go.tools/imports: move goimports from github to go.tools.

From revision d0880223588919729793727c9d65f202a73cda77.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/35850048

cmd/goimports/README

@@ -0,0 +1,30 @@
+This tool updates your Go import lines, adding missing ones and
+removing unreferenced ones.
+
+     $ go get code.google.com/p/go.tools/cmd/goimports
+
+It's a fork of gofmt, and will also format your code, so it can be
+used as a replacement for your gofmt-on-save hook in your editor of
+choice.
+
+For emacs, make sure you have the latest (Go 1.2) go-mode.el:
+   https://go.googlecode.com/hg/misc/emacs/go-mode.el
+
+Then in your .emacs file:
+   (setq gofmt-command "goimports")
+   (add-to-list 'load-path "/home/you/goroot/misc/emacs/")
+   (require 'go-mode-load)
+   (add-hook 'before-save-hook 'gofmt-before-save)
+
+For vim, set "gofmt_command" to "goimports":
+
+    https://code.google.com/p/go/source/detail?r=39c724dd7f252
+    https://code.google.com/p/go/source/browse#hg%2Fmisc%2Fvim
+    etc
+
+For GoSublime, follow the steps described here:
+    http://mdwhatcott.wordpress.com/2013/12/15/installing-and-enabling-goimports-with-gosublime/
+
+For other editors, you probably know what to do.
+
+Happy hacking!

cmd/goimports/goimports.go

@@ -0,0 +1,193 @@
+// 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 main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/scanner"
+	"io"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	"code.google.com/p/go.tools/imports"
+)
+
+var (
+	// main operation modes
+	list   = flag.Bool("l", false, "list files whose formatting differs from goimport's")
+	write  = flag.Bool("w", false, "write result to (source) file instead of stdout")
+	doDiff = flag.Bool("d", false, "display diffs instead of rewriting files")
+
+	options  = &imports.Options{}
+	exitCode = 0
+)
+
+func init() {
+	flag.BoolVar(&options.AllErrors, "e", false, "report all errors (not just the first 10 on different lines)")
+	flag.BoolVar(&options.Comments, "comments", true, "print comments")
+	flag.IntVar(&options.TabWidth, "tabwidth", 8, "tab width")
+	flag.BoolVar(&options.TabIndent, "tabs", true, "indent with tabs")
+}
+
+func report(err error) {
+	scanner.PrintError(os.Stderr, err)
+	exitCode = 2
+}
+
+func usage() {
+	fmt.Fprintf(os.Stderr, "usage: goimports [flags] [path ...]\n")
+	flag.PrintDefaults()
+	os.Exit(2)
+}
+
+func isGoFile(f os.FileInfo) bool {
+	// ignore non-Go files
+	name := f.Name()
+	return !f.IsDir() && !strings.HasPrefix(name, ".") && strings.HasSuffix(name, ".go")
+}
+
+func processFile(filename string, in io.Reader, out io.Writer, stdin bool) error {
+	opt := options
+	if stdin {
+		nopt := *options
+		nopt.Fragment = true
+		opt = &nopt
+	}
+
+	if in == nil {
+		f, err := os.Open(filename)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		in = f
+	}
+
+	src, err := ioutil.ReadAll(in)
+	if err != nil {
+		return err
+	}
+
+	res, err := imports.Process(filename, src, opt)
+	if err != nil {
+		return err
+	}
+
+	if !bytes.Equal(src, res) {
+		// formatting has changed
+		if *list {
+			fmt.Fprintln(out, filename)
+		}
+		if *write {
+			err = ioutil.WriteFile(filename, res, 0)
+			if err != nil {
+				return err
+			}
+		}
+		if *doDiff {
+			data, err := diff(src, res)
+			if err != nil {
+				return fmt.Errorf("computing diff: %s", err)
+			}
+			fmt.Printf("diff %s gofmt/%s\n", filename, filename)
+			out.Write(data)
+		}
+	}
+
+	if !*list && !*write && !*doDiff {
+		_, err = out.Write(res)
+	}
+
+	return err
+}
+
+func visitFile(path string, f os.FileInfo, err error) error {
+	if err == nil && isGoFile(f) {
+		err = processFile(path, nil, os.Stdout, false)
+	}
+	if err != nil {
+		report(err)
+	}
+	return nil
+}
+
+func walkDir(path string) {
+	filepath.Walk(path, visitFile)
+}
+
+func main() {
+	runtime.GOMAXPROCS(runtime.NumCPU())
+
+	// call gofmtMain in a separate function
+	// so that it can use defer and have them
+	// run before the exit.
+	gofmtMain()
+	os.Exit(exitCode)
+}
+
+func gofmtMain() {
+	flag.Usage = usage
+	flag.Parse()
+
+	if options.TabWidth < 0 {
+		fmt.Fprintf(os.Stderr, "negative tabwidth %d\n", options.TabWidth)
+		exitCode = 2
+		return
+	}
+
+	if flag.NArg() == 0 {
+		if err := processFile("<standard input>", os.Stdin, os.Stdout, true); err != nil {
+			report(err)
+		}
+		return
+	}
+
+	for i := 0; i < flag.NArg(); i++ {
+		path := flag.Arg(i)
+		switch dir, err := os.Stat(path); {
+		case err != nil:
+			report(err)
+		case dir.IsDir():
+			walkDir(path)
+		default:
+			if err := processFile(path, nil, os.Stdout, false); err != nil {
+				report(err)
+			}
+		}
+	}
+}
+
+func diff(b1, b2 []byte) (data []byte, err error) {
+	f1, err := ioutil.TempFile("", "gofmt")
+	if err != nil {
+		return
+	}
+	defer os.Remove(f1.Name())
+	defer f1.Close()
+
+	f2, err := ioutil.TempFile("", "gofmt")
+	if err != nil {
+		return
+	}
+	defer os.Remove(f2.Name())
+	defer f2.Close()
+
+	f1.Write(b1)
+	f2.Write(b2)
+
+	data, err = exec.Command("diff", "-u", f1.Name(), f2.Name()).CombinedOutput()
+	if len(data) > 0 {
+		// diff exits with a non-zero status when the files don't match.
+		// Ignore that failure as long as we get output.
+		err = nil
+	}
+	return
+}

imports/fix.go

@@ -0,0 +1,328 @@
+// 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"
+
+	"code.google.com/p/go.tools/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(f *ast.File) (added []string, err error) {
+	// refs are a set of possible package references currently unsatisified 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)
+
+	// Search for imports matching potential package references.
+	searches := 0
+	type result struct {
+		ipath 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, err := findImport(pkgName, symbols)
+			results <- result{ipath, err}
+		}(pkgName, symbols)
+		searches++
+	}
+	for i := 0; i < searches; i++ {
+		result := <-results
+		if result.err != nil {
+			return nil, result.err
+		}
+		if result.ipath != "" {
+			astutil.AddImport(fset, f, result.ipath)
+			added = append(added, result.ipath)
+		}
+	}
+
+	// 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)
+	}
+
+	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"
+}
+
+func loadPkgIndex() {
+	pkgIndex.Lock()
+	pkgIndex.m = make(map[string][]pkg)
+	pkgIndex.Unlock()
+
+	var wg sync.WaitGroup
+	for _, path := range build.Default.SrcDirs() {
+		f, err := os.Open(path)
+		if err != nil {
+			fmt.Fprint(os.Stderr, err)
+			continue
+		}
+		children, err := f.Readdir(-1)
+		f.Close()
+		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()
+}
+
+var fset = token.NewFileSet()
+
+func loadPkg(wg *sync.WaitGroup, root, pkgrelpath string) {
+	importpath := filepath.ToSlash(pkgrelpath)
+	shortName := importPathToName(importpath)
+
+	dir := filepath.Join(root, importpath)
+	pkgIndex.Lock()
+	pkgIndex.m[shortName] = append(pkgIndex.m[shortName], pkg{
+		importpath: importpath,
+		dir:        dir,
+	})
+	pkgIndex.Unlock()
+
+	pkgDir, err := os.Open(dir)
+	if err != nil {
+		return
+	}
+	children, err := pkgDir.Readdir(-1)
+	pkgDir.Close()
+	if err != nil {
+		return
+	}
+	for _, child := range children {
+		name := child.Name()
+		if name == "" {
+			continue
+		}
+		if c := name[0]; c == '.' || ('0' <= c && c <= '9') {
+			continue
+		}
+		if child.IsDir() {
+			wg.Add(1)
+			go func(root, name string) {
+				defer wg.Done()
+				loadPkg(wg, root, name)
+			}(root, filepath.Join(importpath, name))
+		}
+	}
+}
+
+// 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", dir, err)
+		return nil
+	}
+	for _, file := range buildPkg.GoFiles {
+		f, err := parser.ParseFile(fset, filepath.Join(dir, file), nil, 0)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "could not parse %q: %v", 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, error) {
+
+	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 "", 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, nil
+}
+
+type visitFn func(node ast.Node) ast.Visitor
+
+func (fn visitFn) Visit(node ast.Node) ast.Visitor {
+	return fn(node)
+}

imports/fix_test.go

@@ -0,0 +1,531 @@
+// 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 (
+	"bytes"
+	"flag"
+	"go/build"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+var only = flag.String("only", "", "If non-empty, the fix test to run")
+
+var tests = []struct {
+	name    string
+	in, out string
+}{
+	// Adding an import to an existing parenthesized import
+	{
+		name: "factored_imports_add",
+		in: `package foo
+import (
+  "fmt"
+)
+func bar() {
+var b bytes.Buffer
+fmt.Println(b.String())
+}
+`,
+		out: `package foo
+
+import (
+	"bytes"
+	"fmt"
+)
+
+func bar() {
+	var b bytes.Buffer
+	fmt.Println(b.String())
+}
+`,
+	},
+
+	// Adding an import to an existing parenthesized import,
+	// verifying it goes into the first section.
+	{
+		name: "factored_imports_add_first_sec",
+		in: `package foo
+import (
+  "fmt"
+
+  "appengine"
+)
+func bar() {
+var b bytes.Buffer
+_ = appengine.IsDevServer
+fmt.Println(b.String())
+}
+`,
+		out: `package foo
+
+import (
+	"bytes"
+	"fmt"
+
+	"appengine"
+)
+
+func bar() {
+	var b bytes.Buffer
+	_ = appengine.IsDevServer
+	fmt.Println(b.String())
+}
+`,
+	},
+
+	// Adding an import to an existing parenthesized import,
+	// verifying it goes into the first section. (test 2)
+	{
+		name: "factored_imports_add_first_sec_2",
+		in: `package foo
+import (
+  "fmt"
+
+  "appengine"
+)
+func bar() {
+_ = math.NaN
+_ = fmt.Sprintf
+_ = appengine.IsDevServer
+}
+`,
+		out: `package foo
+
+import (
+	"fmt"
+	"math"
+
+	"appengine"
+)
+
+func bar() {
+	_ = math.NaN
+	_ = fmt.Sprintf
+	_ = appengine.IsDevServer
+}
+`,
+	},
+
+	// Adding a new import line, without parens
+	{
+		name: "add_import_section",
+		in: `package foo
+func bar() {
+var b bytes.Buffer
+}
+`,
+		out: `package foo
+
+import "bytes"
+
+func bar() {
+	var b bytes.Buffer
+}
+`,
+	},
+
+	// Adding two new imports, which should make a parenthesized import decl.
+	{
+		name: "add_import_paren_section",
+		in: `package foo
+func bar() {
+_, _ := bytes.Buffer, zip.NewReader
+}
+`,
+		out: `package foo
+
+import (
+	"archive/zip"
+	"bytes"
+)
+
+func bar() {
+	_, _ := bytes.Buffer, zip.NewReader
+}
+`,
+	},
+
+	// Make sure we don't add things twice
+	{
+		name: "no_double_add",
+		in: `package foo
+func bar() {
+_, _ := bytes.Buffer, bytes.NewReader
+}
+`,
+		out: `package foo
+
+import "bytes"
+
+func bar() {
+	_, _ := bytes.Buffer, bytes.NewReader
+}
+`,
+	},
+
+	// Remove unused imports, 1 of a factored block
+	{
+		name: "remove_unused_1_of_2",
+		in: `package foo
+import (
+"bytes"
+"fmt"
+)
+
+func bar() {
+_, _ := bytes.Buffer, bytes.NewReader
+}
+`,
+		out: `package foo
+
+import "bytes"
+
+func bar() {
+	_, _ := bytes.Buffer, bytes.NewReader
+}
+`,
+	},
+
+	// Remove unused imports, 2 of 2
+	{
+		name: "remove_unused_2_of_2",
+		in: `package foo
+import (
+"bytes"
+"fmt"
+)
+
+func bar() {
+}
+`,
+		out: `package foo
+
+func bar() {
+}
+`,
+	},
+
+	// Remove unused imports, 1 of 1
+	{
+		name: "remove_unused_1_of_1",
+		in: `package foo
+
+import "fmt"
+
+func bar() {
+}
+`,
+		out: `package foo
+
+func bar() {
+}
+`,
+	},
+
+	// Don't remove empty imports.
+	{
+		name: "dont_remove_empty_imports",
+		in: `package foo
+import (
+_ "image/png"
+_ "image/jpeg"
+)
+`,
+		out: `package foo
+
+import (
+	_ "image/jpeg"
+	_ "image/png"
+)
+`,
+	},
+
+	// Don't remove dot imports.
+	{
+		name: "dont_remove_dot_imports",
+		in: `package foo
+import (
+. "foo"
+. "bar"
+)
+`,
+		out: `package foo
+
+import (
+	. "bar"
+	. "foo"
+)
+`,
+	},
+
+	// Skip refs the parser can resolve.
+	{
+		name: "skip_resolved_refs",
+		in: `package foo
+
+func f() {
+	type t struct{ Println func(string) }
+	fmt := t{Println: func(string) {}}
+	fmt.Println("foo")
+}
+`,
+		out: `package foo
+
+func f() {
+	type t struct{ Println func(string) }
+	fmt := t{Println: func(string) {}}
+	fmt.Println("foo")
+}
+`,
+	},
+
+	// Do not add a package we already have a resolution for.
+	{
+		name: "skip_template",
+		in: `package foo
+
+import "html/template"
+
+func f() { t = template.New("sometemplate") }
+`,
+		out: `package foo
+
+import "html/template"
+
+func f() { t = template.New("sometemplate") }
+`,
+	},
+
+	// Don't touch cgo
+	{
+		name: "cgo",
+		in: `package foo
+
+/*
+#include <foo.h>
+*/
+import "C"
+`,
+		out: `package foo
+
+/*
+#include <foo.h>
+*/
+import "C"
+`,
+	},
+
+	// Put some things in their own section
+	{
+		name: "make_sections",
+		in: `package foo
+
+import (
+"os"
+)
+
+func foo () {
+_, _ = os.Args, fmt.Println
+_, _ = appengine.FooSomething, user.Current
+}
+`,
+		out: `package foo
+
+import (
+	"fmt"
+	"os"
+
+	"appengine"
+	"appengine/user"
+)
+
+func foo() {
+	_, _ = os.Args, fmt.Println
+	_, _ = appengine.FooSomething, user.Current
+}
+`,
+	},
+
+	// Delete existing empty import block
+	{
+		name: "delete_empty_import_block",
+		in: `package foo
+
+import ()
+`,
+		out: `package foo
+`,
+	},
+
+	// Use existing empty import block
+	{
+		name: "use_empty_import_block",
+		in: `package foo
+
+import ()
+
+func f() {
+	_ = fmt.Println
+}
+`,
+		out: `package foo
+
+import "fmt"
+
+func f() {
+	_ = fmt.Println
+}
+`,
+	},
+
+	// Blank line before adding new section.
+	{
+		name: "blank_line_before_new_group",
+		in: `package foo
+
+import (
+	"fmt"
+	"net"
+)
+
+func f() {
+	_ = net.Dial
+	_ = fmt.Printf
+	_ = snappy.Foo
+}
+`,
+		out: `package foo
+
+import (
+	"fmt"
+	"net"
+
+	"code.google.com/p/snappy-go/snappy"
+)
+
+func f() {
+	_ = net.Dial
+	_ = fmt.Printf
+	_ = snappy.Foo
+}
+`,
+	},
+
+	// Blank line between standard library and third-party stuff.
+	{
+		name: "blank_line_separating_std_and_third_party",
+		in: `package foo
+
+import (
+	"code.google.com/p/snappy-go/snappy"
+	"fmt"
+	"net"
+)
+
+func f() {
+	_ = net.Dial
+	_ = fmt.Printf
+	_ = snappy.Foo
+}
+`,
+		out: `package foo
+
+import (
+	"fmt"
+	"net"
+
+	"code.google.com/p/snappy-go/snappy"
+)
+
+func f() {
+	_ = net.Dial
+	_ = fmt.Printf
+	_ = snappy.Foo
+}
+`,
+	},
+}
+
+func TestFixImports(t *testing.T) {
+	simplePkgs := map[string]string{
+		"fmt":       "fmt",
+		"os":        "os",
+		"math":      "math",
+		"appengine": "appengine",
+		"user":      "appengine/user",
+		"zip":       "archive/zip",
+		"bytes":     "bytes",
+		"snappy":    "code.google.com/p/snappy-go/snappy",
+	}
+	findImport = func(pkgName string, symbols map[string]bool) (string, error) {
+		return simplePkgs[pkgName], nil
+	}
+
+	for _, tt := range tests {
+		if *only != "" && tt.name != *only {
+			continue
+		}
+		var buf bytes.Buffer
+		err := processFile("foo.go", strings.NewReader(tt.in), &buf, false)
+		if err != nil {
+			t.Errorf("error on %q: %v", tt.name, err)
+			continue
+		}
+		if got := buf.String(); got != tt.out {
+			t.Errorf("results diff on %q\nGOT:\n%s\nWANT:\n%s\n", tt.name, got, tt.out)
+		}
+	}
+}
+
+func TestFindImportGoPath(t *testing.T) {
+	goroot, err := ioutil.TempDir("", "goimports-")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(goroot)
+	// Test against imaginary bits/bytes package in std lib
+	bytesDir := filepath.Join(goroot, "src", "pkg", "bits", "bytes")
+	if err := os.MkdirAll(bytesDir, 0755); err != nil {
+		t.Fatal(err)
+	}
+	bytesSrcPath := filepath.Join(bytesDir, "bytes.go")
+	bytesPkgPath := "bits/bytes"
+	bytesSrc := []byte(`package bytes
+
+type Buffer2 struct {}
+`)
+	if err := ioutil.WriteFile(bytesSrcPath, bytesSrc, 0775); err != nil {
+		t.Fatal(err)
+	}
+	oldGOROOT := build.Default.GOROOT
+	oldGOPATH := build.Default.GOPATH
+	build.Default.GOROOT = goroot
+	build.Default.GOPATH = ""
+	defer func() {
+		build.Default.GOROOT = oldGOROOT
+		build.Default.GOPATH = oldGOPATH
+	}()
+
+	got, err := findImportGoPath("bytes", map[string]bool{"Buffer2": true})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != bytesPkgPath {
+		t.Errorf(`findImportGoPath("bytes", Buffer2 ...)=%q, want "%s"`, got, bytesPkgPath)
+	}
+
+	got, err = findImportGoPath("bytes", map[string]bool{"Missing": true})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != "" {
+		t.Errorf(`findImportGoPath("bytes", Missing ...)=%q, want ""`, got)
+	}
+}

imports/imports.go

@@ -0,0 +1,240 @@
+// 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 implements a Go pretty-printer (like package "go/format")
+// that also adds or removes import statements as necessary.
+package imports
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/printer"
+	"go/token"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"code.google.com/p/go.tools/astutil"
+)
+
+// Options specifies options for processing files.
+type Options struct {
+	Fragment  bool // Accept fragement of a source file (no package statement)
+	AllErrors bool // Report all errors (not just the first 10 on different lines)
+
+	Comments  bool // Print comments (true if nil *Options provided)
+	TabIndent bool // Use tabs for indent (true if nil *Options provided)
+	TabWidth  int  // Tab width (8 if nil *Options provided)
+}
+
+// Process formats and adjusts imports for the provided file.
+// If opt is nil the defaults are used.
+func Process(filename string, src []byte, opt *Options) ([]byte, error) {
+	if opt == nil {
+		opt = &Options{Comments: true, TabIndent: true, TabWidth: 8}
+	}
+
+	fileSet := token.NewFileSet()
+	file, adjust, err := parse(fileSet, filename, src, opt)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = fixImports(file)
+	if err != nil {
+		return nil, err
+	}
+
+	sortImports(fileSet, file)
+	imps := astutil.Imports(fileSet, file)
+
+	var spacesBefore []string // import paths we need spaces before
+	if len(imps) == 1 {
+		// We have just one block of imports. See if any are in different groups numbers.
+		lastGroup := -1
+		for _, importSpec := range imps[0] {
+			importPath, _ := strconv.Unquote(importSpec.Path.Value)
+			groupNum := importGroup(importPath)
+			if groupNum != lastGroup && lastGroup != -1 {
+				spacesBefore = append(spacesBefore, importPath)
+			}
+			lastGroup = groupNum
+		}
+
+	}
+
+	printerMode := printer.UseSpaces
+	if opt.TabIndent {
+		printerMode |= printer.TabIndent
+	}
+	printConfig := &printer.Config{Mode: printerMode, Tabwidth: opt.TabWidth}
+
+	var buf bytes.Buffer
+	err = printConfig.Fprint(&buf, fileSet, file)
+	if err != nil {
+		return nil, err
+	}
+	out := buf.Bytes()
+	if adjust != nil {
+		out = adjust(src, out)
+	}
+	if len(spacesBefore) > 0 {
+		out = addImportSpaces(bytes.NewReader(out), spacesBefore)
+	}
+	return out, nil
+}
+
+// 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)
+	if opt.Comments {
+		parserMode |= parser.ParseComments
+	}
+	if opt.AllErrors {
+		parserMode |= parser.AllErrors
+	}
+
+	// Try as whole source file.
+	file, err := parser.ParseFile(fset, filename, src, parserMode)
+	if err == nil {
+		return file, nil, nil
+	}
+	// If the error is that the source file didn't begin with a
+	// package line and we accept fragmented input, fall through to
+	// try as a source fragment.  Stop and return on any other error.
+	if !opt.Fragment || !strings.Contains(err.Error(), "expected 'package'") {
+		return nil, nil, err
+	}
+
+	// If this is a declaration list, make it a source file
+	// by inserting a package clause.
+	// Insert using a ;, not a newline, so that the line numbers
+	// in psrc match the ones in src.
+	psrc := append([]byte("package p;"), src...)
+	file, err = parser.ParseFile(fset, filename, psrc, parserMode)
+	if err == nil {
+		adjust := func(orig, src []byte) []byte {
+			// Remove the package clause.
+			// Gofmt has turned the ; into a \n.
+			src = src[len("package p\n"):]
+			return matchSpace(orig, src)
+		}
+		return file, adjust, nil
+	}
+	// If the error is that the source file didn't begin with a
+	// declaration, fall through to try as a statement list.
+	// Stop and return on any other error.
+	if !strings.Contains(err.Error(), "expected declaration") {
+		return nil, nil, err
+	}
+
+	// If this is a statement list, make it a source file
+	// by inserting a package clause and turning the list
+	// into a function body.  This handles expressions too.
+	// Insert using a ;, not a newline, so that the line numbers
+	// in fsrc match the ones in src.
+	fsrc := append(append([]byte("package p; func _() {"), src...), '}')
+	file, err = parser.ParseFile(fset, filename, fsrc, parserMode)
+	if err == nil {
+		adjust := func(orig, src []byte) []byte {
+			// Remove the wrapping.
+			// Gofmt has turned the ; into a \n\n.
+			src = src[len("package p\n\nfunc _() {"):]
+			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)
+			return matchSpace(orig, src)
+		}
+		return file, adjust, nil
+	}
+
+	// Failed, and out of options.
+	return nil, nil, err
+}
+
+func cutSpace(b []byte) (before, middle, after []byte) {
+	i := 0
+	for i < len(b) && (b[i] == ' ' || b[i] == '\t' || b[i] == '\n') {
+		i++
+	}
+	j := len(b)
+	for j > 0 && (b[j-1] == ' ' || b[j-1] == '\t' || b[j-1] == '\n') {
+		j--
+	}
+	if i <= j {
+		return b[:i], b[i:j], b[j:]
+	}
+	return nil, nil, b[j:]
+}
+
+// matchSpace reformats src to use the same space context as orig.
+// 1) If orig begins with blank lines, matchSpace inserts them at the beginning of src.
+// 2) matchSpace copies the indentation of the first non-blank line in orig
+//    to every non-blank line in src.
+// 3) matchSpace copies the trailing space from orig and uses it in place
+//   of src's trailing space.
+func matchSpace(orig []byte, src []byte) []byte {
+	before, _, after := cutSpace(orig)
+	i := bytes.LastIndex(before, []byte{'\n'})
+	before, indent := before[:i+1], before[i+1:]
+
+	_, src, _ = cutSpace(src)
+
+	var b bytes.Buffer
+	b.Write(before)
+	for len(src) > 0 {
+		line := src
+		if i := bytes.IndexByte(line, '\n'); i >= 0 {
+			line, src = line[:i+1], line[i+1:]
+		} else {
+			src = nil
+		}
+		if len(line) > 0 && line[0] != '\n' { // not blank
+			b.Write(indent)
+		}
+		b.Write(line)
+	}
+	b.Write(after)
+	return b.Bytes()
+}
+
+var impLine = regexp.MustCompile(`^\s+(?:\w+\s+)?"(.+)"`)
+
+func addImportSpaces(r io.Reader, breaks []string) []byte {
+	var out bytes.Buffer
+	sc := bufio.NewScanner(r)
+	inImports := false
+	done := false
+	for sc.Scan() {
+		s := sc.Text()
+
+		if !inImports && !done && strings.HasPrefix(s, "import") {
+			inImports = true
+		}
+		if inImports && (strings.HasPrefix(s, "var") ||
+			strings.HasPrefix(s, "func") ||
+			strings.HasPrefix(s, "const") ||
+			strings.HasPrefix(s, "type")) {
+			done = true
+			inImports = false
+		}
+		if inImports && len(breaks) > 0 {
+			if m := impLine.FindStringSubmatch(s); m != nil {
+				if m[1] == string(breaks[0]) {
+					out.WriteByte('\n')
+					breaks = breaks[1:]
+				}
+			}
+		}
+
+		fmt.Fprintln(&out, s)
+	}
+	return out.Bytes()
+}

imports/mkindex.go

@@ -0,0 +1,173 @@
+// +build ignore
+
+// 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.
+
+// Command mkindex creates the file "pkgindex.go" containing an index of the Go
+// standard library. The file is intended to be built as part of the imports
+// package, so that the package may be used in environments where a GOROOT is
+// not available (such as App Engine).
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+var (
+	pkgIndex = make(map[string][]pkg)
+	exports  = make(map[string]map[string]bool)
+)
+
+func main() {
+	// Don't use GOPATH.
+	ctx := build.Default
+	ctx.GOPATH = ""
+
+	// Populate pkgIndex global from GOROOT.
+	for _, path := range ctx.SrcDirs() {
+		f, err := os.Open(path)
+		if err != nil {
+			log.Print(err)
+			continue
+		}
+		children, err := f.Readdir(-1)
+		f.Close()
+		if err != nil {
+			log.Print(err)
+			continue
+		}
+		for _, child := range children {
+			if child.IsDir() {
+				loadPkg(path, child.Name())
+			}
+		}
+	}
+	// Populate exports global.
+	for _, ps := range pkgIndex {
+		for _, p := range ps {
+			e := loadExports(p.dir)
+			if e != nil {
+				exports[p.dir] = e
+			}
+		}
+	}
+
+	// Construct source file.
+	var buf bytes.Buffer
+	fmt.Fprint(&buf, pkgIndexHead)
+	fmt.Fprintf(&buf, "var pkgIndexMaster = %#v\n", pkgIndex)
+	fmt.Fprintf(&buf, "var exportsMaster = %#v\n", exports)
+	src := buf.Bytes()
+
+	// Replace main.pkg type name with pkg.
+	src = bytes.Replace(src, []byte("main.pkg"), []byte("pkg"), -1)
+	// Replace actual GOROOT with "/go".
+	src = bytes.Replace(src, []byte(ctx.GOROOT), []byte("/go"), -1)
+	// Add some line wrapping.
+	src = bytes.Replace(src, []byte("}, "), []byte("},\n"), -1)
+	src = bytes.Replace(src, []byte("true, "), []byte("true,\n"), -1)
+
+	var err error
+	src, err = format.Source(src)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Write out source file.
+	err = ioutil.WriteFile("pkgindex.go", src, 0644)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+const pkgIndexHead = `package imports
+
+func init() {
+	pkgIndexOnce.Do(func() {
+		pkgIndex.m = pkgIndexMaster
+	})
+	loadExports = func(dir string) map[string]bool {
+		return exportsMaster[dir]
+	}
+}
+`
+
+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 fset = token.NewFileSet()
+
+func loadPkg(root, importpath string) {
+	shortName := path.Base(importpath)
+	if shortName == "testdata" {
+		return
+	}
+
+	dir := filepath.Join(root, importpath)
+	pkgIndex[shortName] = append(pkgIndex[shortName], pkg{
+		importpath: importpath,
+		dir:        dir,
+	})
+
+	pkgDir, err := os.Open(dir)
+	if err != nil {
+		return
+	}
+	children, err := pkgDir.Readdir(-1)
+	pkgDir.Close()
+	if err != nil {
+		return
+	}
+	for _, child := range children {
+		name := child.Name()
+		if name == "" {
+			continue
+		}
+		if c := name[0]; c == '.' || ('0' <= c && c <= '9') {
+			continue
+		}
+		if child.IsDir() {
+			loadPkg(root, filepath.Join(importpath, name))
+		}
+	}
+}
+
+func loadExports(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
+		}
+		log.Printf("could not import %q: %v", dir, err)
+		return nil
+	}
+	for _, file := range buildPkg.GoFiles {
+		f, err := parser.ParseFile(fset, filepath.Join(dir, file), nil, 0)
+		if err != nil {
+			log.Printf("could not parse %q: %v", file, err)
+			continue
+		}
+		for name := range f.Scope.Objects {
+			if ast.IsExported(name) {
+				exports[name] = true
+			}
+		}
+	}
+	return exports
+}

imports/sortimports.go

@@ -0,0 +1,214 @@
+// +build go1.2
+
+// 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.
+
+// Hacked up copy of go/ast/import.go
+
+package imports
+
+import (
+	"go/ast"
+	"go/token"
+	"sort"
+	"strconv"
+)
+
+// 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.
+func sortImports(fset *token.FileSet, f *ast.File) {
+	for i, d := range f.Decls {
+		d, ok := d.(*ast.GenDecl)
+		if !ok || d.Tok != token.IMPORT {
+			// Not an import declaration, so we're done.
+			// Imports are always first.
+			break
+		}
+
+		if len(d.Specs) == 0 {
+			// Empty import block, remove it.
+			f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
+		}
+
+		if !d.Lparen.IsValid() {
+			// Not a block: sorted by default.
+			continue
+		}
+
+		// Identify and sort runs of specs on successive lines.
+		i := 0
+		specs := d.Specs[:0]
+		for j, s := range d.Specs {
+			if j > i && fset.Position(s.Pos()).Line > 1+fset.Position(d.Specs[j-1].End()).Line {
+				// j begins a new run.  End this one.
+				specs = append(specs, sortSpecs(fset, f, d.Specs[i:j])...)
+				i = j
+			}
+		}
+		specs = append(specs, sortSpecs(fset, f, d.Specs[i:])...)
+		d.Specs = specs
+
+		// Deduping can leave a blank line before the rparen; clean that up.
+		if len(d.Specs) > 0 {
+			lastSpec := d.Specs[len(d.Specs)-1]
+			lastLine := fset.Position(lastSpec.Pos()).Line
+			if rParenLine := fset.Position(d.Rparen).Line; rParenLine > lastLine+1 {
+				fset.File(d.Rparen).MergeLine(rParenLine - 1)
+			}
+		}
+	}
+}
+
+func importPath(s ast.Spec) string {
+	t, err := strconv.Unquote(s.(*ast.ImportSpec).Path.Value)
+	if err == nil {
+		return t
+	}
+	return ""
+}
+
+func importName(s ast.Spec) string {
+	n := s.(*ast.ImportSpec).Name
+	if n == nil {
+		return ""
+	}
+	return n.Name
+}
+
+func importComment(s ast.Spec) string {
+	c := s.(*ast.ImportSpec).Comment
+	if c == nil {
+		return ""
+	}
+	return c.Text()
+}
+
+// collapse indicates whether prev may be removed, leaving only next.
+func collapse(prev, next ast.Spec) bool {
+	if importPath(next) != importPath(prev) || importName(next) != importName(prev) {
+		return false
+	}
+	return prev.(*ast.ImportSpec).Comment == nil
+}
+
+type posSpan struct {
+	Start token.Pos
+	End   token.Pos
+}
+
+func sortSpecs(fset *token.FileSet, f *ast.File, specs []ast.Spec) []ast.Spec {
+	// Can't short-circuit here even if specs are already sorted,
+	// since they might yet need deduplication.
+	// A lone import, however, may be safely ignored.
+	if len(specs) <= 1 {
+		return specs
+	}
+
+	// Record positions for specs.
+	pos := make([]posSpan, len(specs))
+	for i, s := range specs {
+		pos[i] = posSpan{s.Pos(), s.End()}
+	}
+
+	// Identify comments in this range.
+	// Any comment from pos[0].Start to the final line counts.
+	lastLine := fset.Position(pos[len(pos)-1].End).Line
+	cstart := len(f.Comments)
+	cend := len(f.Comments)
+	for i, g := range f.Comments {
+		if g.Pos() < pos[0].Start {
+			continue
+		}
+		if i < cstart {
+			cstart = i
+		}
+		if fset.Position(g.End()).Line > lastLine {
+			cend = i
+			break
+		}
+	}
+	comments := f.Comments[cstart:cend]
+
+	// Assign each comment to the import spec preceding it.
+	importComment := map[*ast.ImportSpec][]*ast.CommentGroup{}
+	specIndex := 0
+	for _, g := range comments {
+		for specIndex+1 < len(specs) && pos[specIndex+1].Start <= g.Pos() {
+			specIndex++
+		}
+		s := specs[specIndex].(*ast.ImportSpec)
+		importComment[s] = append(importComment[s], g)
+	}
+
+	// Sort the import specs by import path.
+	// Remove duplicates, when possible without data loss.
+	// Reassign the import paths to have the same position sequence.
+	// Reassign each comment to abut the end of its spec.
+	// Sort the comments by new position.
+	sort.Sort(byImportSpec(specs))
+
+	// Dedup. Thanks to our sorting, we can just consider
+	// adjacent pairs of imports.
+	deduped := specs[:0]
+	for i, s := range specs {
+		if i == len(specs)-1 || !collapse(s, specs[i+1]) {
+			deduped = append(deduped, s)
+		} else {
+			p := s.Pos()
+			fset.File(p).MergeLine(fset.Position(p).Line)
+		}
+	}
+	specs = deduped
+
+	// Fix up comment positions
+	for i, s := range specs {
+		s := s.(*ast.ImportSpec)
+		if s.Name != nil {
+			s.Name.NamePos = pos[i].Start
+		}
+		s.Path.ValuePos = pos[i].Start
+		s.EndPos = pos[i].End
+		for _, g := range importComment[s] {
+			for _, c := range g.List {
+				c.Slash = pos[i].End
+			}
+		}
+	}
+
+	sort.Sort(byCommentPos(comments))
+
+	return specs
+}
+
+type byImportSpec []ast.Spec // slice of *ast.ImportSpec
+
+func (x byImportSpec) Len() int      { return len(x) }
+func (x byImportSpec) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+func (x byImportSpec) Less(i, j int) bool {
+	ipath := importPath(x[i])
+	jpath := importPath(x[j])
+
+	igroup := importGroup(ipath)
+	jgroup := importGroup(jpath)
+	if igroup != jgroup {
+		return igroup < jgroup
+	}
+
+	if ipath != jpath {
+		return ipath < jpath
+	}
+	iname := importName(x[i])
+	jname := importName(x[j])
+
+	if iname != jname {
+		return iname < jname
+	}
+	return importComment(x[i]) < importComment(x[j])
+}
+
+type byCommentPos []*ast.CommentGroup
+
+func (x byCommentPos) Len() int           { return len(x) }
+func (x byCommentPos) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
+func (x byCommentPos) Less(i, j int) bool { return x[i].Pos() < x[j].Pos() }

imports/sortimports_compat.go

@@ -0,0 +1,14 @@
+// +build !go1.2
+
+// 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 "go/ast"
+
+// Go 1.1 users don't get fancy package grouping.
+// But this is still gofmt-compliant:
+
+var sortImports = ast.SortImports