin": true, // ignore pseudo-package that exists only for documentation
	}
	if !cfg.BuildContext.CgoEnabled {
	have["runtime/cgo"] = true // ignore during walk
	}
	var pkgs []string

	for _, src := range cfg.BuildContext.SrcDirs() {
	if (pattern == "std" \|\| pattern == "cmd") && src != cfg.GOROOTsrc {
	continue
	}
	src = filepath.Clean(src) + string(filepath.Separator)
	root := src
	if pattern == "cmd" {
	root += "cmd" + string(filepath.Separator)
	}
	filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
	if err != nil \|\| path == src {
	return nil
	}

	want := true
	// Avoid .foo, _foo, and testdata directory trees.
	_, elem := filepath.Split(path)
	if strings.HasPrefix(elem, ".") \|\| strings.HasPrefix(elem, "_") \|\| elem == "testdata" {
	want = false
	}

	name := filepath.ToSlash(path[len(src):])
	if pattern == "std" && (!IsStandardImportPath(name) \|\| name == "cmd") {
	// The name "std" is only the standard library.
	// If the name is cmd, it's the root of the command tree.
	want = false
	}
	if !treeCanMatch(name) {
	want = false
	}

	if !fi.IsDir() {
	if fi.Mode()&os.ModeSymlink != 0 && want {
	if target, err := os.Stat(path); err == nil && target.IsDir() {
	fmt.Fprintf(os.Stderr, "warning: ignoring symlink %s\n", path)
	}
	}
	return nil
	}
	if !want {
	return filepath.SkipDir
	}

	if have[name] {
	return nil
	}
	have[name] = true
	if !match(name) {
	return nil
	}
	pkg, err := cfg.BuildContext.ImportDir(path, 0)
	if err != nil {
	if _, noGo := err.(*build.NoGoError); noGo {
	return nil
	}
	}

	// If we are expanding "cmd", skip main
	// packages under cmd/vendor. At least as of
	// March, 2017, there is one there for the
	// vendored pprof tool.
	if pattern == "cmd" && strings.HasPrefix(pkg.ImportPath, "cmd/vendor") && pkg.Name == "main" {
	return nil
	}

	pkgs = append(pkgs, name)
	return nil
	})
	}
	return pkgs
	}

	var modRoot string

	func SetModRoot(dir string) {
	modRoot = dir
	}

	// MatchPackagesInFS returns a list of package paths matching pattern,
	// which must begin with ./ or ../
	// (see go help packages for pattern syntax).
	func MatchPackagesInFS(pattern string) []string {
	// Find directory to begin the scan.
	// Could be smarter but this one optimization
	// is enough for now, since ... is usually at the
	// end of a path.
	i := strings.Index(pattern, "...")
	dir, _ := path.Split(pattern[:i])

	// pattern begins with ./ or ../.
	// path.Clean will discard the ./ but not the ../.
	// We need to preserve the ./ for pattern matching
	// and in the returned import paths.
	prefix := ""
	if strings.HasPrefix(pattern, "./") {
	prefix = "./"
	}
	match := MatchPattern(pattern)

	if modRoot != "" {
	abs, err := filepath.Abs(dir)
	if err != nil {
	base.Fatalf("go: %v", err)
	}
	if !hasFilepathPrefix(abs, modRoot) {
	base.Fatalf("go: pattern %s refers to dir %s, outside module root %s", pattern, abs, modRoot)
	return nil
	}
	}

	var pkgs []string
	filepath.Walk(dir, func(path string, fi os.FileInfo, err error) error {
	if err != nil \|\| !fi.IsDir() {
	return nil
	}
	top := false
	if path == dir {
	// filepath.Walk starts at dir and recurses. For the recursive case,
	// the path is the result of filepath.Join, which calls filepath.Clean.
	// The initial case is not Cleaned, though, so we do this explicitly.
	//
	// This converts a path like "./io/" to "io". Without this step, running
	// "cd $GOROOT/src; go list ./io/..." would incorrectly skip the io
	// package, because prepending the prefix "./" to the unclean path would
	// result in "././io", and match("././io") returns false.
	top = true
	path = filepath.Clean(path)
	}

	// Avoid .foo, _foo, and testdata directory trees, but do not avoid "." or "..".
	_, elem := filepath.Split(path)
	dot := strings.HasPrefix(elem, ".") && elem != "." && elem != ".."
	if dot \|\| strings.HasPrefix(elem, "_") \|\| elem == "testdata" {
	return filepath.SkipDir
	}

	if !top && cfg.ModulesEnabled {
	// Ignore other modules found in subdirectories.
	if _, err := os.Stat(filepath.Join(path, "go.mod")); err == nil {
	return filepath.SkipDir
	}
	}

	name := prefix + filepath.ToSlash(path)
	if !match(name) {
	return nil
	}

	// We keep the directory if we can import it, or if we can't import it
	// due to invalid Go source files. This means that directories containing
	// parse errors will be built (and fail) instead of being silently skipped
	// as not matching the pattern. Go 1.5 and earlier skipped, but that
	// behavior means people miss serious mistakes.
	// See golang.org/issue/11407.
	if p, err := cfg.BuildContext.ImportDir(path, 0); err != nil && (p == nil \|\| len(p.InvalidGoFiles) == 0) {
	if _, noGo := err.(*build.NoGoError); !noGo {
	log.Print(err)
	}
	return nil
	}
	pkgs = append(pkgs, name)
	return nil
	})
	return pkgs
	}

	// TreeCanMatchPattern(pattern)(name) reports whether
	// name or children of name can possibly match pattern.
	// Pattern is the same limited glob accepted by matchPattern.
	func TreeCanMatchPattern(pattern string) func(name string) bool {
	wildCard := false
	if i := strings.Index(pattern, "..."); i >= 0 {
	wildCard = true
	pattern = pattern[:i]
	}
	return func(name string) bool {
	return len(name) <= len(pattern) && hasPathPrefix(pattern, name) \|\|
	wildCard && strings.HasPrefix(name, pattern)
	}
	}

	// MatchPattern(pattern)(name) reports whether
	// name matches pattern. Pattern is a limited glob
	// pattern in which '...' means 'any string' and there
	// is no other special syntax.
	// Unfortunately, there are two special cases. Quoting "go help packages":
	//
	// First, /... at the end of the pattern can match an empty string,
	// so that net/... matches both net and packages in its subdirectories, like net/http.
	// Second, any slash-separted pattern element containing a wildcard never
	// participates in a match of the "vendor" element in the path of a vendored
	// package, so that ./... does not match packages in subdirectories of
	// ./vendor or ./mycode/vendor, but ./vendor/... and ./mycode/vendor/... do.
	// Note, however, that a directory named vendor that itself contains code
	// is not a vendored package: cmd/vendor would be a command named vendor,
	// and the pattern cmd/... matches it.
	func MatchPattern(pattern string) func(name string) bool {
	// Convert pattern to regular expression.
	// The strategy for the trailing /... is to nest it in an explicit ? expression.
	// The strategy for the vendor exclusion is to change the unmatchable
	// vendor strings to a disallowed code point (vendorChar) and to use
	// "(anything but that codepoint)*" as the implementation of the ... wildcard.
	// This is a bit complicated but the obvious alternative,
	// namely a hand-written search like in most shell glob matchers,
	// is too easy to make accidentally exponential.
	// Using package regexp guarantees linear-time matching.

	const vendorChar = "\x00"

	if strings.Contains(pattern, vendorChar) {
	return func(name string) bool { return false }
	}

	re := regexp.QuoteMeta(pattern)
	re = replaceVendor(re, vendorChar)
	switch {
	case strings.HasSuffix(re, `/`+vendorChar+`/\.\.\.`):
	re = strings.TrimSuffix(re, `/`+vendorChar+`/\.\.\.`) + `(/vendor\|/` + vendorChar + `/\.\.\.)`
	case re == vendorChar+`/\.\.\.`:
	re = `(/vendor\|/` + vendorChar + `/\.\.\.)`
	case strings.HasSuffix(re, `/\.\.\.`):
	re = strings.TrimSuffix(re, `/\.\.\.`) + `(/\.\.\.)?`
	}
	re = strings.Replace(re, `\.\.\.`, `[^`+vendorChar+`]*`, -1)

	reg := regexp.MustCompile(`^` + re + `$`)

	return func(name string) bool {
	if strings.Contains(name, vendorChar) {
	return false
	}
	return reg.MatchString(replaceVendor(name, vendorChar))
	}
	}

	// replaceVendor returns the result of replacing
	// non-trailing vendor path elements in x with repl.
	func replaceVendor(x, repl string) string {
	if !strings.Contains(x, "vendor") {
	return x
	}
	elem := strings.Split(x, "/")
	for i := 0; i < len(elem)-1; i++ {
	if elem[i] == "vendor" {
	elem[i] = repl
	}
	}
	return strings.Join(elem, "/")
	}

	// ImportPaths returns the import paths to use for the given command line.
	func ImportPaths(args []string) []string {
	args = CleanImportPaths(args)
	var out []string
	for _, a := range args {
	if IsMetaPackage(a) {
	out = append(out, AllPackages(a)...)
	continue
	}
	if strings.Contains(a, "...") {
	if build.IsLocalImport(a) {
	out = append(out, AllPackagesInFS(a)...)
	} else {
	out = append(out, AllPackages(a)...)
	}
	continue
	}
	out = append(out, a)
	}
	return out
	}

	// CleanImportPaths returns the import paths to use for the given
	// command line, but it does no wildcard expansion.
	func CleanImportPaths(args []string) []string {
	if len(args) == 0 {
	return []string{"."}
	}
	var out []string
	for _, a := range args {
	// Arguments are supposed to be import paths, but
	// as a courtesy to Windows developers, rewrite \ to /
	// in command-line arguments. Handles .\... and so on.
	if filepath.Separator == '\\' {
	a = strings.Replace(a, `\`, `/`, -1)
	}

	// Put argument in canonical form, but preserve leading ./.
	if strings.HasPrefix(a, "./") {
	a = "./" + path.Clean(a)
	if a == "./." {
	a = "."
	}
	} else {
	a = path.Clean(a)
	}
	out = append(out, a)
	}
	return out
	}

	// ImportPathsNoDotExpansion returns the import paths to use for the given
	// command line, but it does no ... expansion.
	// TODO(rsc): Delete once old go get is gone.
	func ImportPathsNoDotExpansion(args []string) []string {
	args = CleanImportPaths(args)
	var out []string
	for _, a := range args {
	if IsMetaPackage(a) {
	out = append(out, AllPackages(a)...)
	continue
	}
	out = append(out, a)
	}
	return out
	}

	// IsMetaPackage checks if name is a reserved package name that expands to multiple packages.
	func IsMetaPackage(name string) bool {
	return name == "std" \|\| name == "cmd" \|\| name == "all"
	}

	// hasPathPrefix reports whether the path s begins with the
	// elements in prefix.
	func hasPathPrefix(s, prefix string) bool {
	switch {
	default:
	return false
	case len(s) == len(prefix):
	return s == prefix
	case len(s) > len(prefix):
	if prefix != "" && prefix[len(prefix)-1] == '/' {
	return strings.HasPrefix(s, prefix)
	}
	return s[len(prefix)] == '/' && s[:len(prefix)] == prefix
	}
	}

	// hasFilepathPrefix reports whether the path s begins with the
	// elements in prefix.
	func hasFilepathPrefix(s, prefix string) bool {
	switch {
	default:
	return false
	case len(s) == len(prefix):
	return s == prefix
	case len(s) > len(prefix):
	if prefix != "" && prefix[len(prefix)-1] == filepath.Separator {
	return strings.HasPrefix(s, prefix)
	}
	return s[len(prefix)] == filepath.Separator && s[:len(prefix)] == prefix
	}
	}

	// IsStandardImportPath reports whether $GOROOT/src/path should be considered
	// part of the standard distribution. For historical reasons we allow people to add
	// their own code to $GOROOT instead of using $GOPATH, but we assume that
	// code will start with a domain name (dot in the first element).
	//
	// Note that this function is meant to evaluate whether a directory found in GOROOT
	// should be treated as part of the standard library. It should not be used to decide
	// that a directory found in GOPATH should be rejected: directories in GOPATH
	// need not have dots in the first element, and they just take their chances
	// with future collisions in the standard library.
	func IsStandardImportPath(path string) bool {
	i := strings.Index(path, "/")
	if i < 0 {
	i = len(path)
	}
	elem := path[:i]
	return !strings.Contains(elem, ".")
	}

	// IsRelativePath reports whether pattern should be interpreted as a directory
	// path relative to the current directory, as opposed to a pattern matching
	// import paths.
	func IsRelativePath(pattern string) bool {
	return strings.HasPrefix(pattern, "./") \|\| strings.HasPrefix(pattern, "../") \|\| pattern == "." \|\| pattern == ".."
	}