src

mod.go (26549B)

---

 // 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 imports
 
 import (
 	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
 	"os"
 	"path"
 	"path/filepath"
 	"regexp"
 	"slices"
 	"sort"
 	"strconv"
 	"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"
 )
 
 // 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
 
 	// 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.
 
 	// 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
 }
 
 // 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{}{} // release
 
 	goenv, err := r.env.goEnv()
 	if err != nil {
 		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,
 		Env:        r.env.env(),
 		Logf:       r.env.Logf,
 		WorkingDir: r.env.WorkingDir,
 	}
 
 	vendorEnabled := false
 	var mainModVendor *gocommand.ModuleJSON    // for module vendoring
 	var mainModsVendor []*gocommand.ModuleJSON // for workspace vendoring
 
 	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 nil, err
 		}
 	} else {
 		vendorEnabled, mainModsVendor, err = gocommand.WorkspaceVendorEnabled(context.Background(), inv, r.env.GocmdRunner)
 		if err != nil {
 			return nil, err
 		}
 	}
 
 	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(slices.Clone(mainModsVendor), r.dummyVendorMod)
 			r.modsByDir = append(slices.Clone(mainModsVendor), r.dummyVendorMod)
 		}
 	} else {
 		// Vendor mode is off, so run go list -m ... to find everything.
 		err := r.initAllMods()
 		// We expect an error when running outside of a module with
 		// 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 nil, err
 			}
 		}
 	}
 
 	r.moduleCacheDir = goenv["GOMODCACHE"]
 
 	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, string(filepath.Separator))
 		}
 		return count(j) < count(i) // descending order
 	})
 
 	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 {
 		r.roots = append(r.roots, gopathwalk.Root{Path: main.Dir, Type: gopathwalk.RootCurrentModule})
 		r.mainByDir[main.Dir] = main
 	}
 	if vendorEnabled {
 		r.roots = append(r.roots, gopathwalk.Root{Path: r.dummyVendorMod.Dir, Type: gopathwalk.RootOther})
 	} else {
 		addDep := func(mod *gocommand.ModuleJSON) {
 			if mod.Replace == nil {
 				// 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})
 			}
 		}
 		// Walk dependent modules before scanning the full mod cache, direct deps first.
 		for _, mod := range r.modsByModPath {
 			if !mod.Indirect && !mod.Main {
 				addDep(mod)
 			}
 		}
 		for _, mod := range r.modsByModPath {
 			if mod.Indirect && !mod.Main {
 				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 = NewDirInfoCache()
 	}
 	r.otherCache = NewDirInfoCache()
 	return r, nil
 }
 
 func (r *ModuleResolver) initAllMods() error {
 	stdout, err := r.env.invokeGo(context.TODO(), "list", "-m", "-e", "-json", "...")
 	if err != nil {
 		return err
 	}
 	for dec := json.NewDecoder(stdout); dec.More(); {
 		mod := &gocommand.ModuleJSON{}
 		if err := dec.Decode(mod); err != nil {
 			return err
 		}
 		if mod.Dir == "" {
 			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
 		}
 		// golang/go#36193: the go command doesn't always clean paths.
 		mod.Dir = filepath.Clean(mod.Dir)
 		r.modsByModPath = append(r.modsByModPath, mod)
 		r.modsByDir = append(r.modsByDir, mod)
 		if mod.Main {
 			r.mains = append(r.mains, mod)
 		}
 	}
 	return nil
 }
 
 // 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,
 
 		scanSema:         make(chan struct{}, 1),
 		scannedRoots:     make(map[gopathwalk.Root]bool),
 		otherCache:       NewDirInfoCache(),
 		moduleCacheCache: r.moduleCacheCache,
 	}
 	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
 }
 
 // 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.
 	for _, m := range r.modsByModPath {
 		if !strings.HasPrefix(importPath, m.Path) {
 			continue
 		}
 		pathInModule := importPath[len(m.Path):]
 		pkgDir := filepath.Join(m.Dir, pathInModule)
 		if r.dirIsNestedModule(pkgDir, m) {
 			continue
 		}
 
 		if info, ok := r.cacheLoad(pkgDir); ok {
 			if loaded, err := info.reachedStatus(nameLoaded); loaded {
 				if err != nil {
 					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 := os.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.
 		for _, fi := range pkgFiles {
 			if ok, _ := r.env.matchFile(pkgDir, fi.Name()); ok {
 				return m, pkgDir
 			}
 		}
 	}
 	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)
 	}
 }
 
 // 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 {
 		return r.moduleCacheCache.CachePackageName(info)
 	}
 	return r.otherCache.CachePackageName(info)
 }
 
 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)
 	}
 	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) *gocommand.ModuleJSON {
 	// This is quite tricky and may not be correct. dir could be:
 	// - a package in the main module.
 	// - a replace target underneath the main module's directory.
 	//    - a nested module in the above.
 	// - a replace target somewhere totally random.
 	//    - a nested module in the above.
 	// - in the mod cache.
 	// - 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
 		}
 
 		if r.dirIsNestedModule(dir, m) {
 			continue
 		}
 
 		return m
 	}
 	return nil
 }
 
 // dirIsNestedModule reports if dir is contained in a nested module underneath
 // mod, not actually in mod.
 func (r *ModuleResolver) dirIsNestedModule(dir string, mod *gocommand.ModuleJSON) bool {
 	if !strings.HasPrefix(dir, mod.Dir) {
 		return false
 	}
 	if r.dirInModuleCache(dir) {
 		// Nested modules in the module cache are pruned,
 		// so it cannot be a nested module.
 		return false
 	}
 	if mod != nil && mod == r.dummyVendorMod {
 		// The /vendor pseudomodule is flattened and doesn't actually count.
 		return false
 	}
 	modDir, _ := r.modInfo(dir)
 	if modDir == "" {
 		return false
 	}
 	return modDir != mod.Dir
 }
 
 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])
 			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 dir, readModName(f)
 		}
 
 		d := filepath.Dir(dir)
 		if len(d) >= len(dir) {
 			return "", "" // reached top of file system, no go.mod
 		}
 		dir = d
 	}
 }
 
 func (r *ModuleResolver) dirInModuleCache(dir string) bool {
 	if r.moduleCacheDir == "" {
 		return false
 	}
 	return strings.HasPrefix(dir, r.moduleCacheDir)
 }
 
 func (r *ModuleResolver) loadPackageNames(importPaths []string, srcDir string) (map[string]string, error) {
 	names := map[string]string{}
 	for _, path := range importPaths {
 		// TODO(rfindley): shouldn't this use the dirInfoCache?
 		_, packageDir := r.findPackage(path)
 		if packageDir == "" {
 			continue
 		}
 		name, err := packageDirToName(packageDir)
 		if err != nil {
 			continue
 		}
 		names[path] = name
 	}
 	return names, nil
 }
 
 func (r *ModuleResolver) scan(ctx context.Context, callback *scanCallback) error {
 	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.
 		if scanned, err := info.reachedStatus(directoryScanned); !scanned || err != nil {
 			return
 		}
 		pkg, err := r.canonicalize(info)
 		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
 		}
 		callback.exportsLoaded(pkg, exports)
 	}
 
 	// Start processing everything in the cache, and listen for the new stuff
 	// we discover in the walk below.
 	stop1 := r.moduleCacheCache.ScanAndListen(ctx, processDir)
 	defer stop1()
 	stop2 := r.otherCache.ScanAndListen(ctx, processDir)
 	defer stop2()
 
 	// We assume cached directories are fully cached, including all their
 	// children, and have not changed. We can skip them.
 	skip := func(root gopathwalk.Root, dir string) bool {
 		if r.env.SkipPathInScan != nil && root.Type == gopathwalk.RootCurrentModule {
 			if root.Path == dir {
 				return false
 			}
 
 			if r.env.SkipPathInScan(filepath.Clean(dir)) {
 				return true
 			}
 		}
 
 		info, ok := r.cacheLoad(dir)
 		if !ok {
 			return false
 		}
 		// This directory can be skipped as long as we have already scanned it.
 		// Packages with errors will continue to have errors, so there is no need
 		// to rescan them.
 		packageScanned, _ := info.reachedStatus(directoryScanned)
 		return packageScanned
 	}
 
 	add := func(root gopathwalk.Root, dir string) {
 		r.cacheStore(r.scanDirForPackage(root, dir))
 	}
 
 	// r.roots and the callback are not necessarily safe to use in the
 	// goroutine below. Process them eagerly.
 	roots := filterRoots(r.roots, callback.rootFound)
 	// We can't cancel walks, because we need them to finish to have a usable
 	// cache. Instead, run them in a separate goroutine and detach.
 	scanDone := make(chan struct{})
 	go func() {
 		select {
 		case <-ctx.Done():
 			return
 		case <-r.scanSema: // acquire
 		}
 		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 {
 				return
 			}
 
 			if r.scannedRoots[root] {
 				continue
 			}
 			gopathwalk.WalkSkip([]gopathwalk.Root{root}, add, skip, gopathwalk.Options{Logf: r.env.Logf, ModulesEnabled: true})
 			r.scannedRoots[root] = true
 		}
 		close(scanDone)
 	}()
 	select {
 	case <-ctx.Done():
 	case <-scanDone:
 	}
 	return nil
 }
 
 func (r *ModuleResolver) scoreImportPath(ctx context.Context, path string) float64 {
 	if stdlib.HasPackage(path) {
 		return MaxRelevance
 	}
 	mod, _ := r.findPackage(path)
 	return modRelevance(mod)
 }
 
 func modRelevance(mod *gocommand.ModuleJSON) float64 {
 	var relevance float64
 	switch {
 	case mod == nil: // out of scope
 		return MaxRelevance - 4
 	case mod.Indirect:
 		relevance = MaxRelevance - 3
 	case !mod.Main:
 		relevance = MaxRelevance - 2
 	default:
 		relevance = MaxRelevance - 1 // main module ties with stdlib
 	}
 
 	_, versionString, ok := module.SplitPathVersion(mod.Path)
 	if ok {
 		_, after, ok := strings.Cut(versionString, "v")
 		if !ok {
 			return relevance
 		}
 		if versionNumber, err := strconv.ParseFloat(after, 64); err == nil {
 			relevance += versionNumber / 1000
 		}
 	}
 
 	return relevance
 }
 
 // canonicalize gets the result of canonicalizing the packages using the results
 // of initializing the resolver from 'go list -m'.
 func (r *ModuleResolver) canonicalize(info directoryPackageInfo) (*pkg, error) {
 	// Packages in GOROOT are already canonical, regardless of the std/cmd modules.
 	if info.rootType == gopathwalk.RootGOROOT {
 		return &pkg{
 			importPathShort: info.nonCanonicalImportPath,
 			dir:             info.dir,
 			packageName:     path.Base(info.nonCanonicalImportPath),
 			relevance:       MaxRelevance,
 		}, nil
 	}
 
 	importPath := info.nonCanonicalImportPath
 	mod := r.findModuleByDir(info.dir)
 	// Check if the directory is underneath a module that's in scope.
 	if mod != nil {
 		// It is. If dir is the target of a replace directive,
 		// our guessed import path is wrong. Use the real one.
 		if mod.Dir == info.dir {
 			importPath = mod.Path
 		} else {
 			dirInMod := info.dir[len(mod.Dir)+len("/"):]
 			importPath = path.Join(mod.Path, filepath.ToSlash(dirInMod))
 		}
 	} else if !strings.HasPrefix(importPath, info.moduleName) {
 		// The module's name doesn't match the package's import path. It
 		// probably needs a replace directive we don't have.
 		return nil, fmt.Errorf("package in %q is not valid without a replace statement", info.dir)
 	}
 
 	res := &pkg{
 		importPathShort: importPath,
 		dir:             info.dir,
 		relevance:       modRelevance(mod),
 	}
 	// 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 != "" {
 		res.dir = canonicalDir
 	}
 	return res, nil
 }
 
 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)
 	}
 	return loadExportsFromFiles(ctx, r.env, pkg.dir, includeTest)
 }
 
 func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) directoryPackageInfo {
 	subdir := ""
 	if prefix := root.Path + string(filepath.Separator); strings.HasPrefix(dir, prefix) {
 		subdir = dir[len(prefix):]
 	}
 	importPath := filepath.ToSlash(subdir)
 	if strings.HasPrefix(importPath, "vendor/") {
 		// 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:
 		importPath = path.Join(r.mainByDir[root.Path].Path, filepath.ToSlash(subdir))
 	case gopathwalk.RootModuleCache:
 		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 {
 			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),
 			}
 		}
 		importPath = path.Join(modPath, filepath.ToSlash(matches[3]))
 	}
 
 	modDir, modName := r.modInfo(dir)
 	result := directoryPackageInfo{
 		status:                 directoryScanned,
 		dir:                    dir,
 		rootType:               root.Type,
 		nonCanonicalImportPath: importPath,
 		moduleDir:              modDir,
 		moduleName:             modName,
 	}
 	if root.Type == gopathwalk.RootGOROOT {
 		// stdlib packages are always in scope, despite the confusing go.mod
 		return result
 	}
 	return result
 }
 
 // modCacheRegexp splits a path in a module cache into module, module version, and package.
 var modCacheRegexp = regexp.MustCompile(`(.*)@([^/\\]*)(.*)`)
 
 var (
 	slashSlash = []byte("//")
 	moduleStr  = []byte("module")
 )
 
 // modulePath returns the module path from the gomod file text.
 // If it cannot find a module path, it returns an empty string.
 // It is tolerant of unrelated problems in the go.mod file.
 //
 // Copied from cmd/go/internal/modfile.
 func modulePath(mod []byte) string {
 	for len(mod) > 0 {
 		line := mod
 		mod = nil
 		if i := bytes.IndexByte(line, '\n'); i >= 0 {
 			line, mod = line[:i], line[i+1:]
 		}
 		if i := bytes.Index(line, slashSlash); i >= 0 {
 			line = line[:i]
 		}
 		line = bytes.TrimSpace(line)
 		if !bytes.HasPrefix(line, moduleStr) {
 			continue
 		}
 		line = line[len(moduleStr):]
 		n := len(line)
 		line = bytes.TrimSpace(line)
 		if len(line) == n || len(line) == 0 {
 			continue
 		}
 
 		if line[0] == '"' || line[0] == '`' {
 			p, err := strconv.Unquote(string(line))
 			if err != nil {
 				return "" // malformed quoted string or multiline module path
 			}
 			return p
 		}
 
 		return string(line)
 	}
 	return "" // missing module path
 }