Vendor copies of x/tools/imports, cmd/api packages.

Author: dmitshur

playground/internal/imports/fix.go

@@ -0,0 +1,387 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package imports
+
+import (
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"sync"
+
+	"golang.org/x/tools/go/ast/astutil"
+)
+
+// importToGroup is a list of functions which map from an import path to
+// a group number.
+var importToGroup = []func(importPath string) (num int, ok bool){
+	func(importPath string) (num int, ok bool) {
+		if strings.HasPrefix(importPath, "appengine") {
+			return 2, true
+		}
+		return
+	},
+	func(importPath string) (num int, ok bool) {
+		if strings.Contains(importPath, ".") {
+			return 1, true
+		}
+		return
+	},
+}
+
+func importGroup(importPath string) int {
+	for _, fn := range importToGroup {
+		if n, ok := fn(importPath); ok {
+			return n
+		}
+	}
+	return 0
+}
+
+func fixImports(fset *token.FileSet, f *ast.File) (added []string, err error) {
+	// refs are a set of possible package references currently unsatisfied by imports.
+	// first key: either base package (e.g. "fmt") or renamed package
+	// second key: referenced package symbol (e.g. "Println")
+	refs := make(map[string]map[string]bool)
+
+	// decls are the current package imports. key is base package or renamed package.
+	decls := make(map[string]*ast.ImportSpec)
+
+	// collect potential uses of packages.
+	var visitor visitFn
+	visitor = visitFn(func(node ast.Node) ast.Visitor {
+		if node == nil {
+			return visitor
+		}
+		switch v := node.(type) {
+		case *ast.ImportSpec:
+			if v.Name != nil {
+				decls[v.Name.Name] = v
+			} else {
+				local := importPathToName(strings.Trim(v.Path.Value, `\"`))
+				decls[local] = v
+			}
+		case *ast.SelectorExpr:
+			xident, ok := v.X.(*ast.Ident)
+			if !ok {
+				break
+			}
+			if xident.Obj != nil {
+				// if the parser can resolve it, it's not a package ref
+				break
+			}
+			pkgName := xident.Name
+			if refs[pkgName] == nil {
+				refs[pkgName] = make(map[string]bool)
+			}
+			if decls[pkgName] == nil {
+				refs[pkgName][v.Sel.Name] = true
+			}
+		}
+		return visitor
+	})
+	ast.Walk(visitor, f)
+
+	// Nil out any unused ImportSpecs, to be removed in following passes
+	unusedImport := map[string]bool{}
+	for pkg, is := range decls {
+		if refs[pkg] == nil && pkg != "_" && pkg != "." {
+			unusedImport[strings.Trim(is.Path.Value, `"`)] = true
+		}
+	}
+	for ipath := range unusedImport {
+		if ipath == "C" {
+			// Don't remove cgo stuff.
+			continue
+		}
+		astutil.DeleteImport(fset, f, ipath)
+	}
+
+	// Search for imports matching potential package references.
+	searches := 0
+	type result struct {
+		ipath string
+		name  string
+		err   error
+	}
+	results := make(chan result)
+	for pkgName, symbols := range refs {
+		if len(symbols) == 0 {
+			continue // skip over packages already imported
+		}
+		go func(pkgName string, symbols map[string]bool) {
+			ipath, rename, err := findImport(pkgName, symbols)
+			r := result{ipath: ipath, err: err}
+			if rename {
+				r.name = pkgName
+			}
+			results <- r
+		}(pkgName, symbols)
+		searches++
+	}
+	for i := 0; i < searches; i++ {
+		result := <-results
+		if result.err != nil {
+			return nil, result.err
+		}
+		if result.ipath != "" {
+			if result.name != "" {
+				astutil.AddNamedImport(fset, f, result.name, result.ipath)
+			} else {
+				astutil.AddImport(fset, f, result.ipath)
+			}
+			added = append(added, result.ipath)
+		}
+	}
+
+	return added, nil
+}
+
+// importPathToName returns the package name for the given import path.
+var importPathToName = importPathToNameGoPath
+
+// importPathToNameBasic assumes the package name is the base of import path.
+func importPathToNameBasic(importPath string) (packageName string) {
+	return path.Base(importPath)
+}
+
+// importPathToNameGoPath finds out the actual package name, as declared in its .go files.
+// If there's a problem, it falls back to using importPathToNameBasic.
+func importPathToNameGoPath(importPath string) (packageName string) {
+	if buildPkg, err := build.Import(importPath, "", 0); err == nil {
+		return buildPkg.Name
+	} else {
+		return importPathToNameBasic(importPath)
+	}
+}
+
+type pkg struct {
+	importpath string // full pkg import path, e.g. "net/http"
+	dir        string // absolute file path to pkg directory e.g. "/usr/lib/go/src/fmt"
+}
+
+var pkgIndexOnce sync.Once
+
+var pkgIndex struct {
+	sync.Mutex
+	m map[string][]pkg // shortname => []pkg, e.g "http" => "net/http"
+}
+
+// gate is a semaphore for limiting concurrency.
+type gate chan struct{}
+
+func (g gate) enter() { g <- struct{}{} }
+func (g gate) leave() { <-g }
+
+// fsgate protects the OS & filesystem from too much concurrency.
+// Too much disk I/O -> too many threads -> swapping and bad scheduling.
+var fsgate = make(gate, 8)
+
+func loadPkgIndex() {
+	pkgIndex.Lock()
+	pkgIndex.m = make(map[string][]pkg)
+	pkgIndex.Unlock()
+
+	var wg sync.WaitGroup
+	for _, path := range build.Default.SrcDirs() {
+		fsgate.enter()
+		f, err := os.Open(path)
+		if err != nil {
+			fsgate.leave()
+			fmt.Fprint(os.Stderr, err)
+			continue
+		}
+		children, err := f.Readdir(-1)
+		f.Close()
+		fsgate.leave()
+		if err != nil {
+			fmt.Fprint(os.Stderr, err)
+			continue
+		}
+		for _, child := range children {
+			if child.IsDir() {
+				wg.Add(1)
+				go func(path, name string) {
+					defer wg.Done()
+					loadPkg(&wg, path, name)
+				}(path, child.Name())
+			}
+		}
+	}
+	wg.Wait()
+}
+
+func loadPkg(wg *sync.WaitGroup, root, pkgrelpath string) {
+	importpath := filepath.ToSlash(pkgrelpath)
+	dir := filepath.Join(root, importpath)
+
+	fsgate.enter()
+	defer fsgate.leave()
+	pkgDir, err := os.Open(dir)
+	if err != nil {
+		return
+	}
+	children, err := pkgDir.Readdir(-1)
+	pkgDir.Close()
+	if err != nil {
+		return
+	}
+	// hasGo tracks whether a directory actually appears to be a
+	// Go source code directory. If $GOPATH == $HOME, and
+	// $HOME/src has lots of other large non-Go projects in it,
+	// then the calls to importPathToName below can be expensive.
+	hasGo := false
+	for _, child := range children {
+		// Avoid .foo, _foo, and testdata directory trees.
+		name := child.Name()
+		if name == "" || name[0] == '.' || name[0] == '_' || name == "testdata" {
+			continue
+		}
+		if strings.HasSuffix(name, ".go") {
+			hasGo = true
+		}
+		if child.IsDir() {
+			wg.Add(1)
+			go func(root, name string) {
+				defer wg.Done()
+				loadPkg(wg, root, name)
+			}(root, filepath.Join(importpath, name))
+		}
+	}
+	if hasGo {
+		shortName := importPathToName(importpath)
+		pkgIndex.Lock()
+		pkgIndex.m[shortName] = append(pkgIndex.m[shortName], pkg{
+			importpath: importpath,
+			dir:        dir,
+		})
+		pkgIndex.Unlock()
+	}
+
+}
+
+// loadExports returns a list exports for a package.
+var loadExports = loadExportsGoPath
+
+func loadExportsGoPath(dir string) map[string]bool {
+	exports := make(map[string]bool)
+	buildPkg, err := build.ImportDir(dir, 0)
+	if err != nil {
+		if strings.Contains(err.Error(), "no buildable Go source files in") {
+			return nil
+		}
+		fmt.Fprintf(os.Stderr, "could not import %q: %v\n", dir, err)
+		return nil
+	}
+	fset := token.NewFileSet()
+	for _, files := range [...][]string{buildPkg.GoFiles, buildPkg.CgoFiles} {
+		for _, file := range files {
+			f, err := parser.ParseFile(fset, filepath.Join(dir, file), nil, 0)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "could not parse %q: %v\n", file, err)
+				continue
+			}
+			for name := range f.Scope.Objects {
+				if ast.IsExported(name) {
+					exports[name] = true
+				}
+			}
+		}
+	}
+	return exports
+}
+
+// findImport searches for a package with the given symbols.
+// If no package is found, findImport returns "".
+// Declared as a variable rather than a function so goimports can be easily
+// extended by adding a file with an init function.
+var findImport = findImportGoPath
+
+func findImportGoPath(pkgName string, symbols map[string]bool) (string, bool, error) {
+	// Fast path for the standard library.
+	// In the common case we hopefully never have to scan the GOPATH, which can
+	// be slow with moving disks.
+	if pkg, rename, ok := findImportStdlib(pkgName, symbols); ok {
+		return pkg, rename, nil
+	}
+
+	// TODO(sameer): look at the import lines for other Go files in the
+	// local directory, since the user is likely to import the same packages
+	// in the current Go file.  Return rename=true when the other Go files
+	// use a renamed package that's also used in the current file.
+
+	pkgIndexOnce.Do(loadPkgIndex)
+
+	// Collect exports for packages with matching names.
+	var wg sync.WaitGroup
+	var pkgsMu sync.Mutex // guards pkgs
+	// full importpath => exported symbol => True
+	// e.g. "net/http" => "Client" => True
+	pkgs := make(map[string]map[string]bool)
+	pkgIndex.Lock()
+	for _, pkg := range pkgIndex.m[pkgName] {
+		wg.Add(1)
+		go func(importpath, dir string) {
+			defer wg.Done()
+			exports := loadExports(dir)
+			if exports != nil {
+				pkgsMu.Lock()
+				pkgs[importpath] = exports
+				pkgsMu.Unlock()
+			}
+		}(pkg.importpath, pkg.dir)
+	}
+	pkgIndex.Unlock()
+	wg.Wait()
+
+	// Filter out packages missing required exported symbols.
+	for symbol := range symbols {
+		for importpath, exports := range pkgs {
+			if !exports[symbol] {
+				delete(pkgs, importpath)
+			}
+		}
+	}
+	if len(pkgs) == 0 {
+		return "", false, nil
+	}
+
+	// If there are multiple candidate packages, the shortest one wins.
+	// This is a heuristic to prefer the standard library (e.g. "bytes")
+	// over e.g. "github.com/foo/bar/bytes".
+	shortest := ""
+	for importPath := range pkgs {
+		if shortest == "" || len(importPath) < len(shortest) {
+			shortest = importPath
+		}
+	}
+	return shortest, false, nil
+}
+
+type visitFn func(node ast.Node) ast.Visitor
+
+func (fn visitFn) Visit(node ast.Node) ast.Visitor {
+	return fn(node)
+}
+
+func findImportStdlib(shortPkg string, symbols map[string]bool) (importPath string, rename, ok bool) {
+	for symbol := range symbols {
+		path := stdlib[shortPkg+"."+symbol]
+		if path == "" {
+			return "", false, false
+		}
+		if importPath != "" && importPath != path {
+			// Ambiguous. Symbols pointed to different things.
+			return "", false, false
+		}
+		importPath = path
+	}
+	return importPath, false, importPath != ""
+}