update dependencies (#6267)

Signed-off-by: hongming <coder.scala@gmail.com>
(cherry picked from commit cfebd96a1f)

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:generate go run mkstdlib.go
-
 // Package imports implements a Go pretty-printer (like package "go/format")
 // that also adds or removes import statements as necessary.
 package imports
@@ -11,6 +9,7 @@ package imports
 import (
 	"bufio"
 	"bytes"
+	"context"
 	"fmt"
 	"go/ast"
 	"go/format"
@@ -23,6 +22,7 @@ import (
 	"strings"
 
 	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/internal/event"
 )
 
 // Options is golang.org/x/tools/imports.Options with extra internal-only options.
@@ -66,14 +66,17 @@ func Process(filename string, src []byte, opt *Options) (formatted []byte, err e
 //
 // Note that filename's directory influences which imports can be chosen,
 // so it is important that filename be accurate.
-func FixImports(filename string, src []byte, opt *Options) (fixes []*ImportFix, err error) {
+func FixImports(ctx context.Context, filename string, src []byte, opt *Options) (fixes []*ImportFix, err error) {
+	ctx, done := event.Start(ctx, "imports.FixImports")
+	defer done()
+
 	fileSet := token.NewFileSet()
 	file, _, err := parse(fileSet, filename, src, opt)
 	if err != nil {
 		return nil, err
 	}
 
-	return getFixes(fileSet, file, filename, opt.Env)
+	return getFixes(ctx, fileSet, file, filename, opt.Env)
 }
 
 // ApplyFixes applies all of the fixes to the file and formats it. extraMode
@@ -83,7 +86,7 @@ func ApplyFixes(fixes []*ImportFix, filename string, src []byte, opt *Options, e
 	// Don't use parse() -- we don't care about fragments or statement lists
 	// here, and we need to work with unparseable files.
 	fileSet := token.NewFileSet()
-	parserMode := parser.Mode(0)
+	parserMode := parser.SkipObjectResolution
 	if opt.Comments {
 		parserMode |= parser.ParseComments
 	}
@@ -104,7 +107,7 @@ func ApplyFixes(fixes []*ImportFix, filename string, src []byte, opt *Options, e
 }
 
 // formatFile formats the file syntax tree.
-// It may mutate the token.FileSet.
+// It may mutate the token.FileSet and the ast.File.
 //
 // If an adjust function is provided, it is called after formatting
 // with the original source (formatFile's src parameter) and the
@@ -162,7 +165,7 @@ func formatFile(fset *token.FileSet, file *ast.File, src []byte, adjust func(ori
 // parse parses src, which was read from filename,
 // as a Go source file or statement list.
 func parse(fset *token.FileSet, filename string, src []byte, opt *Options) (*ast.File, func(orig, src []byte) []byte, error) {
-	parserMode := parser.Mode(0)
+	var parserMode parser.Mode // legacy ast.Object resolution is required here
 	if opt.Comments {
 		parserMode |= parser.ParseComments
 	}
@@ -231,7 +234,7 @@ func parse(fset *token.FileSet, filename string, src []byte, opt *Options) (*ast
 			src = src[:len(src)-len("}\n")]
 			// Gofmt has also indented the function body one level.
 			// Remove that indent.
-			src = bytes.Replace(src, []byte("\n\t"), []byte("\n"), -1)
+			src = bytes.ReplaceAll(src, []byte("\n\t"), []byte("\n"))
 			return matchSpace(orig, src)
 		}
 		return file, adjust, nil

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

@@ -9,7 +9,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path"
 	"path/filepath"
@@ -19,80 +18,141 @@ import (
 	"strings"
 
 	"golang.org/x/mod/module"
+	"golang.org/x/tools/internal/event"
 	"golang.org/x/tools/internal/gocommand"
 	"golang.org/x/tools/internal/gopathwalk"
+	"golang.org/x/tools/internal/stdlib"
 )
 
-// ModuleResolver implements resolver for modules using the go command as little
-// as feasible.
+// Notes(rfindley): ModuleResolver appears to be heavily optimized for scanning
+// as fast as possible, which is desirable for a call to goimports from the
+// command line, but it doesn't work as well for gopls, where it suffers from
+// slow startup (golang/go#44863) and intermittent hanging (golang/go#59216),
+// both caused by populating the cache, albeit in slightly different ways.
+//
+// A high level list of TODOs:
+//  - Optimize the scan itself, as there is some redundancy statting and
+//    reading go.mod files.
+//  - Invert the relationship between ProcessEnv and Resolver (see the
+//    docstring of ProcessEnv).
+//  - Make it easier to use an external resolver implementation.
+//
+// Smaller TODOs are annotated in the code below.
+
+// ModuleResolver implements the Resolver interface for a workspace using
+// modules.
+//
+// A goal of the ModuleResolver is to invoke the Go command as little as
+// possible. To this end, it runs the Go command only for listing module
+// information (i.e. `go list -m -e -json ...`). Package scanning, the process
+// of loading package information for the modules, is implemented internally
+// via the scan method.
+//
+// It has two types of state: the state derived from the go command, which
+// is populated by init, and the state derived from scans, which is populated
+// via scan. A root is considered scanned if it has been walked to discover
+// directories. However, if the scan did not require additional information
+// from the directory (such as package name or exports), the directory
+// information itself may be partially populated. It will be lazily filled in
+// as needed by scans, using the scanCallback.
 type ModuleResolver struct {
-	env            *ProcessEnv
-	moduleCacheDir string
-	dummyVendorMod *gocommand.ModuleJSON // If vendoring is enabled, the pseudo-module that represents the /vendor directory.
-	roots          []gopathwalk.Root
-	scanSema       chan struct{} // scanSema prevents concurrent scans and guards scannedRoots.
-	scannedRoots   map[gopathwalk.Root]bool
+	env *ProcessEnv
 
-	initialized   bool
-	mains         []*gocommand.ModuleJSON
-	mainByDir     map[string]*gocommand.ModuleJSON
-	modsByModPath []*gocommand.ModuleJSON // All modules, ordered by # of path components in module Path...
-	modsByDir     []*gocommand.ModuleJSON // ...or Dir.
+	// Module state, populated during construction
+	dummyVendorMod *gocommand.ModuleJSON            // if vendoring is enabled, a pseudo-module to represent the /vendor directory
+	moduleCacheDir string                           // GOMODCACHE, inferred from GOPATH if unset
+	roots          []gopathwalk.Root                // roots to scan, in approximate order of importance
+	mains          []*gocommand.ModuleJSON          // main modules
+	mainByDir      map[string]*gocommand.ModuleJSON // module information by dir, to join with roots
+	modsByModPath  []*gocommand.ModuleJSON          // all modules, ordered by # of path components in their module path
+	modsByDir      []*gocommand.ModuleJSON          // ...or by the number of path components in their Dir.
 
-	// moduleCacheCache stores information about the module cache.
-	moduleCacheCache *dirInfoCache
-	otherCache       *dirInfoCache
+	// Scanning state, populated by scan
+
+	// scanSema prevents concurrent scans, and guards scannedRoots and the cache
+	// fields below (though the caches themselves are concurrency safe).
+	// Receive to acquire, send to release.
+	scanSema     chan struct{}
+	scannedRoots map[gopathwalk.Root]bool // if true, root has been walked
+
+	// Caches of directory info, populated by scans and scan callbacks
+	//
+	// moduleCacheCache stores cached information about roots in the module
+	// cache, which are immutable and therefore do not need to be invalidated.
+	//
+	// otherCache stores information about all other roots (even GOROOT), which
+	// may change.
+	moduleCacheCache *DirInfoCache
+	otherCache       *DirInfoCache
 }
 
-func newModuleResolver(e *ProcessEnv) *ModuleResolver {
+// newModuleResolver returns a new module-aware goimports resolver.
+//
+// Note: use caution when modifying this constructor: changes must also be
+// reflected in ModuleResolver.ClearForNewScan.
+func newModuleResolver(e *ProcessEnv, moduleCacheCache *DirInfoCache) (*ModuleResolver, error) {
 	r := &ModuleResolver{
 		env:      e,
 		scanSema: make(chan struct{}, 1),
 	}
-	r.scanSema <- struct{}{}
-	return r
-}
-
-func (r *ModuleResolver) init() error {
-	if r.initialized {
-		return nil
-	}
+	r.scanSema <- struct{}{} // release
 
 	goenv, err := r.env.goEnv()
 	if err != nil {
-		return err
+		return nil, err
 	}
+
+	// TODO(rfindley): can we refactor to share logic with r.env.invokeGo?
 	inv := gocommand.Invocation{
 		BuildFlags: r.env.BuildFlags,
 		ModFlag:    r.env.ModFlag,
-		ModFile:    r.env.ModFile,
 		Env:        r.env.env(),
 		Logf:       r.env.Logf,
 		WorkingDir: r.env.WorkingDir,
 	}
 
 	vendorEnabled := false
-	var mainModVendor *gocommand.ModuleJSON
+	var mainModVendor *gocommand.ModuleJSON    // for module vendoring
+	var mainModsVendor []*gocommand.ModuleJSON // for workspace vendoring
 
-	// Module vendor directories are ignored in workspace mode:
-	// https://go.googlesource.com/proposal/+/master/design/45713-workspace.md
-	if len(r.env.Env["GOWORK"]) == 0 {
+	goWork := r.env.Env["GOWORK"]
+	if len(goWork) == 0 {
+		// TODO(rfindley): VendorEnabled runs the go command to get GOFLAGS, but
+		// they should be available from the ProcessEnv. Can we avoid the redundant
+		// invocation?
 		vendorEnabled, mainModVendor, err = gocommand.VendorEnabled(context.TODO(), inv, r.env.GocmdRunner)
 		if err != nil {
-			return err
+			return nil, err
+		}
+	} else {
+		vendorEnabled, mainModsVendor, err = gocommand.WorkspaceVendorEnabled(context.Background(), inv, r.env.GocmdRunner)
+		if err != nil {
+			return nil, err
 		}
 	}
 
-	if mainModVendor != nil && vendorEnabled {
-		// Vendor mode is on, so all the non-Main modules are irrelevant,
-		// and we need to search /vendor for everything.
-		r.mains = []*gocommand.ModuleJSON{mainModVendor}
-		r.dummyVendorMod = &gocommand.ModuleJSON{
-			Path: "",
-			Dir:  filepath.Join(mainModVendor.Dir, "vendor"),
+	if vendorEnabled {
+		if mainModVendor != nil {
+			// Module vendor mode is on, so all the non-Main modules are irrelevant,
+			// and we need to search /vendor for everything.
+			r.mains = []*gocommand.ModuleJSON{mainModVendor}
+			r.dummyVendorMod = &gocommand.ModuleJSON{
+				Path: "",
+				Dir:  filepath.Join(mainModVendor.Dir, "vendor"),
+			}
+			r.modsByModPath = []*gocommand.ModuleJSON{mainModVendor, r.dummyVendorMod}
+			r.modsByDir = []*gocommand.ModuleJSON{mainModVendor, r.dummyVendorMod}
+		} else {
+			// Workspace vendor mode is on, so all the non-Main modules are irrelevant,
+			// and we need to search /vendor for everything.
+			r.mains = mainModsVendor
+			r.dummyVendorMod = &gocommand.ModuleJSON{
+				Path: "",
+				Dir:  filepath.Join(filepath.Dir(goWork), "vendor"),
+			}
+			r.modsByModPath = append(append([]*gocommand.ModuleJSON{}, mainModsVendor...), r.dummyVendorMod)
+			r.modsByDir = append(append([]*gocommand.ModuleJSON{}, mainModsVendor...), r.dummyVendorMod)
 		}
-		r.modsByModPath = []*gocommand.ModuleJSON{mainModVendor, r.dummyVendorMod}
-		r.modsByDir = []*gocommand.ModuleJSON{mainModVendor, r.dummyVendorMod}
 	} else {
 		// Vendor mode is off, so run go list -m ... to find everything.
 		err := r.initAllMods()
@@ -100,19 +160,14 @@ func (r *ModuleResolver) init() error {
 		// GO111MODULE=on. Other errors are fatal.
 		if err != nil {
 			if errMsg := err.Error(); !strings.Contains(errMsg, "working directory is not part of a module") && !strings.Contains(errMsg, "go.mod file not found") {
-				return err
+				return nil, err
 			}
 		}
 	}
 
-	if gmc := r.env.Env["GOMODCACHE"]; gmc != "" {
-		r.moduleCacheDir = gmc
-	} else {
-		gopaths := filepath.SplitList(goenv["GOPATH"])
-		if len(gopaths) == 0 {
-			return fmt.Errorf("empty GOPATH")
-		}
-		r.moduleCacheDir = filepath.Join(gopaths[0], "/pkg/mod")
+	r.moduleCacheDir = gomodcacheForEnv(goenv)
+	if r.moduleCacheDir == "" {
+		return nil, fmt.Errorf("cannot resolve GOMODCACHE")
 	}
 
 	sort.Slice(r.modsByModPath, func(i, j int) bool {
@@ -123,13 +178,14 @@ func (r *ModuleResolver) init() error {
 	})
 	sort.Slice(r.modsByDir, func(i, j int) bool {
 		count := func(x int) int {
-			return strings.Count(r.modsByDir[x].Dir, "/")
+			return strings.Count(r.modsByDir[x].Dir, string(filepath.Separator))
 		}
 		return count(j) < count(i) // descending order
 	})
 
-	r.roots = []gopathwalk.Root{
-		{Path: filepath.Join(goenv["GOROOT"], "/src"), Type: gopathwalk.RootGOROOT},
+	r.roots = []gopathwalk.Root{}
+	if goenv["GOROOT"] != "" { // "" happens in tests
+		r.roots = append(r.roots, gopathwalk.Root{Path: filepath.Join(goenv["GOROOT"], "/src"), Type: gopathwalk.RootGOROOT})
 	}
 	r.mainByDir = make(map[string]*gocommand.ModuleJSON)
 	for _, main := range r.mains {
@@ -141,7 +197,11 @@ func (r *ModuleResolver) init() error {
 	} else {
 		addDep := func(mod *gocommand.ModuleJSON) {
 			if mod.Replace == nil {
-				// This is redundant with the cache, but we'll skip it cheaply enough.
+				// This is redundant with the cache, but we'll skip it cheaply enough
+				// when we encounter it in the module cache scan.
+				//
+				// Including it at a lower index in r.roots than the module cache dir
+				// helps prioritize matches from within existing dependencies.
 				r.roots = append(r.roots, gopathwalk.Root{Path: mod.Dir, Type: gopathwalk.RootModuleCache})
 			} else {
 				r.roots = append(r.roots, gopathwalk.Root{Path: mod.Dir, Type: gopathwalk.RootOther})
@@ -158,24 +218,43 @@ func (r *ModuleResolver) init() error {
 				addDep(mod)
 			}
 		}
+		// If provided, share the moduleCacheCache.
+		//
+		// TODO(rfindley): The module cache is immutable. However, the loaded
+		// exports do depend on GOOS and GOARCH. Fortunately, the
+		// ProcessEnv.buildContext does not adjust these from build.DefaultContext
+		// (even though it should). So for now, this is OK to share, but we need to
+		// add logic for handling GOOS/GOARCH.
+		r.moduleCacheCache = moduleCacheCache
 		r.roots = append(r.roots, gopathwalk.Root{Path: r.moduleCacheDir, Type: gopathwalk.RootModuleCache})
 	}
 
 	r.scannedRoots = map[gopathwalk.Root]bool{}
 	if r.moduleCacheCache == nil {
-		r.moduleCacheCache = &dirInfoCache{
-			dirs:      map[string]*directoryPackageInfo{},
-			listeners: map[*int]cacheListener{},
-		}
+		r.moduleCacheCache = NewDirInfoCache()
 	}
-	if r.otherCache == nil {
-		r.otherCache = &dirInfoCache{
-			dirs:      map[string]*directoryPackageInfo{},
-			listeners: map[*int]cacheListener{},
-		}
+	r.otherCache = NewDirInfoCache()
+	return r, nil
+}
+
+// gomodcacheForEnv returns the GOMODCACHE value to use based on the given env
+// map, which must have GOMODCACHE and GOPATH populated.
+//
+// TODO(rfindley): this is defensive refactoring.
+//  1. Is this even relevant anymore? Can't we just read GOMODCACHE.
+//  2. Use this to separate module cache scanning from other scanning.
+func gomodcacheForEnv(goenv map[string]string) string {
+	if gmc := goenv["GOMODCACHE"]; gmc != "" {
+		// golang/go#67156: ensure that the module cache is clean, since it is
+		// assumed as a prefix to directories scanned by gopathwalk, which are
+		// themselves clean.
+		return filepath.Clean(gmc)
 	}
-	r.initialized = true
-	return nil
+	gopaths := filepath.SplitList(goenv["GOPATH"])
+	if len(gopaths) == 0 {
+		return ""
+	}
+	return filepath.Join(gopaths[0], "/pkg/mod")
 }
 
 func (r *ModuleResolver) initAllMods() error {
@@ -189,9 +268,7 @@ func (r *ModuleResolver) initAllMods() error {
 			return err
 		}
 		if mod.Dir == "" {
-			if r.env.Logf != nil {
-				r.env.Logf("module %v has not been downloaded and will be ignored", mod.Path)
-			}
+			r.env.logf("module %v has not been downloaded and will be ignored", mod.Path)
 			// Can't do anything with a module that's not downloaded.
 			continue
 		}
@@ -206,30 +283,86 @@ func (r *ModuleResolver) initAllMods() error {
 	return nil
 }
 
-func (r *ModuleResolver) ClearForNewScan() {
-	<-r.scanSema
-	r.scannedRoots = map[gopathwalk.Root]bool{}
-	r.otherCache = &dirInfoCache{
-		dirs:      map[string]*directoryPackageInfo{},
-		listeners: map[*int]cacheListener{},
-	}
-	r.scanSema <- struct{}{}
-}
+// ClearForNewScan invalidates the last scan.
+//
+// It preserves the set of roots, but forgets about the set of directories.
+// Though it forgets the set of module cache directories, it remembers their
+// contents, since they are assumed to be immutable.
+func (r *ModuleResolver) ClearForNewScan() Resolver {
+	<-r.scanSema // acquire r, to guard scannedRoots
+	r2 := &ModuleResolver{
+		env:            r.env,
+		dummyVendorMod: r.dummyVendorMod,
+		moduleCacheDir: r.moduleCacheDir,
+		roots:          r.roots,
+		mains:          r.mains,
+		mainByDir:      r.mainByDir,
+		modsByModPath:  r.modsByModPath,
 
-func (r *ModuleResolver) ClearForNewMod() {
-	<-r.scanSema
-	*r = ModuleResolver{
-		env:              r.env,
+		scanSema:         make(chan struct{}, 1),
+		scannedRoots:     make(map[gopathwalk.Root]bool),
+		otherCache:       NewDirInfoCache(),
 		moduleCacheCache: r.moduleCacheCache,
-		otherCache:       r.otherCache,
-		scanSema:         r.scanSema,
 	}
-	r.init()
-	r.scanSema <- struct{}{}
+	r2.scanSema <- struct{}{} // r2 must start released
+	// Invalidate root scans. We don't need to invalidate module cache roots,
+	// because they are immutable.
+	// (We don't support a use case where GOMODCACHE is cleaned in the middle of
+	// e.g. a gopls session: the user must restart gopls to get accurate
+	// imports.)
+	//
+	// Scanning for new directories in GOMODCACHE should be handled elsewhere,
+	// via a call to ScanModuleCache.
+	for _, root := range r.roots {
+		if root.Type == gopathwalk.RootModuleCache && r.scannedRoots[root] {
+			r2.scannedRoots[root] = true
+		}
+	}
+	r.scanSema <- struct{}{} // release r
+	return r2
 }
 
-// findPackage returns the module and directory that contains the package at
-// the given import path, or returns nil, "" if no module is in scope.
+// ClearModuleInfo invalidates resolver state that depends on go.mod file
+// contents (essentially, the output of go list -m -json ...).
+//
+// Notably, it does not forget directory contents, which are reset
+// asynchronously via ClearForNewScan.
+//
+// If the ProcessEnv is a GOPATH environment, ClearModuleInfo is a no op.
+//
+// TODO(rfindley): move this to a new env.go, consolidating ProcessEnv methods.
+func (e *ProcessEnv) ClearModuleInfo() {
+	if r, ok := e.resolver.(*ModuleResolver); ok {
+		resolver, err := newModuleResolver(e, e.ModCache)
+		if err != nil {
+			e.resolver = nil
+			e.resolverErr = err
+			return
+		}
+
+		<-r.scanSema // acquire (guards caches)
+		resolver.moduleCacheCache = r.moduleCacheCache
+		resolver.otherCache = r.otherCache
+		r.scanSema <- struct{}{} // release
+
+		e.UpdateResolver(resolver)
+	}
+}
+
+// UpdateResolver sets the resolver for the ProcessEnv to use in imports
+// operations. Only for use with the result of [Resolver.ClearForNewScan].
+//
+// TODO(rfindley): this awkward API is a result of the (arguably) inverted
+// relationship between configuration and state described in the doc comment
+// for [ProcessEnv].
+func (e *ProcessEnv) UpdateResolver(r Resolver) {
+	e.resolver = r
+	e.resolverErr = nil
+}
+
+// findPackage returns the module and directory from within the main modules
+// and their dependencies that contains the package at the given import path,
+// or returns nil, "" if no module is in scope.
 func (r *ModuleResolver) findPackage(importPath string) (*gocommand.ModuleJSON, string) {
 	// This can't find packages in the stdlib, but that's harmless for all
 	// the existing code paths.
@@ -264,7 +397,7 @@ func (r *ModuleResolver) findPackage(importPath string) (*gocommand.ModuleJSON,
 		}
 
 		// Not cached. Read the filesystem.
-		pkgFiles, err := ioutil.ReadDir(pkgDir)
+		pkgFiles, err := os.ReadDir(pkgDir)
 		if err != nil {
 			continue
 		}
@@ -295,10 +428,6 @@ func (r *ModuleResolver) cacheStore(info directoryPackageInfo) {
 	}
 }
 
-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) (string, error) {
 	if info.rootType == gopathwalk.RootModuleCache {
@@ -307,7 +436,7 @@ func (r *ModuleResolver) cachePackageName(info directoryPackageInfo) (string, er
 	return r.otherCache.CachePackageName(info)
 }
 
-func (r *ModuleResolver) cacheExports(ctx context.Context, env *ProcessEnv, info directoryPackageInfo) (string, []string, error) {
+func (r *ModuleResolver) cacheExports(ctx context.Context, env *ProcessEnv, info directoryPackageInfo) (string, []stdlib.Symbol, error) {
 	if info.rootType == gopathwalk.RootModuleCache {
 		return r.moduleCacheCache.CacheExports(ctx, env, info)
 	}
@@ -327,6 +456,10 @@ func (r *ModuleResolver) findModuleByDir(dir string) *gocommand.ModuleJSON {
 	// - in /vendor/ in -mod=vendor mode.
 	//    - nested module? Dunno.
 	// Rumor has it that replace targets cannot contain other replace targets.
+	//
+	// Note that it is critical here that modsByDir is sorted to have deeper dirs
+	// first. This ensures that findModuleByDir finds the innermost module.
+	// See also golang/go#56291.
 	for _, m := range r.modsByDir {
 		if !strings.HasPrefix(dir, m.Dir) {
 			continue
@@ -363,15 +496,15 @@ func (r *ModuleResolver) dirIsNestedModule(dir string, mod *gocommand.ModuleJSON
 	return modDir != mod.Dir
 }
 
-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)
+func readModName(modFile string) string {
+	modBytes, err := os.ReadFile(modFile)
+	if err != nil {
+		return ""
 	}
+	return modulePath(modBytes)
+}
 
+func (r *ModuleResolver) modInfo(dir string) (modDir, modName string) {
 	if r.dirInModuleCache(dir) {
 		if matches := modCacheRegexp.FindStringSubmatch(dir); len(matches) == 3 {
 			index := strings.Index(dir, matches[1]+"@"+matches[2])
@@ -405,11 +538,9 @@ func (r *ModuleResolver) dirInModuleCache(dir string) bool {
 }
 
 func (r *ModuleResolver) loadPackageNames(importPaths []string, srcDir string) (map[string]string, error) {
-	if err := r.init(); err != nil {
-		return nil, err
-	}
 	names := map[string]string{}
 	for _, path := range importPaths {
+		// TODO(rfindley): shouldn't this use the dirInfoCache?
 		_, packageDir := r.findPackage(path)
 		if packageDir == "" {
 			continue
@@ -424,9 +555,8 @@ func (r *ModuleResolver) loadPackageNames(importPaths []string, srcDir string) (
 }
 
 func (r *ModuleResolver) scan(ctx context.Context, callback *scanCallback) error {
-	if err := r.init(); err != nil {
-		return err
-	}
+	ctx, done := event.Start(ctx, "imports.ModuleResolver.scan")
+	defer done()
 
 	processDir := func(info directoryPackageInfo) {
 		// Skip this directory if we were not able to get the package information successfully.
@@ -437,18 +567,18 @@ func (r *ModuleResolver) scan(ctx context.Context, callback *scanCallback) error
 		if err != nil {
 			return
 		}
-
 		if !callback.dirFound(pkg) {
 			return
 		}
+
 		pkg.packageName, err = r.cachePackageName(info)
 		if err != nil {
 			return
 		}
-
 		if !callback.packageNameLoaded(pkg) {
 			return
 		}
+
 		_, exports, err := r.loadExports(ctx, pkg, false)
 		if err != nil {
 			return
@@ -487,7 +617,6 @@ func (r *ModuleResolver) scan(ctx context.Context, callback *scanCallback) error
 		return packageScanned
 	}
 
-	// Add anything new to the cache, and process it if we're still listening.
 	add := func(root gopathwalk.Root, dir string) {
 		r.cacheStore(r.scanDirForPackage(root, dir))
 	}
@@ -502,9 +631,9 @@ func (r *ModuleResolver) scan(ctx context.Context, callback *scanCallback) error
 		select {
 		case <-ctx.Done():
 			return
-		case <-r.scanSema:
+		case <-r.scanSema: // acquire
 		}
-		defer func() { r.scanSema <- struct{}{} }()
+		defer func() { r.scanSema <- struct{}{} }() // release
 		// We have the lock on r.scannedRoots, and no other scans can run.
 		for _, root := range roots {
 			if ctx.Err() != nil {
@@ -527,7 +656,7 @@ func (r *ModuleResolver) scan(ctx context.Context, callback *scanCallback) error
 }
 
 func (r *ModuleResolver) scoreImportPath(ctx context.Context, path string) float64 {
-	if _, ok := stdlib[path]; ok {
+	if stdlib.HasPackage(path) {
 		return MaxRelevance
 	}
 	mod, _ := r.findPackage(path)
@@ -605,10 +734,7 @@ func (r *ModuleResolver) canonicalize(info directoryPackageInfo) (*pkg, error) {
 	return res, nil
 }
 
-func (r *ModuleResolver) loadExports(ctx context.Context, pkg *pkg, includeTest bool) (string, []string, error) {
-	if err := r.init(); err != nil {
-		return "", nil, err
-	}
+func (r *ModuleResolver) loadExports(ctx context.Context, pkg *pkg, includeTest bool) (string, []stdlib.Symbol, error) {
 	if info, ok := r.cacheLoad(pkg.dir); ok && !includeTest {
 		return r.cacheExports(ctx, r.env, info)
 	}
@@ -617,8 +743,8 @@ func (r *ModuleResolver) loadExports(ctx context.Context, pkg *pkg, includeTest
 
 func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) directoryPackageInfo {
 	subdir := ""
-	if dir != root.Path {
-		subdir = dir[len(root.Path)+len("/"):]
+	if prefix := root.Path + string(filepath.Separator); strings.HasPrefix(dir, prefix) {
+		subdir = dir[len(prefix):]
 	}
 	importPath := filepath.ToSlash(subdir)
 	if strings.HasPrefix(importPath, "vendor/") {
@@ -641,9 +767,7 @@ func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) dir
 		}
 		modPath, err := module.UnescapePath(filepath.ToSlash(matches[1]))
 		if err != nil {
-			if r.env.Logf != nil {
-				r.env.Logf("decoding module cache path %q: %v", subdir, err)
-			}
+			r.env.logf("decoding module cache path %q: %v", subdir, err)
 			return directoryPackageInfo{
 				status: directoryScanned,
 				err:    fmt.Errorf("decoding module cache path %q: %v", subdir, err),

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

@@ -7,12 +7,17 @@ package imports
 import (
 	"context"
 	"fmt"
+	"path"
+	"path/filepath"
+	"strings"
 	"sync"
 
+	"golang.org/x/mod/module"
 	"golang.org/x/tools/internal/gopathwalk"
+	"golang.org/x/tools/internal/stdlib"
 )
 
-// To find packages to import, the resolver needs to know about all of the
+// To find packages to import, the resolver needs to know about all of
 // the packages that could be imported. This includes packages that are
 // already in modules that are in (1) the current module, (2) replace targets,
 // and (3) packages in the module cache. Packages in (1) and (2) may change over
@@ -39,6 +44,8 @@ const (
 	exportsLoaded
 )
 
+// directoryPackageInfo holds (possibly incomplete) information about packages
+// contained in a given directory.
 type directoryPackageInfo struct {
 	// status indicates the extent to which this struct has been filled in.
 	status directoryPackageStatus
@@ -63,8 +70,11 @@ type directoryPackageInfo struct {
 	packageName string // the package name, as declared in the source.
 
 	// Set when status >= exportsLoaded.
-
-	exports []string
+	// TODO(rfindley): it's hard to see this, but exports depend implicitly on
+	// the default build context GOOS and GOARCH.
+	//
+	// We can make this explicit, and key exports by GOOS, GOARCH.
+	exports []stdlib.Symbol
 }
 
 // reachedStatus returns true when info has a status at least target and any error associated with
@@ -79,7 +89,7 @@ func (info *directoryPackageInfo) reachedStatus(target directoryPackageStatus) (
 	return true, nil
 }
 
-// dirInfoCache is a concurrency safe map for storing information about
+// 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.
@@ -92,21 +102,26 @@ func (info *directoryPackageInfo) reachedStatus(target directoryPackageStatus) (
 // 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 dirInfoCache struct {
+type DirInfoCache struct {
 	mu sync.Mutex
 	// dirs stores information about packages in directories, keyed by absolute path.
 	dirs      map[string]*directoryPackageInfo
 	listeners map[*int]cacheListener
 }
 
+func NewDirInfoCache() *DirInfoCache {
+	return &DirInfoCache{
+		dirs:      make(map[string]*directoryPackageInfo),
+		listeners: make(map[*int]cacheListener),
+	}
+}
+
 type cacheListener func(directoryPackageInfo)
 
 // ScanAndListen calls listener on all the items in the cache, and on anything
 // newly added. The returned stop function waits for all in-flight callbacks to
 // finish and blocks new ones.
-func (d *dirInfoCache) ScanAndListen(ctx context.Context, listener cacheListener) func() {
+func (d *DirInfoCache) ScanAndListen(ctx context.Context, listener cacheListener) func() {
 	ctx, cancel := context.WithCancel(ctx)
 
 	// Flushing out all the callbacks is tricky without knowing how many there
@@ -162,8 +177,10 @@ func (d *dirInfoCache) ScanAndListen(ctx context.Context, listener cacheListener
 }
 
 // Store stores the package info for dir.
-func (d *dirInfoCache) Store(dir string, info directoryPackageInfo) {
+func (d *DirInfoCache) Store(dir string, info directoryPackageInfo) {
 	d.mu.Lock()
+	// TODO(rfindley, golang/go#59216): should we overwrite an existing entry?
+	// That seems incorrect as the cache should be idempotent.
 	_, old := d.dirs[dir]
 	d.dirs[dir] = &info
 	var listeners []cacheListener
@@ -180,7 +197,7 @@ func (d *dirInfoCache) Store(dir string, info directoryPackageInfo) {
 }
 
 // Load returns a copy of the directoryPackageInfo for absolute directory dir.
-func (d *dirInfoCache) Load(dir string) (directoryPackageInfo, bool) {
+func (d *DirInfoCache) Load(dir string) (directoryPackageInfo, bool) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 	info, ok := d.dirs[dir]
@@ -191,7 +208,7 @@ func (d *dirInfoCache) Load(dir string) (directoryPackageInfo, bool) {
 }
 
 // Keys returns the keys currently present in d.
-func (d *dirInfoCache) Keys() (keys []string) {
+func (d *DirInfoCache) Keys() (keys []string) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 	for key := range d.dirs {
@@ -200,7 +217,7 @@ func (d *dirInfoCache) Keys() (keys []string) {
 	return keys
 }
 
-func (d *dirInfoCache) CachePackageName(info directoryPackageInfo) (string, error) {
+func (d *DirInfoCache) CachePackageName(info directoryPackageInfo) (string, error) {
 	if loaded, err := info.reachedStatus(nameLoaded); loaded {
 		return info.packageName, err
 	}
@@ -213,7 +230,7 @@ func (d *dirInfoCache) CachePackageName(info directoryPackageInfo) (string, erro
 	return info.packageName, info.err
 }
 
-func (d *dirInfoCache) CacheExports(ctx context.Context, env *ProcessEnv, info directoryPackageInfo) (string, []string, error) {
+func (d *DirInfoCache) CacheExports(ctx context.Context, env *ProcessEnv, info directoryPackageInfo) (string, []stdlib.Symbol, error) {
 	if reached, _ := info.reachedStatus(exportsLoaded); reached {
 		return info.packageName, info.exports, info.err
 	}
@@ -234,3 +251,81 @@ func (d *dirInfoCache) CacheExports(ctx context.Context, env *ProcessEnv, info d
 	d.Store(info.dir, info)
 	return info.packageName, info.exports, info.err
 }
+
+// ScanModuleCache walks the given directory, which must be a GOMODCACHE value,
+// for directory package information, storing the results in cache.
+func ScanModuleCache(dir string, cache *DirInfoCache, logf func(string, ...any)) {
+	// Note(rfindley): it's hard to see, but this function attempts to implement
+	// just the side effects on cache of calling PrimeCache with a ProcessEnv
+	// that has the given dir as its GOMODCACHE.
+	//
+	// Teasing out the control flow, we see that we can avoid any handling of
+	// vendor/ and can infer module info entirely from the path, simplifying the
+	// logic here.
+
+	root := gopathwalk.Root{
+		Path: filepath.Clean(dir),
+		Type: gopathwalk.RootModuleCache,
+	}
+
+	directoryInfo := func(root gopathwalk.Root, dir string) directoryPackageInfo {
+		// This is a copy of ModuleResolver.scanDirForPackage, trimmed down to
+		// logic that applies to a module cache directory.
+
+		subdir := ""
+		if dir != root.Path {
+			subdir = dir[len(root.Path)+len("/"):]
+		}
+
+		matches := modCacheRegexp.FindStringSubmatch(subdir)
+		if len(matches) == 0 {
+			return directoryPackageInfo{
+				status: directoryScanned,
+				err:    fmt.Errorf("invalid module cache path: %v", subdir),
+			}
+		}
+		modPath, err := module.UnescapePath(filepath.ToSlash(matches[1]))
+		if err != nil {
+			if logf != nil {
+				logf("decoding module cache path %q: %v", subdir, err)
+			}
+			return directoryPackageInfo{
+				status: directoryScanned,
+				err:    fmt.Errorf("decoding module cache path %q: %v", subdir, err),
+			}
+		}
+		importPath := path.Join(modPath, filepath.ToSlash(matches[3]))
+		index := strings.Index(dir, matches[1]+"@"+matches[2])
+		modDir := filepath.Join(dir[:index], matches[1]+"@"+matches[2])
+		modName := readModName(filepath.Join(modDir, "go.mod"))
+		return directoryPackageInfo{
+			status:                 directoryScanned,
+			dir:                    dir,
+			rootType:               root.Type,
+			nonCanonicalImportPath: importPath,
+			moduleDir:              modDir,
+			moduleName:             modName,
+		}
+	}
+
+	add := func(root gopathwalk.Root, dir string) {
+		info := directoryInfo(root, dir)
+		cache.Store(info.dir, info)
+	}
+
+	skip := func(_ gopathwalk.Root, dir string) bool {
+		// Skip directories that have already been scanned.
+		//
+		// Note that gopathwalk only adds "package" directories, which must contain
+		// a .go file, and all such package directories in the module cache are
+		// immutable. So if we can load a dir, it can be skipped.
+		info, ok := cache.Load(dir)
+		if !ok {
+			return false
+		}
+		packageScanned, _ := info.reachedStatus(directoryScanned)
+		return packageScanned
+	}
+
+	gopathwalk.WalkSkip([]gopathwalk.Root{root}, add, skip, gopathwalk.Options{Logf: logf, ModulesEnabled: true})
+}

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

@@ -18,7 +18,7 @@ import (
 // sortImports sorts runs of consecutive import lines in import blocks in f.
 // It also removes duplicate imports when it is possible to do so without data loss.
 //
-// It may mutate the token.File.
+// It may mutate the token.File and the ast.File.
 func sortImports(localPrefix string, tokFile *token.File, f *ast.File) {
 	for i, d := range f.Decls {
 		d, ok := d.(*ast.GenDecl)