Update vendored dependencies

vendor/golang.org/x/tools/internal/gopathwalk/walk.go

@@ -16,6 +16,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"time"
 
 	"golang.org/x/tools/internal/fastwalk"
 )
@@ -83,8 +84,9 @@ func walkDir(root Root, add func(Root, string), skip func(root Root, dir string)
 		}
 		return
 	}
+	start := time.Now()
 	if opts.Debug {
-		log.Printf("scanning %s", root.Path)
+		log.Printf("gopathwalk: scanning %s", root.Path)
 	}
 	w := &walker{
 		root: root,
@@ -98,7 +100,7 @@ func walkDir(root Root, add func(Root, string), skip func(root Root, dir string)
 	}
 
 	if opts.Debug {
-		log.Printf("scanned %s", root.Path)
+		log.Printf("gopathwalk: scanned %s in %v", root.Path, time.Since(start))
 	}
 }
 

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

@@ -17,6 +17,7 @@ import (
 	"os/exec"
 	"path"
 	"path/filepath"
+	"reflect"
 	"sort"
 	"strconv"
 	"strings"
@@ -475,9 +476,9 @@ func (p *pass) assumeSiblingImportsValid() {
 		}
 		for left, rights := range refs {
 			if imp, ok := importsByName[left]; ok {
-				if _, ok := stdlib[imp.ImportPath]; ok {
+				if m, ok := stdlib[imp.ImportPath]; ok {
 					// We have the stdlib in memory; no need to guess.
-					rights = stdlib[imp.ImportPath]
+					rights = copyExports(m)
 				}
 				p.addCandidate(imp, &packageInfo{
 					// no name; we already know it.
@@ -584,29 +585,133 @@ func getFixes(fset *token.FileSet, f *ast.File, filename string, env *ProcessEnv
 	return fixes, nil
 }
 
+// getCandidatePkgs returns the list of pkgs that are accessible from filename,
+// optionall filtered to only packages named pkgName.
+func getCandidatePkgs(pkgName, filename string, env *ProcessEnv) ([]*pkg, error) {
+	// TODO(heschi): filter out current package. (Don't forget x_test can import x.)
+
+	var result []*pkg
+	// Start off with the standard library.
+	for importPath := range stdlib {
+		if pkgName != "" && path.Base(importPath) != pkgName {
+			continue
+		}
+		result = append(result, &pkg{
+			dir:             filepath.Join(env.GOROOT, "src", importPath),
+			importPathShort: importPath,
+			packageName:     path.Base(importPath),
+			relevance:       0,
+		})
+	}
+
+	// Exclude goroot results -- getting them is relatively expensive, not cached,
+	// and generally redundant with the in-memory version.
+	exclude := []gopathwalk.RootType{gopathwalk.RootGOROOT}
+	// Only the go/packages resolver uses the first argument, and nobody uses that resolver.
+	scannedPkgs, err := env.GetResolver().scan(nil, true, exclude)
+	if err != nil {
+		return nil, err
+	}
+
+	dupCheck := map[string]struct{}{}
+	for _, pkg := range scannedPkgs {
+		if pkgName != "" && pkg.packageName != pkgName {
+			continue
+		}
+		if !canUse(filename, pkg.dir) {
+			continue
+		}
+		if _, ok := dupCheck[pkg.importPathShort]; ok {
+			continue
+		}
+		dupCheck[pkg.importPathShort] = struct{}{}
+		result = append(result, pkg)
+	}
+
+	// Sort first by relevance, then by package name, with import path as a tiebreaker.
+	sort.Slice(result, func(i, j int) bool {
+		pi, pj := result[i], result[j]
+		if pi.relevance != pj.relevance {
+			return pi.relevance < pj.relevance
+		}
+		if pi.packageName != pj.packageName {
+			return pi.packageName < pj.packageName
+		}
+		return pi.importPathShort < pj.importPathShort
+	})
+
+	return result, nil
+}
+
+func candidateImportName(pkg *pkg) string {
+	if importPathToAssumedName(pkg.importPathShort) != pkg.packageName {
+		return pkg.packageName
+	}
+	return ""
+}
+
 // getAllCandidates gets all of the candidates to be imported, regardless of if they are needed.
 func getAllCandidates(filename string, env *ProcessEnv) ([]ImportFix, error) {
-	// TODO(suzmue): scan for additional candidates and filter out
-	// current package.
-
-	// Get the stdlib candidates and sort by import path.
-	var paths []string
-	for importPath := range stdlib {
-		paths = append(paths, importPath)
+	pkgs, err := getCandidatePkgs("", filename, env)
+	if err != nil {
+		return nil, err
 	}
-	sort.Strings(paths)
-
-	var imports []ImportFix
-	for _, importPath := range paths {
-		imports = append(imports, ImportFix{
+	result := make([]ImportFix, 0, len(pkgs))
+	for _, pkg := range pkgs {
+		result = append(result, ImportFix{
 			StmtInfo: ImportInfo{
-				ImportPath: importPath,
+				ImportPath: pkg.importPathShort,
+				Name:       candidateImportName(pkg),
 			},
-			IdentName: path.Base(importPath),
+			IdentName: pkg.packageName,
 			FixType:   AddImport,
 		})
 	}
-	return imports, nil
+	return result, nil
+}
+
+// A PackageExport is a package and its exports.
+type PackageExport struct {
+	Fix     *ImportFix
+	Exports []string
+}
+
+func getPackageExports(completePackage, filename string, env *ProcessEnv) ([]PackageExport, error) {
+	pkgs, err := getCandidatePkgs(completePackage, filename, env)
+	if err != nil {
+		return nil, err
+	}
+
+	results := make([]PackageExport, 0, len(pkgs))
+	for _, pkg := range pkgs {
+		fix := &ImportFix{
+			StmtInfo: ImportInfo{
+				ImportPath: pkg.importPathShort,
+				Name:       candidateImportName(pkg),
+			},
+			IdentName: pkg.packageName,
+			FixType:   AddImport,
+		}
+		var exports []string
+		if e, ok := stdlib[pkg.importPathShort]; ok {
+			exports = e
+		} else {
+			exports, err = loadExportsForPackage(context.Background(), env, completePackage, pkg)
+			if err != nil {
+				if env.Debug {
+					env.Logf("while completing %q, error loading exports from %q: %v", completePackage, pkg.importPathShort, err)
+				}
+				continue
+			}
+		}
+		sort.Strings(exports)
+		results = append(results, PackageExport{
+			Fix:     fix,
+			Exports: exports,
+		})
+	}
+
+	return results, nil
 }
 
 // ProcessEnv contains environment variables and settings that affect the use of
@@ -678,6 +783,13 @@ func (e *ProcessEnv) buildContext() *build.Context {
 	ctx := build.Default
 	ctx.GOROOT = e.GOROOT
 	ctx.GOPATH = e.GOPATH
+
+	// As of Go 1.14, build.Context has a WorkingDir field
+	// (see golang.org/issue/34860).
+	// Populate it only if present.
+	if wd := reflect.ValueOf(&ctx).Elem().FieldByName("WorkingDir"); wd.IsValid() && wd.Kind() == reflect.String {
+		wd.SetString(e.WorkingDir)
+	}
 	return &ctx
 }
 
@@ -712,9 +824,10 @@ func cmdDebugStr(cmd *exec.Cmd) string {
 
 func addStdlibCandidates(pass *pass, refs references) {
 	add := func(pkg string) {
+		exports := copyExports(stdlib[pkg])
 		pass.addCandidate(
 			&ImportInfo{ImportPath: pkg},
-			&packageInfo{name: path.Base(pkg), exports: stdlib[pkg]})
+			&packageInfo{name: path.Base(pkg), exports: exports})
 	}
 	for left := range refs {
 		if left == "rand" {
@@ -735,12 +848,15 @@ func addStdlibCandidates(pass *pass, refs references) {
 type Resolver interface {
 	// loadPackageNames loads the package names in importPaths.
 	loadPackageNames(importPaths []string, srcDir string) (map[string]string, error)
-	// scan finds (at least) the packages satisfying refs. The returned slice is unordered.
-	scan(refs references) ([]*pkg, error)
+	// scan finds (at least) the packages satisfying refs. If loadNames is true,
+	// package names will be set on the results, and dirs whose package name
+	// could not be determined will be excluded.
+	scan(refs references, loadNames bool, exclude []gopathwalk.RootType) ([]*pkg, error)
 	// loadExports returns the set of exported symbols in the package at dir.
-	// It returns an error if the package name in dir does not match expectPackage.
 	// loadExports may be called concurrently.
-	loadExports(ctx context.Context, expectPackage string, pkg *pkg) (map[string]bool, error)
+	loadExports(ctx context.Context, pkg *pkg) (string, []string, error)
+
+	ClearForNewScan()
 }
 
 // gopackagesResolver implements resolver for GOPATH and module workspaces using go/packages.
@@ -748,6 +864,8 @@ type goPackagesResolver struct {
 	env *ProcessEnv
 }
 
+func (r *goPackagesResolver) ClearForNewScan() {}
+
 func (r *goPackagesResolver) loadPackageNames(importPaths []string, srcDir string) (map[string]string, error) {
 	if len(importPaths) == 0 {
 		return nil, nil
@@ -772,7 +890,7 @@ func (r *goPackagesResolver) loadPackageNames(importPaths []string, srcDir strin
 
 }
 
-func (r *goPackagesResolver) scan(refs references) ([]*pkg, error) {
+func (r *goPackagesResolver) scan(refs references, _ bool, _ []gopathwalk.RootType) ([]*pkg, error) {
 	var loadQueries []string
 	for pkgName := range refs {
 		loadQueries = append(loadQueries, "iamashamedtousethedisabledqueryname="+pkgName)
@@ -790,33 +908,34 @@ func (r *goPackagesResolver) scan(refs references) ([]*pkg, error) {
 			dir:             filepath.Dir(goPackage.CompiledGoFiles[0]),
 			importPathShort: VendorlessPath(goPackage.PkgPath),
 			goPackage:       goPackage,
+			packageName:     goPackage.Name,
 		})
 	}
 	return scan, nil
 }
 
-func (r *goPackagesResolver) loadExports(ctx context.Context, expectPackage string, pkg *pkg) (map[string]bool, error) {
+func (r *goPackagesResolver) loadExports(ctx context.Context, pkg *pkg) (string, []string, error) {
 	if pkg.goPackage == nil {
-		return nil, fmt.Errorf("goPackage not set")
+		return "", nil, fmt.Errorf("goPackage not set")
 	}
-	exports := map[string]bool{}
+	var exports []string
 	fset := token.NewFileSet()
 	for _, fname := range pkg.goPackage.CompiledGoFiles {
 		f, err := parser.ParseFile(fset, fname, nil, 0)
 		if err != nil {
-			return nil, fmt.Errorf("parsing %s: %v", fname, err)
+			return "", nil, fmt.Errorf("parsing %s: %v", fname, err)
 		}
 		for name := range f.Scope.Objects {
 			if ast.IsExported(name) {
-				exports[name] = true
+				exports = append(exports, name)
 			}
 		}
 	}
-	return exports, nil
+	return pkg.goPackage.Name, exports, nil
 }
 
 func addExternalCandidates(pass *pass, refs references, filename string) error {
-	dirScan, err := pass.env.GetResolver().scan(refs)
+	dirScan, err := pass.env.GetResolver().scan(refs, false, nil)
 	if err != nil {
 		return err
 	}
@@ -914,10 +1033,24 @@ func importPathToAssumedName(importPath string) string {
 
 // gopathResolver implements resolver for GOPATH workspaces.
 type gopathResolver struct {
-	env *ProcessEnv
+	env   *ProcessEnv
+	cache *dirInfoCache
+}
+
+func (r *gopathResolver) init() {
+	if r.cache == nil {
+		r.cache = &dirInfoCache{
+			dirs: map[string]*directoryPackageInfo{},
+		}
+	}
+}
+
+func (r *gopathResolver) ClearForNewScan() {
+	r.cache = nil
 }
 
 func (r *gopathResolver) loadPackageNames(importPaths []string, srcDir string) (map[string]string, error) {
+	r.init()
 	names := map[string]string{}
 	for _, path := range importPaths {
 		names[path] = importPathToName(r.env, path, srcDir)
@@ -1000,6 +1133,8 @@ type pkg struct {
 	goPackage       *packages.Package
 	dir             string // absolute file path to pkg directory ("/usr/lib/go/src/net/http")
 	importPathShort string // vendorless import path ("net/http", "a/b")
+	packageName     string // package name loaded from source if requested
+	relevance       int    // a weakly-defined score of how relevant a package is. 0 is most relevant.
 }
 
 type pkgDistance struct {
@@ -1043,32 +1178,74 @@ func distance(basepath, targetpath string) int {
 	return strings.Count(p, string(filepath.Separator)) + 1
 }
 
-func (r *gopathResolver) scan(_ references) ([]*pkg, error) {
-	dupCheck := make(map[string]bool)
-	var result []*pkg
-
-	var mu sync.Mutex
-
+func (r *gopathResolver) scan(_ references, loadNames bool, exclude []gopathwalk.RootType) ([]*pkg, error) {
+	r.init()
 	add := func(root gopathwalk.Root, dir string) {
-		mu.Lock()
-		defer mu.Unlock()
-
-		if _, dup := dupCheck[dir]; dup {
+		// We assume cached directories have not changed. We can skip them and their
+		// children.
+		if _, ok := r.cache.Load(dir); ok {
 			return
 		}
-		dupCheck[dir] = true
+
 		importpath := filepath.ToSlash(dir[len(root.Path)+len("/"):])
-		result = append(result, &pkg{
-			importPathShort: VendorlessPath(importpath),
-			dir:             dir,
-		})
+		info := directoryPackageInfo{
+			status:                 directoryScanned,
+			dir:                    dir,
+			rootType:               root.Type,
+			nonCanonicalImportPath: VendorlessPath(importpath),
+		}
+		r.cache.Store(dir, info)
+	}
+	roots := filterRoots(gopathwalk.SrcDirsRoots(r.env.buildContext()), exclude)
+	gopathwalk.Walk(roots, add, gopathwalk.Options{Debug: r.env.Debug, ModulesEnabled: false})
+	var result []*pkg
+	for _, dir := range r.cache.Keys() {
+		info, ok := r.cache.Load(dir)
+		if !ok {
+			continue
+		}
+		if loadNames {
+			var err error
+			info, err = r.cache.CachePackageName(info)
+			if err != nil {
+				continue
+			}
+		}
+
+		p := &pkg{
+			importPathShort: info.nonCanonicalImportPath,
+			dir:             dir,
+			relevance:       1,
+			packageName:     info.packageName,
+		}
+		if info.rootType == gopathwalk.RootGOROOT {
+			p.relevance = 0
+		}
+		result = append(result, p)
 	}
-	gopathwalk.Walk(gopathwalk.SrcDirsRoots(r.env.buildContext()), add, gopathwalk.Options{Debug: r.env.Debug, ModulesEnabled: false})
 	return result, nil
 }
 
-func (r *gopathResolver) loadExports(ctx context.Context, expectPackage string, pkg *pkg) (map[string]bool, error) {
-	return loadExportsFromFiles(ctx, r.env, expectPackage, pkg.dir)
+func filterRoots(roots []gopathwalk.Root, exclude []gopathwalk.RootType) []gopathwalk.Root {
+	var result []gopathwalk.Root
+outer:
+	for _, root := range roots {
+		for _, i := range exclude {
+			if i == root.Type {
+				continue outer
+			}
+		}
+		result = append(result, root)
+	}
+	return result
+}
+
+func (r *gopathResolver) loadExports(ctx context.Context, pkg *pkg) (string, []string, error) {
+	r.init()
+	if info, ok := r.cache.Load(pkg.dir); ok {
+		return r.cache.CacheExports(ctx, r.env, info)
+	}
+	return loadExportsFromFiles(ctx, r.env, pkg.dir)
 }
 
 // VendorlessPath returns the devendorized version of the import path ipath.
@@ -1084,13 +1261,13 @@ func VendorlessPath(ipath string) string {
 	return ipath
 }
 
-func loadExportsFromFiles(ctx context.Context, env *ProcessEnv, expectPackage string, dir string) (map[string]bool, error) {
-	exports := make(map[string]bool)
+func loadExportsFromFiles(ctx context.Context, env *ProcessEnv, dir string) (string, []string, error) {
+	var exports []string
 
 	// Look for non-test, buildable .go files which could provide exports.
 	all, err := ioutil.ReadDir(dir)
 	if err != nil {
-		return nil, err
+		return "", nil, err
 	}
 	var files []os.FileInfo
 	for _, fi := range all {
@@ -1106,47 +1283,42 @@ func loadExportsFromFiles(ctx context.Context, env *ProcessEnv, expectPackage st
 	}
 
 	if len(files) == 0 {
-		return nil, fmt.Errorf("dir %v contains no buildable, non-test .go files", dir)
+		return "", nil, fmt.Errorf("dir %v contains no buildable, non-test .go files", dir)
 	}
 
+	var pkgName string
 	fset := token.NewFileSet()
 	for _, fi := range files {
 		select {
 		case <-ctx.Done():
-			return nil, ctx.Err()
+			return "", nil, ctx.Err()
 		default:
 		}
 
 		fullFile := filepath.Join(dir, fi.Name())
 		f, err := parser.ParseFile(fset, fullFile, nil, 0)
 		if err != nil {
-			return nil, fmt.Errorf("parsing %s: %v", fullFile, err)
+			return "", nil, fmt.Errorf("parsing %s: %v", fullFile, err)
 		}
-		pkgName := f.Name.Name
-		if pkgName == "documentation" {
+		if f.Name.Name == "documentation" {
 			// Special case from go/build.ImportDir, not
 			// handled by MatchFile above.
 			continue
 		}
-		if pkgName != expectPackage {
-			return nil, fmt.Errorf("scan of dir %v is not expected package %v (actually %v)", dir, expectPackage, pkgName)
-		}
+		pkgName = f.Name.Name
 		for name := range f.Scope.Objects {
 			if ast.IsExported(name) {
-				exports[name] = true
+				exports = append(exports, name)
 			}
 		}
 	}
 
 	if env.Debug {
-		exportList := make([]string, 0, len(exports))
-		for k := range exports {
-			exportList = append(exportList, k)
-		}
-		sort.Strings(exportList)
-		env.Logf("loaded exports in dir %v (package %v): %v", dir, expectPackage, strings.Join(exportList, ", "))
+		sortedExports := append([]string(nil), exports...)
+		sort.Strings(sortedExports)
+		env.Logf("loaded exports in dir %v (package %v): %v", dir, pkgName, strings.Join(sortedExports, ", "))
 	}
-	return exports, nil
+	return pkgName, exports, nil
 }
 
 // findImport searches for a package with the given symbols.
@@ -1221,7 +1393,7 @@ func findImport(ctx context.Context, pass *pass, dirScan []*pkg, pkgName string,
 				if pass.env.Debug {
 					pass.env.Logf("loading exports in dir %s (seeking package %s)", c.pkg.dir, pkgName)
 				}
-				exports, err := pass.env.GetResolver().loadExports(ctx, pkgName, c.pkg)
+				exports, err := loadExportsForPackage(ctx, pass.env, pkgName, c.pkg)
 				if err != nil {
 					if pass.env.Debug {
 						pass.env.Logf("loading exports in dir %s (seeking package %s): %v", c.pkg.dir, pkgName, err)
@@ -1230,10 +1402,15 @@ func findImport(ctx context.Context, pass *pass, dirScan []*pkg, pkgName string,
 					return
 				}
 
+				exportsMap := make(map[string]bool, len(exports))
+				for _, sym := range exports {
+					exportsMap[sym] = true
+				}
+
 				// If it doesn't have the right
 				// symbols, send nil to mean no match.
 				for symbol := range symbols {
-					if !exports[symbol] {
+					if !exportsMap[symbol] {
 						resc <- nil
 						return
 					}
@@ -1253,6 +1430,17 @@ func findImport(ctx context.Context, pass *pass, dirScan []*pkg, pkgName string,
 	return nil, nil
 }
 
+func loadExportsForPackage(ctx context.Context, env *ProcessEnv, expectPkg string, pkg *pkg) ([]string, error) {
+	pkgName, exports, err := env.GetResolver().loadExports(ctx, pkg)
+	if err != nil {
+		return nil, err
+	}
+	if expectPkg != pkgName {
+		return nil, fmt.Errorf("dir %v is package %v, wanted %v", pkg.dir, pkgName, expectPkg)
+	}
+	return exports, err
+}
+
 // 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.
@@ -1383,3 +1571,11 @@ type visitFn func(node ast.Node) ast.Visitor
 func (fn visitFn) Visit(node ast.Node) ast.Visitor {
 	return fn(node)
 }
+
+func copyExports(pkg []string) map[string]bool {
+	m := make(map[string]bool, len(pkg))
+	for _, v := range pkg {
+		m[v] = true
+	}
+	return m
+}

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

@@ -105,13 +105,22 @@ func ApplyFixes(fixes []*ImportFix, filename string, src []byte, opt *Options) (
 // GetAllCandidates gets all of the standard library candidate packages to import in
 // sorted order on import path.
 func GetAllCandidates(filename string, opt *Options) (pkgs []ImportFix, err error) {
-	_, opt, err = initialize(filename, []byte{}, opt)
+	_, opt, err = initialize(filename, nil, opt)
 	if err != nil {
 		return nil, err
 	}
 	return getAllCandidates(filename, opt.Env)
 }
 
+// GetPackageExports returns all known packages with name pkg and their exports.
+func GetPackageExports(pkg, filename string, opt *Options) (exports []PackageExport, err error) {
+	_, opt, err = initialize(filename, nil, opt)
+	if err != nil {
+		return nil, err
+	}
+	return getPackageExports(pkg, filename, opt.Env)
+}
+
 // initialize sets the values for opt and src.
 // If they are provided, they are not changed. Otherwise opt is set to the
 // default values and src is read from the file system.

vendor/golang.org/x/tools/internal/imports/mod.go

@@ -14,10 +14,10 @@ import (
 	"strconv"
 	"strings"
 	"sync"
-	"time"
 
 	"golang.org/x/tools/internal/gopathwalk"
 	"golang.org/x/tools/internal/module"
+	"golang.org/x/tools/internal/semver"
 )
 
 // ModuleResolver implements resolver for modules using the go command as little
@@ -25,38 +25,81 @@ import (
 type ModuleResolver struct {
 	env            *ProcessEnv
 	moduleCacheDir string
+	dummyVendorMod *ModuleJSON // If vendoring is enabled, the pseudo-module that represents the /vendor directory.
 
 	Initialized   bool
 	Main          *ModuleJSON
 	ModsByModPath []*ModuleJSON // All modules, ordered by # of path components in module Path...
 	ModsByDir     []*ModuleJSON // ...or Dir.
 
-	// moduleCacheInfo stores information about the module cache.
-	moduleCacheInfo *moduleCacheInfo
+	// moduleCacheCache stores information about the module cache.
+	moduleCacheCache *dirInfoCache
+	otherCache       *dirInfoCache
 }
 
 type ModuleJSON struct {
-	Path     string           // module path
-	Version  string           // module version
-	Versions []string         // available module versions (with -versions)
-	Replace  *ModuleJSON      // replaced by this module
-	Time     *time.Time       // time version was created
-	Update   *ModuleJSON      // available update, if any (with -u)
-	Main     bool             // is this the main module?
-	Indirect bool             // is this module only an indirect dependency of main module?
-	Dir      string           // directory holding files for this module, if any
-	GoMod    string           // path to go.mod file for this module, if any
-	Error    *ModuleErrorJSON // error loading module
-}
-
-type ModuleErrorJSON struct {
-	Err string // the error itself
+	Path      string      // module path
+	Replace   *ModuleJSON // replaced by this module
+	Main      bool        // is this the main module?
+	Dir       string      // directory holding files for this module, if any
+	GoMod     string      // path to go.mod file for this module, if any
+	GoVersion string      // go version used in module
 }
 
 func (r *ModuleResolver) init() error {
 	if r.Initialized {
 		return nil
 	}
+	mainMod, vendorEnabled, err := vendorEnabled(r.env)
+	if err != nil {
+		return err
+	}
+
+	if mainMod != nil && vendorEnabled {
+		// Vendor mode is on, so all the non-Main modules are irrelevant,
+		// and we need to search /vendor for everything.
+		r.Main = mainMod
+		r.dummyVendorMod = &ModuleJSON{
+			Path: "",
+			Dir:  filepath.Join(mainMod.Dir, "vendor"),
+		}
+		r.ModsByModPath = []*ModuleJSON{mainMod, r.dummyVendorMod}
+		r.ModsByDir = []*ModuleJSON{mainMod, r.dummyVendorMod}
+	} else {
+		// Vendor mode is off, so run go list -m ... to find everything.
+		r.initAllMods()
+	}
+
+	r.moduleCacheDir = filepath.Join(filepath.SplitList(r.env.GOPATH)[0], "/pkg/mod")
+
+	sort.Slice(r.ModsByModPath, func(i, j int) bool {
+		count := func(x int) int {
+			return strings.Count(r.ModsByModPath[x].Path, "/")
+		}
+		return count(j) < count(i) // descending order
+	})
+	sort.Slice(r.ModsByDir, func(i, j int) bool {
+		count := func(x int) int {
+			return strings.Count(r.ModsByDir[x].Dir, "/")
+		}
+		return count(j) < count(i) // descending order
+	})
+
+	if r.moduleCacheCache == nil {
+		r.moduleCacheCache = &dirInfoCache{
+			dirs: map[string]*directoryPackageInfo{},
+		}
+	}
+	if r.otherCache == nil {
+		r.otherCache = &dirInfoCache{
+			dirs: map[string]*directoryPackageInfo{},
+		}
+	}
+	r.Initialized = true
+	return nil
+}
+
+func (r *ModuleResolver) initAllMods() error {
 	stdout, err := r.env.invokeGo("list", "-m", "-json", "...")
 	if err != nil {
 		return err
@@ -79,30 +122,23 @@ func (r *ModuleResolver) init() error {
 			r.Main = mod
 		}
 	}
-
-	sort.Slice(r.ModsByModPath, func(i, j int) bool {
-		count := func(x int) int {
-			return strings.Count(r.ModsByModPath[x].Path, "/")
-		}
-		return count(j) < count(i) // descending order
-	})
-	sort.Slice(r.ModsByDir, func(i, j int) bool {
-		count := func(x int) int {
-			return strings.Count(r.ModsByDir[x].Dir, "/")
-		}
-		return count(j) < count(i) // descending order
-	})
-
-	if r.moduleCacheInfo == nil {
-		r.moduleCacheInfo = &moduleCacheInfo{
-			modCacheDirInfo: make(map[string]*directoryPackageInfo),
-		}
-	}
-
-	r.Initialized = true
 	return nil
 }
 
+func (r *ModuleResolver) ClearForNewScan() {
+	r.otherCache = &dirInfoCache{
+		dirs: map[string]*directoryPackageInfo{},
+	}
+}
+
+func (r *ModuleResolver) ClearForNewMod() {
+	env := r.env
+	*r = ModuleResolver{
+		env: env,
+	}
+	r.init()
+}
+
 // findPackage returns the module and directory that contains the package at
 // the given import path, or returns nil, "" if no module is in scope.
 func (r *ModuleResolver) findPackage(importPath string) (*ModuleJSON, string) {
@@ -118,22 +154,31 @@ func (r *ModuleResolver) findPackage(importPath string) (*ModuleJSON, string) {
 			continue
 		}
 
-		if info, ok := r.moduleCacheInfo.Load(pkgDir); ok {
-			if packageScanned, err := info.reachedStatus(directoryScanned); packageScanned {
+		if info, ok := r.cacheLoad(pkgDir); ok {
+			if loaded, err := info.reachedStatus(nameLoaded); loaded {
 				if err != nil {
-					// There was some error with scanning this directory.
-					// It does not contain a valid package.
-					continue
+					continue // No package in this dir.
 				}
 				return m, pkgDir
 			}
+			if scanned, err := info.reachedStatus(directoryScanned); scanned && err != nil {
+				continue // Dir is unreadable, etc.
+			}
+			// This is slightly wrong: a directory doesn't have to have an
+			// importable package to count as a package for package-to-module
+			// resolution. package main or _test files should count but
+			// don't.
+			// TODO(heschi): fix this.
+			if _, err := r.cachePackageName(info); err == nil {
+				return m, pkgDir
+			}
 		}
 
+		// Not cached. Read the filesystem.
 		pkgFiles, err := ioutil.ReadDir(pkgDir)
 		if err != nil {
 			continue
 		}
-
 		// A module only contains a package if it has buildable go
 		// files in that directory. If not, it could be provided by an
 		// outer module. See #29736.
@@ -146,6 +191,40 @@ func (r *ModuleResolver) findPackage(importPath string) (*ModuleJSON, string) {
 	return nil, ""
 }
 
+func (r *ModuleResolver) cacheLoad(dir string) (directoryPackageInfo, bool) {
+	if info, ok := r.moduleCacheCache.Load(dir); ok {
+		return info, ok
+	}
+	return r.otherCache.Load(dir)
+}
+
+func (r *ModuleResolver) cacheStore(info directoryPackageInfo) {
+	if info.rootType == gopathwalk.RootModuleCache {
+		r.moduleCacheCache.Store(info.dir, info)
+	} else {
+		r.otherCache.Store(info.dir, info)
+	}
+}
+
+func (r *ModuleResolver) cacheKeys() []string {
+	return append(r.moduleCacheCache.Keys(), r.otherCache.Keys()...)
+}
+
+// cachePackageName caches the package name for a dir already in the cache.
+func (r *ModuleResolver) cachePackageName(info directoryPackageInfo) (directoryPackageInfo, error) {
+	if info.rootType == gopathwalk.RootModuleCache {
+		return r.moduleCacheCache.CachePackageName(info)
+	}
+	return r.otherCache.CachePackageName(info)
+}
+
+func (r *ModuleResolver) cacheExports(ctx context.Context, env *ProcessEnv, info directoryPackageInfo) (string, []string, error) {
+	if info.rootType == gopathwalk.RootModuleCache {
+		return r.moduleCacheCache.CacheExports(ctx, env, info)
+	}
+	return r.otherCache.CacheExports(ctx, env, info)
+}
+
 // findModuleByDir returns the module that contains dir, or nil if no such
 // module is in scope.
 func (r *ModuleResolver) findModuleByDir(dir string) *ModuleJSON {
@@ -184,28 +263,45 @@ func (r *ModuleResolver) dirIsNestedModule(dir string, mod *ModuleJSON) bool {
 		// so it cannot be a nested module.
 		return false
 	}
-	mf := r.findModFile(dir)
-	if mf == "" {
+	if mod != nil && mod == r.dummyVendorMod {
+		// The /vendor pseudomodule is flattened and doesn't actually count.
 		return false
 	}
-	return filepath.Dir(mf) != mod.Dir
+	modDir, _ := r.modInfo(dir)
+	if modDir == "" {
+		return false
+	}
+	return modDir != mod.Dir
 }
 
-func (r *ModuleResolver) findModFile(dir string) string {
+func (r *ModuleResolver) modInfo(dir string) (modDir string, modName string) {
+	readModName := func(modFile string) string {
+		modBytes, err := ioutil.ReadFile(modFile)
+		if err != nil {
+			return ""
+		}
+		return modulePath(modBytes)
+	}
+
 	if r.dirInModuleCache(dir) {
 		matches := modCacheRegexp.FindStringSubmatch(dir)
 		index := strings.Index(dir, matches[1]+"@"+matches[2])
-		return filepath.Join(dir[:index], matches[1]+"@"+matches[2], "go.mod")
+		modDir := filepath.Join(dir[:index], matches[1]+"@"+matches[2])
+		return modDir, readModName(filepath.Join(modDir, "go.mod"))
 	}
 	for {
+		if info, ok := r.cacheLoad(dir); ok {
+			return info.moduleDir, info.moduleName
+		}
 		f := filepath.Join(dir, "go.mod")
 		info, err := os.Stat(f)
 		if err == nil && !info.IsDir() {
-			return f
+			return dir, readModName(f)
 		}
+
 		d := filepath.Dir(dir)
 		if len(d) >= len(dir) {
-			return "" // reached top of file system, no go.mod
+			return "", "" // reached top of file system, no go.mod
 		}
 		dir = d
 	}
@@ -237,7 +333,7 @@ func (r *ModuleResolver) loadPackageNames(importPaths []string, srcDir string) (
 	return names, nil
 }
 
-func (r *ModuleResolver) scan(_ references) ([]*pkg, error) {
+func (r *ModuleResolver) scan(_ references, loadNames bool, exclude []gopathwalk.RootType) ([]*pkg, error) {
 	if err := r.init(); err != nil {
 		return nil, err
 	}
@@ -249,35 +345,30 @@ func (r *ModuleResolver) scan(_ references) ([]*pkg, error) {
 	if r.Main != nil {
 		roots = append(roots, gopathwalk.Root{r.Main.Dir, gopathwalk.RootCurrentModule})
 	}
-	if r.moduleCacheDir == "" {
-		r.moduleCacheDir = filepath.Join(filepath.SplitList(r.env.GOPATH)[0], "/pkg/mod")
-	}
-	roots = append(roots, gopathwalk.Root{r.moduleCacheDir, gopathwalk.RootModuleCache})
-
-	// Walk replace targets, just in case they're not in any of the above.
-	for _, mod := range r.ModsByModPath {
-		if mod.Replace != nil {
-			roots = append(roots, gopathwalk.Root{mod.Dir, gopathwalk.RootOther})
+	if r.dummyVendorMod != nil {
+		roots = append(roots, gopathwalk.Root{r.dummyVendorMod.Dir, gopathwalk.RootOther})
+	} else {
+		roots = append(roots, gopathwalk.Root{r.moduleCacheDir, gopathwalk.RootModuleCache})
+		// Walk replace targets, just in case they're not in any of the above.
+		for _, mod := range r.ModsByModPath {
+			if mod.Replace != nil {
+				roots = append(roots, gopathwalk.Root{mod.Dir, gopathwalk.RootOther})
+			}
 		}
 	}
 
+	roots = filterRoots(roots, exclude)
+
 	var result []*pkg
-	dupCheck := make(map[string]bool)
 	var mu sync.Mutex
 
-	// Packages in the module cache are immutable. If we have
-	// already seen this package on a previous scan of the module
-	// cache, return that result.
+	// We assume cached directories have not changed. We can skip them and their
+	// children.
 	skip := func(root gopathwalk.Root, dir string) bool {
 		mu.Lock()
 		defer mu.Unlock()
-		// If we have already processed this directory on this walk, skip it.
-		if _, dup := dupCheck[dir]; dup {
-			return true
-		}
 
-		// If we have saved this directory information, skip it.
-		info, ok := r.moduleCacheInfo.Load(dir)
+		info, ok := r.cacheLoad(dir)
 		if !ok {
 			return false
 		}
@@ -288,44 +379,19 @@ func (r *ModuleResolver) scan(_ references) ([]*pkg, error) {
 		return packageScanned
 	}
 
+	// Add anything new to the cache. We'll process everything in it below.
 	add := func(root gopathwalk.Root, dir string) {
 		mu.Lock()
 		defer mu.Unlock()
-		if _, dup := dupCheck[dir]; dup {
-			return
-		}
 
-		info, err := r.scanDirForPackage(root, dir)
-		if err != nil {
-			return
-		}
-		if root.Type == gopathwalk.RootModuleCache {
-			// Save this package information in the cache and return.
-			// Packages from the module cache are added after Walk.
-			r.moduleCacheInfo.Store(dir, info)
-			return
-		}
-
-		// Skip this package if there was an error loading package info.
-		if info.err != nil {
-			return
-		}
-
-		// The rest of this function canonicalizes the packages using the results
-		// of initializing the resolver from 'go list -m'.
-		res, err := r.canonicalize(root.Type, info.nonCanonicalImportPath, info.dir, info.needsReplace)
-		if err != nil {
-			return
-		}
-
-		result = append(result, res)
+		r.cacheStore(r.scanDirForPackage(root, dir))
 	}
 
 	gopathwalk.WalkSkip(roots, add, skip, gopathwalk.Options{Debug: r.env.Debug, ModulesEnabled: true})
 
-	// Add the packages from the modules in the mod cache that were skipped.
-	for _, dir := range r.moduleCacheInfo.Keys() {
-		info, ok := r.moduleCacheInfo.Load(dir)
+	// Everything we already had, and everything new, is now in the cache.
+	for _, dir := range r.cacheKeys() {
+		info, ok := r.cacheLoad(dir)
 		if !ok {
 			continue
 		}
@@ -335,7 +401,15 @@ func (r *ModuleResolver) scan(_ references) ([]*pkg, error) {
 			continue
 		}
 
-		res, err := r.canonicalize(gopathwalk.RootModuleCache, info.nonCanonicalImportPath, info.dir, info.needsReplace)
+		// If we want package names, make sure the cache has them.
+		if loadNames {
+			var err error
+			if info, err = r.cachePackageName(info); err != nil {
+				continue
+			}
+		}
+
+		res, err := r.canonicalize(info)
 		if err != nil {
 			continue
 		}
@@ -347,60 +421,70 @@ func (r *ModuleResolver) scan(_ references) ([]*pkg, error) {
 
 // canonicalize gets the result of canonicalizing the packages using the results
 // of initializing the resolver from 'go list -m'.
-func (r *ModuleResolver) canonicalize(rootType gopathwalk.RootType, importPath, dir string, needsReplace bool) (res *pkg, err error) {
+func (r *ModuleResolver) canonicalize(info directoryPackageInfo) (*pkg, error) {
 	// Packages in GOROOT are already canonical, regardless of the std/cmd modules.
-	if rootType == gopathwalk.RootGOROOT {
+	if info.rootType == gopathwalk.RootGOROOT {
 		return &pkg{
-			importPathShort: importPath,
-			dir:             dir,
+			importPathShort: info.nonCanonicalImportPath,
+			dir:             info.dir,
+			packageName:     path.Base(info.nonCanonicalImportPath),
+			relevance:       0,
 		}, nil
 	}
 
+	importPath := info.nonCanonicalImportPath
+	relevance := 2
 	// Check if the directory is underneath a module that's in scope.
-	if mod := r.findModuleByDir(dir); mod != nil {
+	if mod := r.findModuleByDir(info.dir); mod != nil {
+		relevance = 1
 		// It is. If dir is the target of a replace directive,
 		// our guessed import path is wrong. Use the real one.
-		if mod.Dir == dir {
+		if mod.Dir == info.dir {
 			importPath = mod.Path
 		} else {
-			dirInMod := dir[len(mod.Dir)+len("/"):]
+			dirInMod := info.dir[len(mod.Dir)+len("/"):]
 			importPath = path.Join(mod.Path, filepath.ToSlash(dirInMod))
 		}
-	} else if needsReplace {
-		return nil, fmt.Errorf("needed this package to be in scope: %s", dir)
+	} else if info.needsReplace {
+		return nil, fmt.Errorf("package in %q is not valid without a replace statement", info.dir)
 	}
 
+	res := &pkg{
+		importPathShort: importPath,
+		dir:             info.dir,
+		packageName:     info.packageName, // may not be populated if the caller didn't ask for it
+		relevance:       relevance,
+	}
 	// We may have discovered a package that has a different version
 	// in scope already. Canonicalize to that one if possible.
 	if _, canonicalDir := r.findPackage(importPath); canonicalDir != "" {
-		dir = canonicalDir
+		res.dir = canonicalDir
 	}
-	return &pkg{
-		importPathShort: VendorlessPath(importPath),
-		dir:             dir,
-	}, nil
+	return res, nil
 }
 
-func (r *ModuleResolver) loadExports(ctx context.Context, expectPackage string, pkg *pkg) (map[string]bool, error) {
+func (r *ModuleResolver) loadExports(ctx context.Context, pkg *pkg) (string, []string, error) {
 	if err := r.init(); err != nil {
-		return nil, err
+		return "", nil, err
 	}
-	return loadExportsFromFiles(ctx, r.env, expectPackage, pkg.dir)
+	if info, ok := r.cacheLoad(pkg.dir); ok {
+		return r.cacheExports(ctx, r.env, info)
+	}
+	return loadExportsFromFiles(ctx, r.env, pkg.dir)
 }
 
-func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) (directoryPackageInfo, error) {
+func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) directoryPackageInfo {
 	subdir := ""
 	if dir != root.Path {
 		subdir = dir[len(root.Path)+len("/"):]
 	}
 	importPath := filepath.ToSlash(subdir)
 	if strings.HasPrefix(importPath, "vendor/") {
-		// Ignore vendor dirs. If -mod=vendor is on, then things
-		// should mostly just work, but when it's not vendor/
-		// is a mess. There's no easy way to tell if it's on.
-		// We can still find things in the mod cache and
-		// map them into /vendor when -mod=vendor is on.
-		return directoryPackageInfo{}, fmt.Errorf("vendor directory")
+		// Only enter vendor directories if they're explicitly requested as a root.
+		return directoryPackageInfo{
+			status: directoryScanned,
+			err:    fmt.Errorf("unwanted vendor directory"),
+		}
 	}
 	switch root.Type {
 	case gopathwalk.RootCurrentModule:
@@ -411,7 +495,7 @@ func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) (di
 			return directoryPackageInfo{
 				status: directoryScanned,
 				err:    fmt.Errorf("invalid module cache path: %v", subdir),
-			}, nil
+			}
 		}
 		modPath, err := module.DecodePath(filepath.ToSlash(matches[1]))
 		if err != nil {
@@ -421,35 +505,34 @@ func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) (di
 			return directoryPackageInfo{
 				status: directoryScanned,
 				err:    fmt.Errorf("decoding module cache path %q: %v", subdir, err),
-			}, nil
+			}
 		}
 		importPath = path.Join(modPath, filepath.ToSlash(matches[3]))
-	case gopathwalk.RootGOROOT:
-		importPath = subdir
 	}
 
+	modDir, modName := r.modInfo(dir)
 	result := directoryPackageInfo{
 		status:                 directoryScanned,
 		dir:                    dir,
+		rootType:               root.Type,
 		nonCanonicalImportPath: importPath,
 		needsReplace:           false,
+		moduleDir:              modDir,
+		moduleName:             modName,
 	}
 	if root.Type == gopathwalk.RootGOROOT {
 		// stdlib packages are always in scope, despite the confusing go.mod
-		return result, nil
+		return result
 	}
 	// Check that this package is not obviously impossible to import.
-	modFile := r.findModFile(dir)
-
-	modBytes, err := ioutil.ReadFile(modFile)
-	if err == nil && !strings.HasPrefix(importPath, modulePath(modBytes)) {
+	if !strings.HasPrefix(importPath, modName) {
 		// The module's declared path does not match
 		// its expected path. It probably needs a
 		// replace directive we don't have.
 		result.needsReplace = true
 	}
 
-	return result, nil
+	return result
 }
 
 // modCacheRegexp splits a path in a module cache into module, module version, and package.
@@ -498,3 +581,63 @@ func modulePath(mod []byte) string {
 	}
 	return "" // missing module path
 }
+
+var modFlagRegexp = regexp.MustCompile(`-mod[ =](\w+)`)
+
+// vendorEnabled indicates if vendoring is enabled.
+// Inspired by setDefaultBuildMod in modload/init.go
+func vendorEnabled(env *ProcessEnv) (*ModuleJSON, bool, error) {
+	mainMod, go114, err := getMainModuleAnd114(env)
+	if err != nil {
+		return nil, false, err
+	}
+	matches := modFlagRegexp.FindStringSubmatch(env.GOFLAGS)
+	var modFlag string
+	if len(matches) != 0 {
+		modFlag = matches[1]
+	}
+	if modFlag != "" {
+		// Don't override an explicit '-mod=' argument.
+		return mainMod, modFlag == "vendor", nil
+	}
+	if mainMod == nil || !go114 {
+		return mainMod, false, nil
+	}
+	// Check 1.14's automatic vendor mode.
+	if fi, err := os.Stat(filepath.Join(mainMod.Dir, "vendor")); err == nil && fi.IsDir() {
+		if mainMod.GoVersion != "" && semver.Compare("v"+mainMod.GoVersion, "v1.14") >= 0 {
+			// The Go version is at least 1.14, and a vendor directory exists.
+			// Set -mod=vendor by default.
+			return mainMod, true, nil
+		}
+	}
+	return mainMod, false, nil
+}
+
+// getMainModuleAnd114 gets the main module's information and whether the
+// go command in use is 1.14+. This is the information needed to figure out
+// if vendoring should be enabled.
+func getMainModuleAnd114(env *ProcessEnv) (*ModuleJSON, bool, error) {
+	const format = `{{.Path}}
+{{.Dir}}
+{{.GoMod}}
+{{.GoVersion}}
+{{range context.ReleaseTags}}{{if eq . "go1.14"}}{{.}}{{end}}{{end}}
+`
+	stdout, err := env.invokeGo("list", "-m", "-f", format)
+	if err != nil {
+		return nil, false, nil
+	}
+	lines := strings.Split(stdout.String(), "\n")
+	if len(lines) < 5 {
+		return nil, false, fmt.Errorf("unexpected stdout: %q", stdout)
+	}
+	mod := &ModuleJSON{
+		Path:      lines[0],
+		Dir:       lines[1],
+		GoMod:     lines[2],
+		GoVersion: lines[3],
+		Main:      true,
+	}
+	return mod, lines[4] == "go1.14", nil
+}

vendor/golang.org/x/tools/internal/imports/mod_cache.go

@@ -1,12 +1,13 @@
 package imports
 
 import (
+	"context"
+	"fmt"
 	"sync"
+
+	"golang.org/x/tools/internal/gopathwalk"
 )
 
-// ModuleResolver implements Resolver for modules using the go command as little
-// as feasible.
-//
 // To find packages to import, the resolver needs to know about all of the
 // the packages that could be imported. This includes packages that are
 // already in modules that are in (1) the current module, (2) replace targets,
@@ -30,6 +31,8 @@ type directoryPackageStatus int
 const (
 	_ directoryPackageStatus = iota
 	directoryScanned
+	nameLoaded
+	exportsLoaded
 )
 
 type directoryPackageInfo struct {
@@ -38,17 +41,30 @@ type directoryPackageInfo struct {
 	// err is non-nil when there was an error trying to reach status.
 	err error
 
-	// Set when status > directoryScanned.
+	// Set when status >= directoryScanned.
 
 	// dir is the absolute directory of this package.
-	dir string
-	// nonCanonicalImportPath is the expected import path for this package.
-	// This may not be an import path that can be used to import this package.
+	dir      string
+	rootType gopathwalk.RootType
+	// nonCanonicalImportPath is the package's expected import path. It may
+	// not actually be importable at that path.
 	nonCanonicalImportPath string
 	// needsReplace is true if the nonCanonicalImportPath does not match the
-	// the modules declared path, making it impossible to import without a
+	// module's declared path, making it impossible to import without a
 	// replace directive.
 	needsReplace bool
+
+	// Module-related information.
+	moduleDir  string // The directory that is the module root of this dir.
+	moduleName string // The module name that contains this dir.
+
+	// Set when status >= nameLoaded.
+
+	packageName string // the package name, as declared in the source.
+
+	// Set when status >= exportsLoaded.
+
+	exports []string
 }
 
 // reachedStatus returns true when info has a status at least target and any error associated with
@@ -63,8 +79,8 @@ func (info *directoryPackageInfo) reachedStatus(target directoryPackageStatus) (
 	return true, nil
 }
 
-// moduleCacheInfo is a concurrency safe map for storing information about
-// the directories in the module cache.
+// dirInfoCache is a concurrency safe map for storing information about
+// directories that may contain packages.
 //
 // The information in this cache is built incrementally. Entries are initialized in scan.
 // No new keys should be added in any other functions, as all directories containing
@@ -73,37 +89,30 @@ func (info *directoryPackageInfo) reachedStatus(target directoryPackageStatus) (
 // Other functions, including loadExports and findPackage, may update entries in this cache
 // as they discover new things about the directory.
 //
-// We do not need to protect the data in the cache for multiple writes, because it only stores
-// module cache directories, which do not change. If two competing stores take place, there will be
-// one store that wins. Although this could result in a loss of information it will not be incorrect
-// and may just result in recomputing the same result later.
+// The information in the cache is not expected to change for the cache's
+// lifetime, so there is no protection against competing writes. Users should
+// take care not to hold the cache across changes to the underlying files.
 //
 // TODO(suzmue): consider other concurrency strategies and data structures (RWLocks, sync.Map, etc)
-type moduleCacheInfo struct {
+type dirInfoCache struct {
 	mu sync.Mutex
-	// modCacheDirInfo stores information about packages in
-	// module cache directories. Keyed by absolute directory.
-	modCacheDirInfo map[string]*directoryPackageInfo
+	// dirs stores information about packages in directories, keyed by absolute path.
+	dirs map[string]*directoryPackageInfo
 }
 
 // Store stores the package info for dir.
-func (d *moduleCacheInfo) Store(dir string, info directoryPackageInfo) {
+func (d *dirInfoCache) Store(dir string, info directoryPackageInfo) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
-	d.modCacheDirInfo[dir] = &directoryPackageInfo{
-		status:                 info.status,
-		err:                    info.err,
-		dir:                    info.dir,
-		nonCanonicalImportPath: info.nonCanonicalImportPath,
-		needsReplace:           info.needsReplace,
-	}
+	stored := info // defensive copy
+	d.dirs[dir] = &stored
 }
 
 // Load returns a copy of the directoryPackageInfo for absolute directory dir.
-func (d *moduleCacheInfo) Load(dir string) (directoryPackageInfo, bool) {
+func (d *dirInfoCache) Load(dir string) (directoryPackageInfo, bool) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
-	info, ok := d.modCacheDirInfo[dir]
+	info, ok := d.dirs[dir]
 	if !ok {
 		return directoryPackageInfo{}, false
 	}
@@ -111,11 +120,46 @@ func (d *moduleCacheInfo) Load(dir string) (directoryPackageInfo, bool) {
 }
 
 // Keys returns the keys currently present in d.
-func (d *moduleCacheInfo) Keys() (keys []string) {
+func (d *dirInfoCache) Keys() (keys []string) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
-	for key := range d.modCacheDirInfo {
+	for key := range d.dirs {
 		keys = append(keys, key)
 	}
 	return keys
 }
+
+func (d *dirInfoCache) CachePackageName(info directoryPackageInfo) (directoryPackageInfo, error) {
+	if loaded, err := info.reachedStatus(nameLoaded); loaded {
+		return info, err
+	}
+	if scanned, err := info.reachedStatus(directoryScanned); !scanned || err != nil {
+		return info, fmt.Errorf("cannot read package name, scan error: %v", err)
+	}
+	info.packageName, info.err = packageDirToName(info.dir)
+	info.status = nameLoaded
+	d.Store(info.dir, info)
+	return info, info.err
+}
+
+func (d *dirInfoCache) CacheExports(ctx context.Context, env *ProcessEnv, info directoryPackageInfo) (string, []string, error) {
+	if reached, _ := info.reachedStatus(exportsLoaded); reached {
+		return info.packageName, info.exports, info.err
+	}
+	if reached, err := info.reachedStatus(nameLoaded); reached && err != nil {
+		return "", nil, err
+	}
+	info.packageName, info.exports, info.err = loadExportsFromFiles(ctx, env, info.dir)
+	if info.err == context.Canceled {
+		return info.packageName, info.exports, info.err
+	}
+	// The cache structure wants things to proceed linearly. We can skip a
+	// step here, but only if we succeed.
+	if info.status == nameLoaded || info.err == nil {
+		info.status = exportsLoaded
+	} else {
+		info.status = nameLoaded
+	}
+	d.Store(info.dir, info)
+	return info.packageName, info.exports, info.err
+}

vendor/golang.org/x/tools/internal/span/parse.go

@@ -0,0 +1,100 @@
+// Copyright 2019 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 span
+
+import (
+	"strconv"
+	"strings"
+	"unicode/utf8"
+)
+
+// Parse returns the location represented by the input.
+// All inputs are valid locations, as they can always be a pure filename.
+// The returned span will be normalized, and thus if printed may produce a
+// different string.
+func Parse(input string) Span {
+	// :0:0#0-0:0#0
+	valid := input
+	var hold, offset int
+	hadCol := false
+	suf := rstripSuffix(input)
+	if suf.sep == "#" {
+		offset = suf.num
+		suf = rstripSuffix(suf.remains)
+	}
+	if suf.sep == ":" {
+		valid = suf.remains
+		hold = suf.num
+		hadCol = true
+		suf = rstripSuffix(suf.remains)
+	}
+	switch {
+	case suf.sep == ":":
+		return New(NewURI(suf.remains), NewPoint(suf.num, hold, offset), Point{})
+	case suf.sep == "-":
+		// we have a span, fall out of the case to continue
+	default:
+		// separator not valid, rewind to either the : or the start
+		return New(NewURI(valid), NewPoint(hold, 0, offset), Point{})
+	}
+	// only the span form can get here
+	// at this point we still don't know what the numbers we have mean
+	// if have not yet seen a : then we might have either a line or a column depending
+	// on whether start has a column or not
+	// we build an end point and will fix it later if needed
+	end := NewPoint(suf.num, hold, offset)
+	hold, offset = 0, 0
+	suf = rstripSuffix(suf.remains)
+	if suf.sep == "#" {
+		offset = suf.num
+		suf = rstripSuffix(suf.remains)
+	}
+	if suf.sep != ":" {
+		// turns out we don't have a span after all, rewind
+		return New(NewURI(valid), end, Point{})
+	}
+	valid = suf.remains
+	hold = suf.num
+	suf = rstripSuffix(suf.remains)
+	if suf.sep != ":" {
+		// line#offset only
+		return New(NewURI(valid), NewPoint(hold, 0, offset), end)
+	}
+	// we have a column, so if end only had one number, it is also the column
+	if !hadCol {
+		end = NewPoint(suf.num, end.v.Line, end.v.Offset)
+	}
+	return New(NewURI(suf.remains), NewPoint(suf.num, hold, offset), end)
+}
+
+type suffix struct {
+	remains string
+	sep     string
+	num     int
+}
+
+func rstripSuffix(input string) suffix {
+	if len(input) == 0 {
+		return suffix{"", "", -1}
+	}
+	remains := input
+	num := -1
+	// first see if we have a number at the end
+	last := strings.LastIndexFunc(remains, func(r rune) bool { return r < '0' || r > '9' })
+	if last >= 0 && last < len(remains)-1 {
+		number, err := strconv.ParseInt(remains[last+1:], 10, 64)
+		if err == nil {
+			num = int(number)
+			remains = remains[:last+1]
+		}
+	}
+	// now see if we have a trailing separator
+	r, w := utf8.DecodeLastRuneInString(remains)
+	if r != ':' && r != '#' && r == '#' {
+		return suffix{input, "", -1}
+	}
+	remains = remains[:len(remains)-w]
+	return suffix{remains, string(r), num}
+}

vendor/golang.org/x/tools/internal/span/span.go

@@ -0,0 +1,285 @@
+// Copyright 2019 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 span contains support for representing with positions and ranges in
+// text files.
+package span
+
+import (
+	"encoding/json"
+	"fmt"
+	"path"
+)
+
+// Span represents a source code range in standardized form.
+type Span struct {
+	v span
+}
+
+// Point represents a single point within a file.
+// In general this should only be used as part of a Span, as on its own it
+// does not carry enough information.
+type Point struct {
+	v point
+}
+
+type span struct {
+	URI   URI   `json:"uri"`
+	Start point `json:"start"`
+	End   point `json:"end"`
+}
+
+type point struct {
+	Line   int `json:"line"`
+	Column int `json:"column"`
+	Offset int `json:"offset"`
+}
+
+// Invalid is a span that reports false from IsValid
+var Invalid = Span{v: span{Start: invalidPoint.v, End: invalidPoint.v}}
+
+var invalidPoint = Point{v: point{Line: 0, Column: 0, Offset: -1}}
+
+// Converter is the interface to an object that can convert between line:column
+// and offset forms for a single file.
+type Converter interface {
+	//ToPosition converts from an offset to a line:column pair.
+	ToPosition(offset int) (int, int, error)
+	//ToOffset converts from a line:column pair to an offset.
+	ToOffset(line, col int) (int, error)
+}
+
+func New(uri URI, start Point, end Point) Span {
+	s := Span{v: span{URI: uri, Start: start.v, End: end.v}}
+	s.v.clean()
+	return s
+}
+
+func NewPoint(line, col, offset int) Point {
+	p := Point{v: point{Line: line, Column: col, Offset: offset}}
+	p.v.clean()
+	return p
+}
+
+func Compare(a, b Span) int {
+	if r := CompareURI(a.URI(), b.URI()); r != 0 {
+		return r
+	}
+	if r := comparePoint(a.v.Start, b.v.Start); r != 0 {
+		return r
+	}
+	return comparePoint(a.v.End, b.v.End)
+}
+
+func ComparePoint(a, b Point) int {
+	return comparePoint(a.v, b.v)
+}
+
+func comparePoint(a, b point) int {
+	if !a.hasPosition() {
+		if a.Offset < b.Offset {
+			return -1
+		}
+		if a.Offset > b.Offset {
+			return 1
+		}
+		return 0
+	}
+	if a.Line < b.Line {
+		return -1
+	}
+	if a.Line > b.Line {
+		return 1
+	}
+	if a.Column < b.Column {
+		return -1
+	}
+	if a.Column > b.Column {
+		return 1
+	}
+	return 0
+}
+
+func (s Span) HasPosition() bool             { return s.v.Start.hasPosition() }
+func (s Span) HasOffset() bool               { return s.v.Start.hasOffset() }
+func (s Span) IsValid() bool                 { return s.v.Start.isValid() }
+func (s Span) IsPoint() bool                 { return s.v.Start == s.v.End }
+func (s Span) URI() URI                      { return s.v.URI }
+func (s Span) Start() Point                  { return Point{s.v.Start} }
+func (s Span) End() Point                    { return Point{s.v.End} }
+func (s *Span) MarshalJSON() ([]byte, error) { return json.Marshal(&s.v) }
+func (s *Span) UnmarshalJSON(b []byte) error { return json.Unmarshal(b, &s.v) }
+
+func (p Point) HasPosition() bool             { return p.v.hasPosition() }
+func (p Point) HasOffset() bool               { return p.v.hasOffset() }
+func (p Point) IsValid() bool                 { return p.v.isValid() }
+func (p *Point) MarshalJSON() ([]byte, error) { return json.Marshal(&p.v) }
+func (p *Point) UnmarshalJSON(b []byte) error { return json.Unmarshal(b, &p.v) }
+func (p Point) Line() int {
+	if !p.v.hasPosition() {
+		panic(fmt.Errorf("position not set in %v", p.v))
+	}
+	return p.v.Line
+}
+func (p Point) Column() int {
+	if !p.v.hasPosition() {
+		panic(fmt.Errorf("position not set in %v", p.v))
+	}
+	return p.v.Column
+}
+func (p Point) Offset() int {
+	if !p.v.hasOffset() {
+		panic(fmt.Errorf("offset not set in %v", p.v))
+	}
+	return p.v.Offset
+}
+
+func (p point) hasPosition() bool { return p.Line > 0 }
+func (p point) hasOffset() bool   { return p.Offset >= 0 }
+func (p point) isValid() bool     { return p.hasPosition() || p.hasOffset() }
+func (p point) isZero() bool {
+	return (p.Line == 1 && p.Column == 1) || (!p.hasPosition() && p.Offset == 0)
+}
+
+func (s *span) clean() {
+	//this presumes the points are already clean
+	if !s.End.isValid() || (s.End == point{}) {
+		s.End = s.Start
+	}
+}
+
+func (p *point) clean() {
+	if p.Line < 0 {
+		p.Line = 0
+	}
+	if p.Column <= 0 {
+		if p.Line > 0 {
+			p.Column = 1
+		} else {
+			p.Column = 0
+		}
+	}
+	if p.Offset == 0 && (p.Line > 1 || p.Column > 1) {
+		p.Offset = -1
+	}
+}
+
+// Format implements fmt.Formatter to print the Location in a standard form.
+// The format produced is one that can be read back in using Parse.
+func (s Span) Format(f fmt.State, c rune) {
+	fullForm := f.Flag('+')
+	preferOffset := f.Flag('#')
+	// we should always have a uri, simplify if it is file format
+	//TODO: make sure the end of the uri is unambiguous
+	uri := string(s.v.URI)
+	if c == 'f' {
+		uri = path.Base(uri)
+	} else if !fullForm {
+		uri = s.v.URI.Filename()
+	}
+	fmt.Fprint(f, uri)
+	if !s.IsValid() || (!fullForm && s.v.Start.isZero() && s.v.End.isZero()) {
+		return
+	}
+	// see which bits of start to write
+	printOffset := s.HasOffset() && (fullForm || preferOffset || !s.HasPosition())
+	printLine := s.HasPosition() && (fullForm || !printOffset)
+	printColumn := printLine && (fullForm || (s.v.Start.Column > 1 || s.v.End.Column > 1))
+	fmt.Fprint(f, ":")
+	if printLine {
+		fmt.Fprintf(f, "%d", s.v.Start.Line)
+	}
+	if printColumn {
+		fmt.Fprintf(f, ":%d", s.v.Start.Column)
+	}
+	if printOffset {
+		fmt.Fprintf(f, "#%d", s.v.Start.Offset)
+	}
+	// start is written, do we need end?
+	if s.IsPoint() {
+		return
+	}
+	// we don't print the line if it did not change
+	printLine = fullForm || (printLine && s.v.End.Line > s.v.Start.Line)
+	fmt.Fprint(f, "-")
+	if printLine {
+		fmt.Fprintf(f, "%d", s.v.End.Line)
+	}
+	if printColumn {
+		if printLine {
+			fmt.Fprint(f, ":")
+		}
+		fmt.Fprintf(f, "%d", s.v.End.Column)
+	}
+	if printOffset {
+		fmt.Fprintf(f, "#%d", s.v.End.Offset)
+	}
+}
+
+func (s Span) WithPosition(c Converter) (Span, error) {
+	if err := s.update(c, true, false); err != nil {
+		return Span{}, err
+	}
+	return s, nil
+}
+
+func (s Span) WithOffset(c Converter) (Span, error) {
+	if err := s.update(c, false, true); err != nil {
+		return Span{}, err
+	}
+	return s, nil
+}
+
+func (s Span) WithAll(c Converter) (Span, error) {
+	if err := s.update(c, true, true); err != nil {
+		return Span{}, err
+	}
+	return s, nil
+}
+
+func (s *Span) update(c Converter, withPos, withOffset bool) error {
+	if !s.IsValid() {
+		return fmt.Errorf("cannot add information to an invalid span")
+	}
+	if withPos && !s.HasPosition() {
+		if err := s.v.Start.updatePosition(c); err != nil {
+			return err
+		}
+		if s.v.End.Offset == s.v.Start.Offset {
+			s.v.End = s.v.Start
+		} else if err := s.v.End.updatePosition(c); err != nil {
+			return err
+		}
+	}
+	if withOffset && (!s.HasOffset() || (s.v.End.hasPosition() && !s.v.End.hasOffset())) {
+		if err := s.v.Start.updateOffset(c); err != nil {
+			return err
+		}
+		if s.v.End.Line == s.v.Start.Line && s.v.End.Column == s.v.Start.Column {
+			s.v.End.Offset = s.v.Start.Offset
+		} else if err := s.v.End.updateOffset(c); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (p *point) updatePosition(c Converter) error {
+	line, col, err := c.ToPosition(p.Offset)
+	if err != nil {
+		return err
+	}
+	p.Line = line
+	p.Column = col
+	return nil
+}
+
+func (p *point) updateOffset(c Converter) error {
+	offset, err := c.ToOffset(p.Line, p.Column)
+	if err != nil {
+		return err
+	}
+	p.Offset = offset
+	return nil
+}

vendor/golang.org/x/tools/internal/span/token.go

@@ -0,0 +1,151 @@
+// Copyright 2019 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 span
+
+import (
+	"fmt"
+	"go/token"
+)
+
+// Range represents a source code range in token.Pos form.
+// It also carries the FileSet that produced the positions, so that it is
+// self contained.
+type Range struct {
+	FileSet *token.FileSet
+	Start   token.Pos
+	End     token.Pos
+}
+
+// TokenConverter is a Converter backed by a token file set and file.
+// It uses the file set methods to work out the conversions, which
+// makes it fast and does not require the file contents.
+type TokenConverter struct {
+	fset *token.FileSet
+	file *token.File
+}
+
+// NewRange creates a new Range from a FileSet and two positions.
+// To represent a point pass a 0 as the end pos.
+func NewRange(fset *token.FileSet, start, end token.Pos) Range {
+	return Range{
+		FileSet: fset,
+		Start:   start,
+		End:     end,
+	}
+}
+
+// NewTokenConverter returns an implementation of Converter backed by a
+// token.File.
+func NewTokenConverter(fset *token.FileSet, f *token.File) *TokenConverter {
+	return &TokenConverter{fset: fset, file: f}
+}
+
+// NewContentConverter returns an implementation of Converter for the
+// given file content.
+func NewContentConverter(filename string, content []byte) *TokenConverter {
+	fset := token.NewFileSet()
+	f := fset.AddFile(filename, -1, len(content))
+	f.SetLinesForContent(content)
+	return &TokenConverter{fset: fset, file: f}
+}
+
+// IsPoint returns true if the range represents a single point.
+func (r Range) IsPoint() bool {
+	return r.Start == r.End
+}
+
+// Span converts a Range to a Span that represents the Range.
+// It will fill in all the members of the Span, calculating the line and column
+// information.
+func (r Range) Span() (Span, error) {
+	f := r.FileSet.File(r.Start)
+	if f == nil {
+		return Span{}, fmt.Errorf("file not found in FileSet")
+	}
+	s := Span{v: span{URI: FileURI(f.Name())}}
+	var err error
+	s.v.Start.Offset, err = offset(f, r.Start)
+	if err != nil {
+		return Span{}, err
+	}
+	if r.End.IsValid() {
+		s.v.End.Offset, err = offset(f, r.End)
+		if err != nil {
+			return Span{}, err
+		}
+	}
+	s.v.Start.clean()
+	s.v.End.clean()
+	s.v.clean()
+	converter := NewTokenConverter(r.FileSet, f)
+	return s.WithPosition(converter)
+}
+
+// offset is a copy of the Offset function in go/token, but with the adjustment
+// that it does not panic on invalid positions.
+func offset(f *token.File, pos token.Pos) (int, error) {
+	if int(pos) < f.Base() || int(pos) > f.Base()+f.Size() {
+		return 0, fmt.Errorf("invalid pos")
+	}
+	return int(pos) - f.Base(), nil
+}
+
+// Range converts a Span to a Range that represents the Span for the supplied
+// File.
+func (s Span) Range(converter *TokenConverter) (Range, error) {
+	s, err := s.WithOffset(converter)
+	if err != nil {
+		return Range{}, err
+	}
+	// go/token will panic if the offset is larger than the file's size,
+	// so check here to avoid panicking.
+	if s.Start().Offset() > converter.file.Size() {
+		return Range{}, fmt.Errorf("start offset %v is past the end of the file %v", s.Start(), converter.file.Size())
+	}
+	if s.End().Offset() > converter.file.Size() {
+		return Range{}, fmt.Errorf("end offset %v is past the end of the file %v", s.End(), converter.file.Size())
+	}
+	return Range{
+		FileSet: converter.fset,
+		Start:   converter.file.Pos(s.Start().Offset()),
+		End:     converter.file.Pos(s.End().Offset()),
+	}, nil
+}
+
+func (l *TokenConverter) ToPosition(offset int) (int, int, error) {
+	if offset > l.file.Size() {
+		return 0, 0, fmt.Errorf("offset %v is past the end of the file %v", offset, l.file.Size())
+	}
+	pos := l.file.Pos(offset)
+	p := l.fset.Position(pos)
+	if offset == l.file.Size() {
+		return p.Line + 1, 1, nil
+	}
+	return p.Line, p.Column, nil
+}
+
+func (l *TokenConverter) ToOffset(line, col int) (int, error) {
+	if line < 0 {
+		return -1, fmt.Errorf("line is not valid")
+	}
+	lineMax := l.file.LineCount() + 1
+	if line > lineMax {
+		return -1, fmt.Errorf("line is beyond end of file %v", lineMax)
+	} else if line == lineMax {
+		if col > 1 {
+			return -1, fmt.Errorf("column is beyond end of file")
+		}
+		// at the end of the file, allowing for a trailing eol
+		return l.file.Size(), nil
+	}
+	pos := lineStart(l.file, line)
+	if !pos.IsValid() {
+		return -1, fmt.Errorf("line is not in file")
+	}
+	// we assume that column is in bytes here, and that the first byte of a
+	// line is at column 1
+	pos += token.Pos(col - 1)
+	return offset(l.file, pos)
+}

vendor/golang.org/x/tools/internal/span/token111.go

@@ -0,0 +1,39 @@
+// Copyright 2019 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.
+
+// +build !go1.12
+
+package span
+
+import (
+	"go/token"
+)
+
+// lineStart is the pre-Go 1.12 version of (*token.File).LineStart. For Go
+// versions <= 1.11, we borrow logic from the analysisutil package.
+// TODO(rstambler): Delete this file when we no longer support Go 1.11.
+func lineStart(f *token.File, line int) token.Pos {
+	// Use binary search to find the start offset of this line.
+
+	min := 0        // inclusive
+	max := f.Size() // exclusive
+	for {
+		offset := (min + max) / 2
+		pos := f.Pos(offset)
+		posn := f.Position(pos)
+		if posn.Line == line {
+			return pos - (token.Pos(posn.Column) - 1)
+		}
+
+		if min+1 >= max {
+			return token.NoPos
+		}
+
+		if posn.Line < line {
+			min = offset
+		} else {
+			max = offset
+		}
+	}
+}

vendor/golang.org/x/tools/internal/span/token112.go

@@ -0,0 +1,16 @@
+// Copyright 2019 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.
+
+// +build go1.12
+
+package span
+
+import (
+	"go/token"
+)
+
+// TODO(rstambler): Delete this file when we no longer support Go 1.11.
+func lineStart(f *token.File, line int) token.Pos {
+	return f.LineStart(line)
+}

vendor/golang.org/x/tools/internal/span/uri.go

@@ -0,0 +1,152 @@
+// Copyright 2019 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 span
+
+import (
+	"fmt"
+	"net/url"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"unicode"
+)
+
+const fileScheme = "file"
+
+// URI represents the full URI for a file.
+type URI string
+
+// Filename returns the file path for the given URI.
+// It is an error to call this on a URI that is not a valid filename.
+func (uri URI) Filename() string {
+	filename, err := filename(uri)
+	if err != nil {
+		panic(err)
+	}
+	return filepath.FromSlash(filename)
+}
+
+func filename(uri URI) (string, error) {
+	if uri == "" {
+		return "", nil
+	}
+	u, err := url.ParseRequestURI(string(uri))
+	if err != nil {
+		return "", err
+	}
+	if u.Scheme != fileScheme {
+		return "", fmt.Errorf("only file URIs are supported, got %q from %q", u.Scheme, uri)
+	}
+	if isWindowsDriveURI(u.Path) {
+		u.Path = u.Path[1:]
+	}
+	return u.Path, nil
+}
+
+// NewURI returns a span URI for the string.
+// It will attempt to detect if the string is a file path or uri.
+func NewURI(s string) URI {
+	if u, err := url.PathUnescape(s); err == nil {
+		s = u
+	}
+	if strings.HasPrefix(s, fileScheme+"://") {
+		return URI(s)
+	}
+	return FileURI(s)
+}
+
+func CompareURI(a, b URI) int {
+	if equalURI(a, b) {
+		return 0
+	}
+	if a < b {
+		return -1
+	}
+	return 1
+}
+
+func equalURI(a, b URI) bool {
+	if a == b {
+		return true
+	}
+	// If we have the same URI basename, we may still have the same file URIs.
+	if !strings.EqualFold(path.Base(string(a)), path.Base(string(b))) {
+		return false
+	}
+	fa, err := filename(a)
+	if err != nil {
+		return false
+	}
+	fb, err := filename(b)
+	if err != nil {
+		return false
+	}
+	// Stat the files to check if they are equal.
+	infoa, err := os.Stat(filepath.FromSlash(fa))
+	if err != nil {
+		return false
+	}
+	infob, err := os.Stat(filepath.FromSlash(fb))
+	if err != nil {
+		return false
+	}
+	return os.SameFile(infoa, infob)
+}
+
+// FileURI returns a span URI for the supplied file path.
+// It will always have the file scheme.
+func FileURI(path string) URI {
+	if path == "" {
+		return ""
+	}
+	// Handle standard library paths that contain the literal "$GOROOT".
+	// TODO(rstambler): The go/packages API should allow one to determine a user's $GOROOT.
+	const prefix = "$GOROOT"
+	if len(path) >= len(prefix) && strings.EqualFold(prefix, path[:len(prefix)]) {
+		suffix := path[len(prefix):]
+		path = runtime.GOROOT() + suffix
+	}
+	if !isWindowsDrivePath(path) {
+		if abs, err := filepath.Abs(path); err == nil {
+			path = abs
+		}
+	}
+	// Check the file path again, in case it became absolute.
+	if isWindowsDrivePath(path) {
+		path = "/" + path
+	}
+	path = filepath.ToSlash(path)
+	u := url.URL{
+		Scheme: fileScheme,
+		Path:   path,
+	}
+	uri := u.String()
+	if unescaped, err := url.PathUnescape(uri); err == nil {
+		uri = unescaped
+	}
+	return URI(uri)
+}
+
+// isWindowsDrivePath returns true if the file path is of the form used by
+// Windows. We check if the path begins with a drive letter, followed by a ":".
+func isWindowsDrivePath(path string) bool {
+	if len(path) < 4 {
+		return false
+	}
+	return unicode.IsLetter(rune(path[0])) && path[1] == ':'
+}
+
+// isWindowsDriveURI returns true if the file URI is of the format used by
+// Windows URIs. The url.Parse package does not specially handle Windows paths
+// (see https://golang.org/issue/6027). We check if the URI path has
+// a drive prefix (e.g. "/C:"). If so, we trim the leading "/".
+func isWindowsDriveURI(uri string) bool {
+	if len(uri) < 4 {
+		return false
+	}
+	return uri[0] == '/' && unicode.IsLetter(rune(uri[1])) && uri[2] == ':'
+}

vendor/golang.org/x/tools/internal/span/utf16.go

@@ -0,0 +1,94 @@
+// Copyright 2019 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 span
+
+import (
+	"fmt"
+	"unicode/utf16"
+	"unicode/utf8"
+)
+
+// ToUTF16Column calculates the utf16 column expressed by the point given the
+// supplied file contents.
+// This is used to convert from the native (always in bytes) column
+// representation and the utf16 counts used by some editors.
+func ToUTF16Column(p Point, content []byte) (int, error) {
+	if content == nil {
+		return -1, fmt.Errorf("ToUTF16Column: missing content")
+	}
+	if !p.HasPosition() {
+		return -1, fmt.Errorf("ToUTF16Column: point is missing position")
+	}
+	if !p.HasOffset() {
+		return -1, fmt.Errorf("ToUTF16Column: point is missing offset")
+	}
+	offset := p.Offset()      // 0-based
+	colZero := p.Column() - 1 // 0-based
+	if colZero == 0 {
+		// 0-based column 0, so it must be chr 1
+		return 1, nil
+	} else if colZero < 0 {
+		return -1, fmt.Errorf("ToUTF16Column: column is invalid (%v)", colZero)
+	}
+	// work out the offset at the start of the line using the column
+	lineOffset := offset - colZero
+	if lineOffset < 0 || offset > len(content) {
+		return -1, fmt.Errorf("ToUTF16Column: offsets %v-%v outside file contents (%v)", lineOffset, offset, len(content))
+	}
+	// Use the offset to pick out the line start.
+	// This cannot panic: offset > len(content) and lineOffset < offset.
+	start := content[lineOffset:]
+
+	// Now, truncate down to the supplied column.
+	start = start[:colZero]
+
+	// and count the number of utf16 characters
+	// in theory we could do this by hand more efficiently...
+	return len(utf16.Encode([]rune(string(start)))) + 1, nil
+}
+
+// FromUTF16Column advances the point by the utf16 character offset given the
+// supplied line contents.
+// This is used to convert from the utf16 counts used by some editors to the
+// native (always in bytes) column representation.
+func FromUTF16Column(p Point, chr int, content []byte) (Point, error) {
+	if !p.HasOffset() {
+		return Point{}, fmt.Errorf("FromUTF16Column: point is missing offset")
+	}
+	// if chr is 1 then no adjustment needed
+	if chr <= 1 {
+		return p, nil
+	}
+	if p.Offset() >= len(content) {
+		return p, fmt.Errorf("FromUTF16Column: offset (%v) greater than length of content (%v)", p.Offset(), len(content))
+	}
+	remains := content[p.Offset():]
+	// scan forward the specified number of characters
+	for count := 1; count < chr; count++ {
+		if len(remains) <= 0 {
+			return Point{}, fmt.Errorf("FromUTF16Column: chr goes beyond the content")
+		}
+		r, w := utf8.DecodeRune(remains)
+		if r == '\n' {
+			// Per the LSP spec:
+			//
+			// > If the character value is greater than the line length it
+			// > defaults back to the line length.
+			break
+		}
+		remains = remains[w:]
+		if r >= 0x10000 {
+			// a two point rune
+			count++
+			// if we finished in a two point rune, do not advance past the first
+			if count >= chr {
+				break
+			}
+		}
+		p.v.Column += w
+		p.v.Offset += w
+	}
+	return p, nil
+}