added vendor

vendor/golang.org/x/tools/imports/fix.go

@@ -0,0 +1,934 @@
+// Copyright 2013 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 imports
+
+import (
+	"context"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+
+	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/internal/gopathwalk"
+)
+
+// Debug controls verbose logging.
+var Debug = false
+
+// LocalPrefix is a comma-separated string of import path prefixes, which, if
+// set, instructs Process to sort the import paths with the given prefixes
+// into another group after 3rd-party packages.
+var LocalPrefix string
+
+func localPrefixes() []string {
+	if LocalPrefix != "" {
+		return strings.Split(LocalPrefix, ",")
+	}
+	return nil
+}
+
+// importToGroup is a list of functions which map from an import path to
+// a group number.
+var importToGroup = []func(importPath string) (num int, ok bool){
+	func(importPath string) (num int, ok bool) {
+		for _, p := range localPrefixes() {
+			if strings.HasPrefix(importPath, p) || strings.TrimSuffix(p, "/") == importPath {
+				return 3, true
+			}
+		}
+		return
+	},
+	func(importPath string) (num int, ok bool) {
+		if strings.HasPrefix(importPath, "appengine") {
+			return 2, true
+		}
+		return
+	},
+	func(importPath string) (num int, ok bool) {
+		if strings.Contains(importPath, ".") {
+			return 1, true
+		}
+		return
+	},
+}
+
+func importGroup(importPath string) int {
+	for _, fn := range importToGroup {
+		if n, ok := fn(importPath); ok {
+			return n
+		}
+	}
+	return 0
+}
+
+// importInfo is a summary of information about one import.
+type importInfo struct {
+	Path  string // full import path (e.g. "crypto/rand")
+	Alias string // import alias, if present (e.g. "crand")
+}
+
+// packageInfo is a summary of features found in a package.
+type packageInfo struct {
+	Globals map[string]bool       // symbol => true
+	Imports map[string]importInfo // pkg base name or alias => info
+	// refs are a set of package references currently satisfied by imports.
+	// first key: either base package (e.g. "fmt") or renamed package
+	// second key: referenced package symbol (e.g. "Println")
+	Refs map[string]map[string]bool
+}
+
+// dirPackageInfo exposes the dirPackageInfoFile function so that it can be overridden.
+var dirPackageInfo = dirPackageInfoFile
+
+// dirPackageInfoFile gets information from other files in the package.
+func dirPackageInfoFile(pkgName, srcDir, filename string) (*packageInfo, error) {
+	considerTests := strings.HasSuffix(filename, "_test.go")
+
+	fileBase := filepath.Base(filename)
+	packageFileInfos, err := ioutil.ReadDir(srcDir)
+	if err != nil {
+		return nil, err
+	}
+
+	info := &packageInfo{
+		Globals: make(map[string]bool),
+		Imports: make(map[string]importInfo),
+		Refs:    make(map[string]map[string]bool),
+	}
+
+	visitor := collectReferences(info.Refs)
+	for _, fi := range packageFileInfos {
+		if fi.Name() == fileBase || !strings.HasSuffix(fi.Name(), ".go") {
+			continue
+		}
+		if !considerTests && strings.HasSuffix(fi.Name(), "_test.go") {
+			continue
+		}
+
+		fileSet := token.NewFileSet()
+		root, err := parser.ParseFile(fileSet, filepath.Join(srcDir, fi.Name()), nil, 0)
+		if err != nil {
+			continue
+		}
+
+		for _, decl := range root.Decls {
+			genDecl, ok := decl.(*ast.GenDecl)
+			if !ok {
+				continue
+			}
+
+			for _, spec := range genDecl.Specs {
+				valueSpec, ok := spec.(*ast.ValueSpec)
+				if !ok {
+					continue
+				}
+				info.Globals[valueSpec.Names[0].Name] = true
+			}
+		}
+
+		for _, imp := range root.Imports {
+			impInfo := importInfo{Path: strings.Trim(imp.Path.Value, `"`)}
+			name := path.Base(impInfo.Path)
+			if imp.Name != nil {
+				name = strings.Trim(imp.Name.Name, `"`)
+				impInfo.Alias = name
+			}
+			info.Imports[name] = impInfo
+		}
+
+		ast.Walk(visitor, root)
+	}
+	return info, nil
+}
+
+// collectReferences returns a visitor that collects all exported package
+// references
+func collectReferences(refs map[string]map[string]bool) visitFn {
+	var visitor visitFn
+	visitor = func(node ast.Node) ast.Visitor {
+		if node == nil {
+			return visitor
+		}
+		switch v := node.(type) {
+		case *ast.SelectorExpr:
+			xident, ok := v.X.(*ast.Ident)
+			if !ok {
+				break
+			}
+			if xident.Obj != nil {
+				// if the parser can resolve it, it's not a package ref
+				break
+			}
+			pkgName := xident.Name
+			r := refs[pkgName]
+			if r == nil {
+				r = make(map[string]bool)
+				refs[pkgName] = r
+			}
+			if ast.IsExported(v.Sel.Name) {
+				r[v.Sel.Name] = true
+			}
+		}
+		return visitor
+	}
+	return visitor
+}
+
+func fixImports(fset *token.FileSet, f *ast.File, filename string) (added []string, err error) {
+	// refs are a set of possible package references currently unsatisfied by imports.
+	// first key: either base package (e.g. "fmt") or renamed package
+	// second key: referenced package symbol (e.g. "Println")
+	refs := make(map[string]map[string]bool)
+
+	// decls are the current package imports. key is base package or renamed package.
+	decls := make(map[string]*ast.ImportSpec)
+
+	abs, err := filepath.Abs(filename)
+	if err != nil {
+		return nil, err
+	}
+	srcDir := filepath.Dir(abs)
+	if Debug {
+		log.Printf("fixImports(filename=%q), abs=%q, srcDir=%q ...", filename, abs, srcDir)
+	}
+
+	var packageInfo *packageInfo
+	var loadedPackageInfo bool
+
+	// collect potential uses of packages.
+	var visitor visitFn
+	visitor = visitFn(func(node ast.Node) ast.Visitor {
+		if node == nil {
+			return visitor
+		}
+		switch v := node.(type) {
+		case *ast.ImportSpec:
+			if v.Name != nil {
+				decls[v.Name.Name] = v
+				break
+			}
+			ipath := strings.Trim(v.Path.Value, `"`)
+			if ipath == "C" {
+				break
+			}
+			local := importPathToName(ipath, srcDir)
+			decls[local] = v
+		case *ast.SelectorExpr:
+			xident, ok := v.X.(*ast.Ident)
+			if !ok {
+				break
+			}
+			if xident.Obj != nil {
+				// if the parser can resolve it, it's not a package ref
+				break
+			}
+			pkgName := xident.Name
+			if refs[pkgName] == nil {
+				refs[pkgName] = make(map[string]bool)
+			}
+			if !loadedPackageInfo {
+				loadedPackageInfo = true
+				packageInfo, _ = dirPackageInfo(f.Name.Name, srcDir, filename)
+			}
+			if decls[pkgName] == nil && (packageInfo == nil || !packageInfo.Globals[pkgName]) {
+				refs[pkgName][v.Sel.Name] = true
+			}
+		}
+		return visitor
+	})
+	ast.Walk(visitor, f)
+
+	// Nil out any unused ImportSpecs, to be removed in following passes
+	unusedImport := map[string]string{}
+	for pkg, is := range decls {
+		if refs[pkg] == nil && pkg != "_" && pkg != "." {
+			name := ""
+			if is.Name != nil {
+				name = is.Name.Name
+			}
+			unusedImport[strings.Trim(is.Path.Value, `"`)] = name
+		}
+	}
+	for ipath, name := range unusedImport {
+		if ipath == "C" {
+			// Don't remove cgo stuff.
+			continue
+		}
+		astutil.DeleteNamedImport(fset, f, name, ipath)
+	}
+
+	for pkgName, symbols := range refs {
+		if len(symbols) == 0 {
+			// skip over packages already imported
+			delete(refs, pkgName)
+		}
+	}
+
+	// Fast path, all references already imported.
+	if len(refs) == 0 {
+		return nil, nil
+	}
+
+	// Can assume this will be necessary in all cases now.
+	if !loadedPackageInfo {
+		packageInfo, _ = dirPackageInfo(f.Name.Name, srcDir, filename)
+	}
+
+	// Search for imports matching potential package references.
+	type result struct {
+		ipath string // import path
+		name  string // optional name to rename import as
+	}
+	results := make(chan result, len(refs))
+
+	ctx, cancel := context.WithCancel(context.TODO())
+	var wg sync.WaitGroup
+	defer func() {
+		cancel()
+		wg.Wait()
+	}()
+	var (
+		firstErr     error
+		firstErrOnce sync.Once
+	)
+	for pkgName, symbols := range refs {
+		wg.Add(1)
+		go func(pkgName string, symbols map[string]bool) {
+			defer wg.Done()
+
+			if packageInfo != nil {
+				sibling := packageInfo.Imports[pkgName]
+				if sibling.Path != "" {
+					refs := packageInfo.Refs[pkgName]
+					for symbol := range symbols {
+						if refs[symbol] {
+							results <- result{ipath: sibling.Path, name: sibling.Alias}
+							return
+						}
+					}
+				}
+			}
+
+			ipath, rename, err := findImport(ctx, pkgName, symbols, filename)
+			if err != nil {
+				firstErrOnce.Do(func() {
+					firstErr = err
+					cancel()
+				})
+				return
+			}
+
+			if ipath == "" {
+				return // No matching package.
+			}
+
+			r := result{ipath: ipath}
+			if rename {
+				r.name = pkgName
+			}
+			results <- r
+			return
+		}(pkgName, symbols)
+	}
+	go func() {
+		wg.Wait()
+		close(results)
+	}()
+
+	for result := range results {
+		if result.name != "" {
+			astutil.AddNamedImport(fset, f, result.name, result.ipath)
+		} else {
+			astutil.AddImport(fset, f, result.ipath)
+		}
+		added = append(added, result.ipath)
+	}
+
+	if firstErr != nil {
+		return nil, firstErr
+	}
+	return added, nil
+}
+
+// importPathToName returns the package name for the given import path.
+var importPathToName func(importPath, srcDir string) (packageName string) = importPathToNameGoPath
+
+// importPathToNameBasic assumes the package name is the base of import path,
+// except that if the path ends in foo/vN, it assumes the package name is foo.
+func importPathToNameBasic(importPath, srcDir string) (packageName string) {
+	base := path.Base(importPath)
+	if strings.HasPrefix(base, "v") {
+		if _, err := strconv.Atoi(base[1:]); err == nil {
+			dir := path.Dir(importPath)
+			if dir != "." {
+				return path.Base(dir)
+			}
+		}
+	}
+	return base
+}
+
+// importPathToNameGoPath finds out the actual package name, as declared in its .go files.
+// If there's a problem, it falls back to using importPathToNameBasic.
+func importPathToNameGoPath(importPath, srcDir string) (packageName string) {
+	// Fast path for standard library without going to disk.
+	if pkg, ok := stdImportPackage[importPath]; ok {
+		return pkg
+	}
+
+	pkgName, err := importPathToNameGoPathParse(importPath, srcDir)
+	if Debug {
+		log.Printf("importPathToNameGoPathParse(%q, srcDir=%q) = %q, %v", importPath, srcDir, pkgName, err)
+	}
+	if err == nil {
+		return pkgName
+	}
+	return importPathToNameBasic(importPath, srcDir)
+}
+
+// importPathToNameGoPathParse is a faster version of build.Import if
+// the only thing desired is the package name. It uses build.FindOnly
+// to find the directory and then only parses one file in the package,
+// trusting that the files in the directory are consistent.
+func importPathToNameGoPathParse(importPath, srcDir string) (packageName string, err error) {
+	buildPkg, err := build.Import(importPath, srcDir, build.FindOnly)
+	if err != nil {
+		return "", err
+	}
+	d, err := os.Open(buildPkg.Dir)
+	if err != nil {
+		return "", err
+	}
+	names, err := d.Readdirnames(-1)
+	d.Close()
+	if err != nil {
+		return "", err
+	}
+	sort.Strings(names) // to have predictable behavior
+	var lastErr error
+	var nfile int
+	for _, name := range names {
+		if !strings.HasSuffix(name, ".go") {
+			continue
+		}
+		if strings.HasSuffix(name, "_test.go") {
+			continue
+		}
+		nfile++
+		fullFile := filepath.Join(buildPkg.Dir, name)
+
+		fset := token.NewFileSet()
+		f, err := parser.ParseFile(fset, fullFile, nil, parser.PackageClauseOnly)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		pkgName := f.Name.Name
+		if pkgName == "documentation" {
+			// Special case from go/build.ImportDir, not
+			// handled by ctx.MatchFile.
+			continue
+		}
+		if pkgName == "main" {
+			// Also skip package main, assuming it's a +build ignore generator or example.
+			// Since you can't import a package main anyway, there's no harm here.
+			continue
+		}
+		return pkgName, nil
+	}
+	if lastErr != nil {
+		return "", lastErr
+	}
+	return "", fmt.Errorf("no importable package found in %d Go files", nfile)
+}
+
+var stdImportPackage = map[string]string{} // "net/http" => "http"
+
+func init() {
+	// Nothing in the standard library has a package name not
+	// matching its import base name.
+	for _, pkg := range stdlib {
+		if _, ok := stdImportPackage[pkg]; !ok {
+			stdImportPackage[pkg] = path.Base(pkg)
+		}
+	}
+}
+
+// Directory-scanning state.
+var (
+	// scanOnce guards calling scanGoDirs and assigning dirScan
+	scanOnce sync.Once
+	dirScan  map[string]*pkg // abs dir path => *pkg
+)
+
+type pkg struct {
+	dir             string // absolute file path to pkg directory ("/usr/lib/go/src/net/http")
+	importPath      string // full pkg import path ("net/http", "foo/bar/vendor/a/b")
+	importPathShort string // vendorless import path ("net/http", "a/b")
+}
+
+type pkgDistance struct {
+	pkg      *pkg
+	distance int // relative distance to target
+}
+
+// byDistanceOrImportPathShortLength sorts by relative distance breaking ties
+// on the short import path length and then the import string itself.
+type byDistanceOrImportPathShortLength []pkgDistance
+
+func (s byDistanceOrImportPathShortLength) Len() int { return len(s) }
+func (s byDistanceOrImportPathShortLength) Less(i, j int) bool {
+	di, dj := s[i].distance, s[j].distance
+	if di == -1 {
+		return false
+	}
+	if dj == -1 {
+		return true
+	}
+	if di != dj {
+		return di < dj
+	}
+
+	vi, vj := s[i].pkg.importPathShort, s[j].pkg.importPathShort
+	if len(vi) != len(vj) {
+		return len(vi) < len(vj)
+	}
+	return vi < vj
+}
+func (s byDistanceOrImportPathShortLength) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+func distance(basepath, targetpath string) int {
+	p, err := filepath.Rel(basepath, targetpath)
+	if err != nil {
+		return -1
+	}
+	if p == "." {
+		return 0
+	}
+	return strings.Count(p, string(filepath.Separator)) + 1
+}
+
+// scanGoDirs populates the dirScan map for GOPATH and GOROOT.
+func scanGoDirs() map[string]*pkg {
+	result := make(map[string]*pkg)
+	var mu sync.Mutex
+
+	add := func(root gopathwalk.Root, dir string) {
+		mu.Lock()
+		defer mu.Unlock()
+
+		if _, dup := result[dir]; dup {
+			return
+		}
+		importpath := filepath.ToSlash(dir[len(root.Path)+len("/"):])
+		result[dir] = &pkg{
+			importPath:      importpath,
+			importPathShort: VendorlessPath(importpath),
+			dir:             dir,
+		}
+	}
+	gopathwalk.Walk(gopathwalk.SrcDirsRoots(), add, gopathwalk.Options{Debug: Debug, ModulesEnabled: false})
+	return result
+}
+
+// VendorlessPath returns the devendorized version of the import path ipath.
+// For example, VendorlessPath("foo/bar/vendor/a/b") returns "a/b".
+func VendorlessPath(ipath string) string {
+	// Devendorize for use in import statement.
+	if i := strings.LastIndex(ipath, "/vendor/"); i >= 0 {
+		return ipath[i+len("/vendor/"):]
+	}
+	if strings.HasPrefix(ipath, "vendor/") {
+		return ipath[len("vendor/"):]
+	}
+	return ipath
+}
+
+// loadExports returns the set of exported symbols in the package at dir.
+// It returns nil on error or if the package name in dir does not match expectPackage.
+var loadExports func(ctx context.Context, expectPackage, dir string) (map[string]bool, error) = loadExportsGoPath
+
+func loadExportsGoPath(ctx context.Context, expectPackage, dir string) (map[string]bool, error) {
+	if Debug {
+		log.Printf("loading exports in dir %s (seeking package %s)", dir, expectPackage)
+	}
+	exports := make(map[string]bool)
+
+	buildCtx := build.Default
+
+	// ReadDir is like ioutil.ReadDir, but only returns *.go files
+	// and filters out _test.go files since they're not relevant
+	// and only slow things down.
+	buildCtx.ReadDir = func(dir string) (notTests []os.FileInfo, err error) {
+		all, err := ioutil.ReadDir(dir)
+		if err != nil {
+			return nil, err
+		}
+		notTests = all[:0]
+		for _, fi := range all {
+			name := fi.Name()
+			if strings.HasSuffix(name, ".go") && !strings.HasSuffix(name, "_test.go") {
+				notTests = append(notTests, fi)
+			}
+		}
+		return notTests, nil
+	}
+
+	files, err := buildCtx.ReadDir(dir)
+	if err != nil {
+		log.Print(err)
+		return nil, err
+	}
+
+	fset := token.NewFileSet()
+
+	for _, fi := range files {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+
+		match, err := buildCtx.MatchFile(dir, fi.Name())
+		if err != nil || !match {
+			continue
+		}
+		fullFile := filepath.Join(dir, fi.Name())
+		f, err := parser.ParseFile(fset, fullFile, nil, 0)
+		if err != nil {
+			if Debug {
+				log.Printf("Parsing %s: %v", fullFile, err)
+			}
+			return nil, err
+		}
+		pkgName := f.Name.Name
+		if pkgName == "documentation" {
+			// Special case from go/build.ImportDir, not
+			// handled by buildCtx.MatchFile.
+			continue
+		}
+		if pkgName != expectPackage {
+			err := fmt.Errorf("scan of dir %v is not expected package %v (actually %v)", dir, expectPackage, pkgName)
+			if Debug {
+				log.Print(err)
+			}
+			return nil, err
+		}
+		for name := range f.Scope.Objects {
+			if ast.IsExported(name) {
+				exports[name] = true
+			}
+		}
+	}
+
+	if Debug {
+		exportList := make([]string, 0, len(exports))
+		for k := range exports {
+			exportList = append(exportList, k)
+		}
+		sort.Strings(exportList)
+		log.Printf("loaded exports in dir %v (package %v): %v", dir, expectPackage, strings.Join(exportList, ", "))
+	}
+	return exports, nil
+}
+
+// findImport searches for a package with the given symbols.
+// If no package is found, findImport returns ("", false, nil)
+//
+// This is declared as a variable rather than a function so goimports
+// can be easily extended by adding a file with an init function.
+//
+// The rename value tells goimports whether to use the package name as
+// a local qualifier in an import. For example, if findImports("pkg",
+// "X") returns ("foo/bar", rename=true), then goimports adds the
+// import line:
+// 	import pkg "foo/bar"
+// to satisfy uses of pkg.X in the file.
+var findImport func(ctx context.Context, pkgName string, symbols map[string]bool, filename string) (foundPkg string, rename bool, err error) = findImportGoPath
+
+// findImportGoPath is the normal implementation of findImport.
+// (Some companies have their own internally.)
+func findImportGoPath(ctx context.Context, pkgName string, symbols map[string]bool, filename string) (foundPkg string, rename bool, err error) {
+	pkgDir, err := filepath.Abs(filename)
+	if err != nil {
+		return "", false, err
+	}
+	pkgDir = filepath.Dir(pkgDir)
+
+	// Fast path for the standard library.
+	// In the common case we hopefully never have to scan the GOPATH, which can
+	// be slow with moving disks.
+	if pkg, ok := findImportStdlib(pkgName, symbols); ok {
+		return pkg, false, nil
+	}
+	if pkgName == "rand" && symbols["Read"] {
+		// Special-case rand.Read.
+		//
+		// If findImportStdlib didn't find it above, don't go
+		// searching for it, lest it find and pick math/rand
+		// in GOROOT (new as of Go 1.6)
+		//
+		// crypto/rand is the safer choice.
+		return "", false, nil
+	}
+
+	// TODO(sameer): look at the import lines for other Go files in the
+	// local directory, since the user is likely to import the same packages
+	// in the current Go file.  Return rename=true when the other Go files
+	// use a renamed package that's also used in the current file.
+
+	// Scan $GOROOT and each $GOPATH.
+	scanOnce.Do(func() { dirScan = scanGoDirs() })
+
+	// Find candidate packages, looking only at their directory names first.
+	var candidates []pkgDistance
+	for _, pkg := range dirScan {
+		if pkgIsCandidate(filename, pkgName, pkg) {
+			candidates = append(candidates, pkgDistance{
+				pkg:      pkg,
+				distance: distance(pkgDir, pkg.dir),
+			})
+		}
+	}
+
+	// Sort the candidates by their import package length,
+	// assuming that shorter package names are better than long
+	// ones.  Note that this sorts by the de-vendored name, so
+	// there's no "penalty" for vendoring.
+	sort.Sort(byDistanceOrImportPathShortLength(candidates))
+	if Debug {
+		for i, c := range candidates {
+			log.Printf("%s candidate %d/%d: %v in %v", pkgName, i+1, len(candidates), c.pkg.importPathShort, c.pkg.dir)
+		}
+	}
+
+	// Collect exports for packages with matching names.
+
+	rescv := make([]chan *pkg, len(candidates))
+	for i := range candidates {
+		rescv[i] = make(chan *pkg, 1)
+	}
+	const maxConcurrentPackageImport = 4
+	loadExportsSem := make(chan struct{}, maxConcurrentPackageImport)
+
+	ctx, cancel := context.WithCancel(ctx)
+	var wg sync.WaitGroup
+	defer func() {
+		cancel()
+		wg.Wait()
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for i, c := range candidates {
+			select {
+			case loadExportsSem <- struct{}{}:
+			case <-ctx.Done():
+				return
+			}
+
+			wg.Add(1)
+			go func(c pkgDistance, resc chan<- *pkg) {
+				defer func() {
+					<-loadExportsSem
+					wg.Done()
+				}()
+
+				exports, err := loadExports(ctx, pkgName, c.pkg.dir)
+				if err != nil {
+					resc <- nil
+					return
+				}
+
+				// If it doesn't have the right
+				// symbols, send nil to mean no match.
+				for symbol := range symbols {
+					if !exports[symbol] {
+						resc <- nil
+						return
+					}
+				}
+				resc <- c.pkg
+			}(c, rescv[i])
+		}
+	}()
+
+	for _, resc := range rescv {
+		pkg := <-resc
+		if pkg == nil {
+			continue
+		}
+		// If the package name in the source doesn't match the import path's base,
+		// return true so the rewriter adds a name (import foo "github.com/bar/go-foo")
+		needsRename := path.Base(pkg.importPath) != pkgName
+		return pkg.importPathShort, needsRename, nil
+	}
+	return "", false, nil
+}
+
+// pkgIsCandidate reports whether pkg is a candidate for satisfying the
+// finding which package pkgIdent in the file named by filename is trying
+// to refer to.
+//
+// This check is purely lexical and is meant to be as fast as possible
+// because it's run over all $GOPATH directories to filter out poor
+// candidates in order to limit the CPU and I/O later parsing the
+// exports in candidate packages.
+//
+// filename is the file being formatted.
+// pkgIdent is the package being searched for, like "client" (if
+// searching for "client.New")
+func pkgIsCandidate(filename, pkgIdent string, pkg *pkg) bool {
+	// Check "internal" and "vendor" visibility:
+	if !canUse(filename, pkg.dir) {
+		return false
+	}
+
+	// Speed optimization to minimize disk I/O:
+	// the last two components on disk must contain the
+	// package name somewhere.
+	//
+	// This permits mismatch naming like directory
+	// "go-foo" being package "foo", or "pkg.v3" being "pkg",
+	// or directory "google.golang.org/api/cloudbilling/v1"
+	// being package "cloudbilling", but doesn't
+	// permit a directory "foo" to be package
+	// "bar", which is strongly discouraged
+	// anyway. There's no reason goimports needs
+	// to be slow just to accommodate that.
+	lastTwo := lastTwoComponents(pkg.importPathShort)
+	if strings.Contains(lastTwo, pkgIdent) {
+		return true
+	}
+	if hasHyphenOrUpperASCII(lastTwo) && !hasHyphenOrUpperASCII(pkgIdent) {
+		lastTwo = lowerASCIIAndRemoveHyphen(lastTwo)
+		if strings.Contains(lastTwo, pkgIdent) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func hasHyphenOrUpperASCII(s string) bool {
+	for i := 0; i < len(s); i++ {
+		b := s[i]
+		if b == '-' || ('A' <= b && b <= 'Z') {
+			return true
+		}
+	}
+	return false
+}
+
+func lowerASCIIAndRemoveHyphen(s string) (ret string) {
+	buf := make([]byte, 0, len(s))
+	for i := 0; i < len(s); i++ {
+		b := s[i]
+		switch {
+		case b == '-':
+			continue
+		case 'A' <= b && b <= 'Z':
+			buf = append(buf, b+('a'-'A'))
+		default:
+			buf = append(buf, b)
+		}
+	}
+	return string(buf)
+}
+
+// canUse reports whether the package in dir is usable from filename,
+// respecting the Go "internal" and "vendor" visibility rules.
+func canUse(filename, dir string) bool {
+	// Fast path check, before any allocations. If it doesn't contain vendor
+	// or internal, it's not tricky:
+	// Note that this can false-negative on directories like "notinternal",
+	// but we check it correctly below. This is just a fast path.
+	if !strings.Contains(dir, "vendor") && !strings.Contains(dir, "internal") {
+		return true
+	}
+
+	dirSlash := filepath.ToSlash(dir)
+	if !strings.Contains(dirSlash, "/vendor/") && !strings.Contains(dirSlash, "/internal/") && !strings.HasSuffix(dirSlash, "/internal") {
+		return true
+	}
+	// Vendor or internal directory only visible from children of parent.
+	// That means the path from the current directory to the target directory
+	// can contain ../vendor or ../internal but not ../foo/vendor or ../foo/internal
+	// or bar/vendor or bar/internal.
+	// After stripping all the leading ../, the only okay place to see vendor or internal
+	// is at the very beginning of the path.
+	absfile, err := filepath.Abs(filename)
+	if err != nil {
+		return false
+	}
+	absdir, err := filepath.Abs(dir)
+	if err != nil {
+		return false
+	}
+	rel, err := filepath.Rel(absfile, absdir)
+	if err != nil {
+		return false
+	}
+	relSlash := filepath.ToSlash(rel)
+	if i := strings.LastIndex(relSlash, "../"); i >= 0 {
+		relSlash = relSlash[i+len("../"):]
+	}
+	return !strings.Contains(relSlash, "/vendor/") && !strings.Contains(relSlash, "/internal/") && !strings.HasSuffix(relSlash, "/internal")
+}
+
+// lastTwoComponents returns at most the last two path components
+// of v, using either / or \ as the path separator.
+func lastTwoComponents(v string) string {
+	nslash := 0
+	for i := len(v) - 1; i >= 0; i-- {
+		if v[i] == '/' || v[i] == '\\' {
+			nslash++
+			if nslash == 2 {
+				return v[i:]
+			}
+		}
+	}
+	return v
+}
+
+type visitFn func(node ast.Node) ast.Visitor
+
+func (fn visitFn) Visit(node ast.Node) ast.Visitor {
+	return fn(node)
+}
+
+func findImportStdlib(shortPkg string, symbols map[string]bool) (importPath string, ok bool) {
+	for symbol := range symbols {
+		key := shortPkg + "." + symbol
+		path := stdlib[key]
+		if path == "" {
+			if key == "rand.Read" {
+				continue
+			}
+			return "", false
+		}
+		if importPath != "" && importPath != path {
+			// Ambiguous. Symbols pointed to different things.
+			return "", false
+		}
+		importPath = path
+	}
+	if importPath == "" && shortPkg == "rand" && symbols["Read"] {
+		return "crypto/rand", true
+	}
+	return importPath, importPath != ""
+}