message/pipeline: copy over files from cmd/gotext Most of the code will be turned into a package. Change-Id: I47609e5afb176e42d3b0b29bfa04cca23ab6867f Reviewed-on: https://go-review.googlesource.com/82235 Run-TryBot: Marcel van Lohuizen <mpvl@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Nigel Tao <nigeltao@golang.org>

diff --git a/message/pipeline/common.go b/message/pipeline/common.go
new file mode 100644
index 0000000..ae87e44
--- /dev/null
+++ b/message/pipeline/common.go

@@ -0,0 +1,48 @@
+// Copyright 2017 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 (
+	"fmt"
+	"go/build"
+	"go/parser"
+
+	"golang.org/x/tools/go/loader"
+)
+
+const (
+	extractFile  = "extracted.gotext.json"
+	outFile      = "out.gotext.json"
+	gotextSuffix = ".gotext.json"
+)
+
+// NOTE: The command line tool already prefixes with "gotext:".
+var (
+	wrap = func(err error, msg string) error {
+		return fmt.Errorf("%s: %v", msg, err)
+	}
+	wrapf = func(err error, msg string, args ...interface{}) error {
+		return wrap(err, fmt.Sprintf(msg, args...))
+	}
+	errorf = fmt.Errorf
+)
+
+func loadPackages(conf *loader.Config, args []string) (*loader.Program, error) {
+	if len(args) == 0 {
+		args = []string{"."}
+	}
+
+	conf.Build = &build.Default
+	conf.ParserMode = parser.ParseComments
+
+	// Use the initial packages from the command line.
+	args, err := conf.FromArgs(args, false)
+	if err != nil {
+		return nil, wrap(err, "loading packages failed")
+	}
+
+	// Load, parse and type-check the whole program.
+	return conf.Load()
+}

diff --git a/message/pipeline/doc.go b/message/pipeline/doc.go
new file mode 100644
index 0000000..2a274f7
--- /dev/null
+++ b/message/pipeline/doc.go

@@ -0,0 +1,53 @@
+// Code generated by go generate. DO NOT EDIT.
+
+// gotext is a tool for managing text in Go source code.
+//
+// Usage:
+//
+// 	gotext command [arguments]
+//
+// The commands are:
+//
+// 	extract     extracts strings to be translated from code
+// 	rewrite     rewrites fmt functions to use a message Printer
+// 	generate    generates code to insert translated messages
+//
+// Use "go help [command]" for more information about a command.
+//
+// Additional help topics:
+//
+//
+// Use "gotext help [topic]" for more information about that topic.
+//
+//
+// Extracts strings to be translated from code
+//
+// Usage:
+//
+// 	go extract <package>*
+//
+//
+//
+//
+// Rewrites fmt functions to use a message Printer
+//
+// Usage:
+//
+// 	go rewrite <package>
+//
+// rewrite is typically done once for a project. It rewrites all usages of
+// fmt to use x/text's message package whenever a message.Printer is in scope.
+// It rewrites Print and Println calls with constant strings to the equivalent
+// using Printf to allow translators to reorder arguments.
+//
+//
+// Generates code to insert translated messages
+//
+// Usage:
+//
+// 	go generate <package>
+//
+//
+//
+//
+package main

diff --git a/message/pipeline/extract.go b/message/pipeline/extract.go
new file mode 100644
index 0000000..561f050
--- /dev/null
+++ b/message/pipeline/extract.go

@@ -0,0 +1,358 @@
+// Copyright 2016 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"
+	"encoding/json"
+	"fmt"
+	"go/ast"
+	"go/constant"
+	"go/format"
+	"go/token"
+	"go/types"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+
+	"golang.org/x/text/internal"
+	fmtparser "golang.org/x/text/internal/format"
+	"golang.org/x/text/language"
+	"golang.org/x/tools/go/loader"
+)
+
+// TODO:
+// - merge information into existing files
+// - handle different file formats (PO, XLIFF)
+// - handle features (gender, plural)
+// - message rewriting
+
+var (
+	srcLang *string
+	lang    *string
+)
+
+func init() {
+	srcLang = cmdExtract.Flag.String("srclang", "en-US", "the source-code language")
+	lang = cmdExtract.Flag.String("lang", "en-US", "comma-separated list of languages to process")
+}
+
+var cmdExtract = &Command{
+	Run:       runExtract,
+	UsageLine: "extract <package>*",
+	Short:     "extracts strings to be translated from code",
+}
+
+func runExtract(cmd *Command, args []string) error {
+	conf := loader.Config{}
+	prog, err := loadPackages(&conf, args)
+	if err != nil {
+		return wrap(err, "")
+	}
+
+	// print returns Go syntax for the specified node.
+	print := func(n ast.Node) string {
+		var buf bytes.Buffer
+		format.Node(&buf, conf.Fset, n)
+		return buf.String()
+	}
+
+	var messages []Message
+
+	for _, info := range prog.AllPackages {
+		for _, f := range info.Files {
+			// Associate comments with nodes.
+			cmap := ast.NewCommentMap(prog.Fset, f, f.Comments)
+			getComment := func(n ast.Node) string {
+				cs := cmap.Filter(n).Comments()
+				if len(cs) > 0 {
+					return strings.TrimSpace(cs[0].Text())
+				}
+				return ""
+			}
+
+			// Find function calls.
+			ast.Inspect(f, func(n ast.Node) bool {
+				call, ok := n.(*ast.CallExpr)
+				if !ok {
+					return true
+				}
+
+				// Skip calls of functions other than
+				// (*message.Printer).{Sp,Fp,P}rintf.
+				sel, ok := call.Fun.(*ast.SelectorExpr)
+				if !ok {
+					return true
+				}
+				meth := info.Selections[sel]
+				if meth == nil || meth.Kind() != types.MethodVal {
+					return true
+				}
+				// TODO: remove cheap hack and check if the type either
+				// implements some interface or is specifically of type
+				// "golang.org/x/text/message".Printer.
+				m, ok := extractFuncs[path.Base(meth.Recv().String())]
+				if !ok {
+					return true
+				}
+
+				fmtType, ok := m[meth.Obj().Name()]
+				if !ok {
+					return true
+				}
+				// argn is the index of the format string.
+				argn := fmtType.arg
+				if argn >= len(call.Args) {
+					return true
+				}
+
+				args := call.Args[fmtType.arg:]
+
+				fmtMsg, ok := msgStr(info, args[0])
+				if !ok {
+					// TODO: identify the type of the format argument. If it
+					// is not a string, multiple keys may be defined.
+					return true
+				}
+				comment := ""
+				key := []string{}
+				if ident, ok := args[0].(*ast.Ident); ok {
+					key = append(key, ident.Name)
+					if v, ok := ident.Obj.Decl.(*ast.ValueSpec); ok && v.Comment != nil {
+						// TODO: get comment above ValueSpec as well
+						comment = v.Comment.Text()
+					}
+				}
+
+				arguments := []argument{}
+				args = args[1:]
+				simArgs := make([]interface{}, len(args))
+				for i, arg := range args {
+					expr := print(arg)
+					val := ""
+					if v := info.Types[arg].Value; v != nil {
+						val = v.ExactString()
+						simArgs[i] = val
+						switch arg.(type) {
+						case *ast.BinaryExpr, *ast.UnaryExpr:
+							expr = val
+						}
+					}
+					arguments = append(arguments, argument{
+						ArgNum:         i + 1,
+						Type:           info.Types[arg].Type.String(),
+						UnderlyingType: info.Types[arg].Type.Underlying().String(),
+						Expr:           expr,
+						Value:          val,
+						Comment:        getComment(arg),
+						Position:       posString(conf, info, arg.Pos()),
+						// TODO report whether it implements
+						// interfaces plural.Interface,
+						// gender.Interface.
+					})
+				}
+				msg := ""
+
+				ph := placeholders{index: map[string]string{}}
+
+				p := fmtparser.Parser{}
+				p.Reset(simArgs)
+				for p.SetFormat(fmtMsg); p.Scan(); {
+					switch p.Status {
+					case fmtparser.StatusText:
+						msg += p.Text()
+					case fmtparser.StatusSubstitution,
+						fmtparser.StatusBadWidthSubstitution,
+						fmtparser.StatusBadPrecSubstitution:
+						arguments[p.ArgNum-1].used = true
+						arg := arguments[p.ArgNum-1]
+						sub := p.Text()
+						if !p.HasIndex {
+							r, sz := utf8.DecodeLastRuneInString(sub)
+							sub = fmt.Sprintf("%s[%d]%c", sub[:len(sub)-sz], p.ArgNum, r)
+						}
+						msg += fmt.Sprintf("{%s}", ph.addArg(&arg, sub))
+					}
+				}
+				key = append(key, msg)
+
+				// Add additional Placeholders that can be used in translations
+				// that are not present in the string.
+				for _, arg := range arguments {
+					if arg.used {
+						continue
+					}
+					ph.addArg(&arg, fmt.Sprintf("%%[%d]v", arg.ArgNum))
+				}
+
+				if c := getComment(call.Args[0]); c != "" {
+					comment = c
+				}
+
+				messages = append(messages, Message{
+					ID:      key,
+					Key:     fmtMsg,
+					Message: Text{Msg: msg},
+					// TODO(fix): this doesn't get the before comment.
+					Comment:      comment,
+					Placeholders: ph.slice,
+					Position:     posString(conf, info, call.Lparen),
+				})
+				return true
+			})
+		}
+	}
+
+	tag, err := language.Parse(*srcLang)
+	if err != nil {
+		return wrap(err, "")
+	}
+	out := Locale{
+		Language: tag,
+		Messages: messages,
+	}
+	data, err := json.MarshalIndent(out, "", "    ")
+	if err != nil {
+		return wrap(err, "")
+	}
+	os.MkdirAll(*dir, 0755)
+	// TODO: this file can probably go if we replace the extract + generate
+	// cycle with a init once and update cycle.
+	file := filepath.Join(*dir, extractFile)
+	if err := ioutil.WriteFile(file, data, 0644); err != nil {
+		return wrapf(err, "could not create file")
+	}
+
+	langs := append(getLangs(), tag)
+	langs = internal.UniqueTags(langs)
+	for _, tag := range langs {
+		// TODO: inject translations from existing files to avoid retranslation.
+		out.Language = tag
+		data, err := json.MarshalIndent(out, "", "    ")
+		if err != nil {
+			return wrap(err, "JSON marshal failed")
+		}
+		file := filepath.Join(*dir, tag.String(), outFile)
+		if err := os.MkdirAll(filepath.Dir(file), 0750); err != nil {
+			return wrap(err, "dir create failed")
+		}
+		if err := ioutil.WriteFile(file, data, 0740); err != nil {
+			return wrap(err, "write failed")
+		}
+	}
+	return nil
+}
+
+func posString(conf loader.Config, info *loader.PackageInfo, pos token.Pos) string {
+	p := conf.Fset.Position(pos)
+	file := fmt.Sprintf("%s:%d:%d", filepath.Base(p.Filename), p.Line, p.Column)
+	return filepath.Join(info.Pkg.Path(), file)
+}
+
+// extractFuncs indicates the types and methods for which to extract strings,
+// and which argument to extract.
+// TODO: use the types in conf.Import("golang.org/x/text/message") to extract
+// the correct instances.
+var extractFuncs = map[string]map[string]extractType{
+	// TODO: Printer -> *golang.org/x/text/message.Printer
+	"message.Printer": {
+		"Printf":  extractType{arg: 0, format: true},
+		"Sprintf": extractType{arg: 0, format: true},
+		"Fprintf": extractType{arg: 1, format: true},
+
+		"Lookup": extractType{arg: 0},
+	},
+}
+
+type extractType struct {
+	// format indicates if the next arg is a formatted string or whether to
+	// concatenate all arguments
+	format bool
+	// arg indicates the position of the argument to extract.
+	arg int
+}
+
+func getID(arg *argument) string {
+	s := getLastComponent(arg.Expr)
+	s = strip(s)
+	s = strings.Replace(s, " ", "", -1)
+	// For small variable names, use user-defined types for more info.
+	if len(s) <= 2 && arg.UnderlyingType != arg.Type {
+		s = getLastComponent(arg.Type)
+	}
+	return strings.Title(s)
+}
+
+// strip is a dirty hack to convert function calls to placeholder IDs.
+func strip(s string) string {
+	s = strings.Map(func(r rune) rune {
+		if unicode.IsSpace(r) || r == '-' {
+			return '_'
+		}
+		if !unicode.In(r, unicode.Letter, unicode.Mark) {
+			return -1
+		}
+		return r
+	}, s)
+	// Strip "Get" from getter functions.
+	if strings.HasPrefix(s, "Get") || strings.HasPrefix(s, "get") {
+		if len(s) > len("get") {
+			r, _ := utf8.DecodeRuneInString(s)
+			if !unicode.In(r, unicode.Ll, unicode.M) { // not lower or mark
+				s = s[len("get"):]
+			}
+		}
+	}
+	return s
+}
+
+type placeholders struct {
+	index map[string]string
+	slice []Placeholder
+}
+
+func (p *placeholders) addArg(arg *argument, sub string) (id string) {
+	id = getID(arg)
+	id1 := id
+	alt, ok := p.index[id1]
+	for i := 1; ok && alt != sub; i++ {
+		id1 = fmt.Sprintf("%s_%d", id, i)
+		alt, ok = p.index[id1]
+	}
+	p.index[id1] = sub
+	p.slice = append(p.slice, Placeholder{
+		ID:             id1,
+		String:         sub,
+		Type:           arg.Type,
+		UnderlyingType: arg.UnderlyingType,
+		ArgNum:         arg.ArgNum,
+		Expr:           arg.Expr,
+		Comment:        arg.Comment,
+	})
+	return id1
+}
+
+func getLastComponent(s string) string {
+	return s[1+strings.LastIndexByte(s, '.'):]
+}
+
+func msgStr(info *loader.PackageInfo, e ast.Expr) (s string, ok bool) {
+	v := info.Types[e].Value
+	if v == nil || v.Kind() != constant.String {
+		return "", false
+	}
+	s = constant.StringVal(v)
+	// Only record strings with letters.
+	for _, r := range s {
+		if unicode.In(r, unicode.L) {
+			return s, true
+		}
+	}
+	return "", false
+}

diff --git a/message/pipeline/generate.go b/message/pipeline/generate.go
new file mode 100644
index 0000000..0293273
--- /dev/null
+++ b/message/pipeline/generate.go

@@ -0,0 +1,322 @@
+// Copyright 2017 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 (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+	"text/template"
+
+	"golang.org/x/text/collate"
+	"golang.org/x/text/feature/plural"
+	"golang.org/x/text/internal"
+	"golang.org/x/text/internal/catmsg"
+	"golang.org/x/text/internal/gen"
+	"golang.org/x/text/language"
+	"golang.org/x/tools/go/loader"
+)
+
+func init() {
+	out = cmdGenerate.Flag.String("out", "", "output file to write to")
+}
+
+var (
+	out *string
+)
+
+var cmdGenerate = &Command{
+	Run:       runGenerate,
+	UsageLine: "generate <package>",
+	Short:     "generates code to insert translated messages",
+}
+
+var transRe = regexp.MustCompile(`messages\.(.*)\.json`)
+
+func runGenerate(cmd *Command, args []string) error {
+	prog, err := loadPackages(&loader.Config{}, args)
+	if err != nil {
+		return wrap(err, "could not load package")
+	}
+
+	pkgs := prog.InitialPackages()
+	if len(pkgs) != 1 {
+		return fmt.Errorf("more than one package selected: %v", pkgs)
+	}
+
+	// TODO: add in external input. Right now we assume that all files are
+	// manually created and stored in the textdata directory.
+
+	// Build up index of translations and original messages.
+	extracted := Locale{}
+	translations := map[language.Tag]map[string]Message{}
+	languages := []language.Tag{}
+	langVars := []string{}
+	usedKeys := map[string]int{}
+
+	err = filepath.Walk(*dir, func(path string, f os.FileInfo, err error) error {
+		if err != nil {
+			return wrap(err, "loading data")
+		}
+		if f.IsDir() {
+			return nil
+		}
+		if f.Name() == extractFile {
+			b, err := ioutil.ReadFile(path)
+			if err != nil {
+				return wrap(err, "read file failed")
+			}
+			if err := json.Unmarshal(b, &extracted); err != nil {
+				return wrap(err, "unmarshal source failed")
+			}
+			return nil
+		}
+		if f.Name() == outFile {
+			return nil
+		}
+		if !strings.HasSuffix(path, gotextSuffix) {
+			return nil
+		}
+		b, err := ioutil.ReadFile(path)
+		if err != nil {
+			return wrap(err, "read file failed")
+		}
+		var locale Locale
+		if err := json.Unmarshal(b, &locale); err != nil {
+			return wrap(err, "parsing translation file failed")
+		}
+		tag := locale.Language
+		if _, ok := translations[tag]; !ok {
+			translations[tag] = map[string]Message{}
+			languages = append(languages, tag)
+		}
+		for _, m := range locale.Messages {
+			if !m.Translation.IsEmpty() {
+				for _, id := range m.ID {
+					if _, ok := translations[tag][id]; ok {
+						logf("Duplicate translation in locale %q for message %q", tag, id)
+					}
+					translations[tag][id] = m
+				}
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+
+	// Verify completeness and register keys.
+	internal.SortTags(languages)
+
+	for _, tag := range languages {
+		langVars = append(langVars, strings.Replace(tag.String(), "-", "_", -1))
+		dict := translations[tag]
+		for _, msg := range extracted.Messages {
+			for _, id := range msg.ID {
+				if trans, ok := dict[id]; ok && !trans.Translation.IsEmpty() {
+					if _, ok := usedKeys[msg.Key]; !ok {
+						usedKeys[msg.Key] = len(usedKeys)
+					}
+					break
+				}
+				// TODO: log missing entry.
+				logf("%s: Missing entry for %q.", tag, id)
+			}
+		}
+	}
+
+	w := gen.NewCodeWriter()
+
+	x := &struct {
+		Fallback  language.Tag
+		Languages []string
+	}{
+		Fallback:  extracted.Language,
+		Languages: langVars,
+	}
+
+	if err := lookup.Execute(w, x); err != nil {
+		return wrap(err, "error")
+	}
+
+	keyToIndex := []string{}
+	for k := range usedKeys {
+		keyToIndex = append(keyToIndex, k)
+	}
+	sort.Strings(keyToIndex)
+	fmt.Fprint(w, "var messageKeyToIndex = map[string]int{\n")
+	for _, k := range keyToIndex {
+		fmt.Fprintf(w, "%q: %d,\n", k, usedKeys[k])
+	}
+	fmt.Fprint(w, "}\n\n")
+
+	for i, tag := range languages {
+		dict := translations[tag]
+		a := make([]string, len(usedKeys))
+		for _, msg := range extracted.Messages {
+			for _, id := range msg.ID {
+				if trans, ok := dict[id]; ok && !trans.Translation.IsEmpty() {
+					m, err := assemble(&msg, &trans.Translation)
+					if err != nil {
+						return wrap(err, "error")
+					}
+					// TODO: support macros.
+					data, err := catmsg.Compile(tag, nil, m)
+					if err != nil {
+						return wrap(err, "error")
+					}
+					key := usedKeys[msg.Key]
+					if d := a[key]; d != "" && d != data {
+						logf("Duplicate non-consistent translation for key %q, picking the one for message %q", msg.Key, id)
+					}
+					a[key] = string(data)
+					break
+				}
+			}
+		}
+		index := []uint32{0}
+		p := 0
+		for _, s := range a {
+			p += len(s)
+			index = append(index, uint32(p))
+		}
+
+		w.WriteVar(langVars[i]+"Index", index)
+		w.WriteConst(langVars[i]+"Data", strings.Join(a, ""))
+	}
+
+	pkg := pkgs[0].Pkg.Name()
+	if *out == "" {
+		if _, err = w.WriteGo(os.Stdout, pkg); err != nil {
+			return wrap(err, "could not write go file")
+		}
+	} else {
+		w.WriteGoFile(*out, pkg)
+	}
+
+	return nil
+}
+
+func assemble(m *Message, t *Text) (msg catmsg.Message, err error) {
+	keys := []string{}
+	for k := range t.Var {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	var a []catmsg.Message
+	for _, k := range keys {
+		t := t.Var[k]
+		m, err := assemble(m, &t)
+		if err != nil {
+			return nil, err
+		}
+		a = append(a, &catmsg.Var{Name: k, Message: m})
+	}
+	if t.Select != nil {
+		s, err := assembleSelect(m, t.Select)
+		if err != nil {
+			return nil, err
+		}
+		a = append(a, s)
+	}
+	if t.Msg != "" {
+		sub, err := m.Substitute(t.Msg)
+		if err != nil {
+			return nil, err
+		}
+		a = append(a, catmsg.String(sub))
+	}
+	switch len(a) {
+	case 0:
+		return nil, errorf("generate: empty message")
+	case 1:
+		return a[0], nil
+	default:
+		return catmsg.FirstOf(a), nil
+
+	}
+}
+
+func assembleSelect(m *Message, s *Select) (msg catmsg.Message, err error) {
+	cases := []string{}
+	for c := range s.Cases {
+		cases = append(cases, c)
+	}
+	sortCases(cases)
+
+	caseMsg := []interface{}{}
+	for _, c := range cases {
+		cm := s.Cases[c]
+		m, err := assemble(m, &cm)
+		if err != nil {
+			return nil, err
+		}
+		caseMsg = append(caseMsg, c, m)
+	}
+
+	ph := m.Placeholder(s.Arg)
+
+	switch s.Feature {
+	case "plural":
+		// TODO: only printf-style selects are supported as of yet.
+		return plural.Selectf(ph.ArgNum, ph.String, caseMsg...), nil
+	}
+	return nil, errorf("unknown feature type %q", s.Feature)
+}
+
+func sortCases(cases []string) {
+	// TODO: implement full interface.
+	sort.Slice(cases, func(i, j int) bool {
+		if cases[j] == "other" && cases[i] != "other" {
+			return true
+		}
+		// the following code relies on '<' < '=' < any letter.
+		return cmpNumeric(cases[i], cases[j]) == -1
+	})
+}
+
+var cmpNumeric = collate.New(language.Und, collate.Numeric).CompareString
+
+var lookup = template.Must(template.New("gen").Parse(`
+import (
+	"golang.org/x/text/language"
+	"golang.org/x/text/message"
+	"golang.org/x/text/message/catalog"
+)
+
+type dictionary struct {
+	index []uint32
+	data  string
+}
+
+func (d *dictionary) Lookup(key string) (data string, ok bool) {
+	p := messageKeyToIndex[key]
+	start, end := d.index[p], d.index[p+1]
+	if start == end {
+		return "", false
+	}
+	return d.data[start:end], true
+}
+
+func init() {
+	dict := map[string]catalog.Dictionary{
+		{{range .Languages}}"{{.}}": &dictionary{index: {{.}}Index, data: {{.}}Data },
+		{{end}}
+	}
+	fallback := language.MustParse("{{.Fallback}}")
+	cat, err := catalog.NewFromMap(dict, catalog.Fallback(fallback))
+	if err != nil {
+		panic(err)
+	}
+	message.DefaultCatalog = cat
+}
+
+`))

diff --git a/message/pipeline/main.go b/message/pipeline/main.go
new file mode 100644
index 0000000..f3f50d7
--- /dev/null
+++ b/message/pipeline/main.go

@@ -0,0 +1,352 @@
+// Copyright 2016 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.
+
+//go:generate go build -o gotext.latest
+//go:generate ./gotext.latest help gendocumentation
+//go:generate rm gotext.latest
+
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"flag"
+	"fmt"
+	"go/build"
+	"go/format"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"strings"
+	"sync"
+	"text/template"
+	"unicode"
+	"unicode/utf8"
+
+	"golang.org/x/text/language"
+	"golang.org/x/tools/go/buildutil"
+)
+
+func init() {
+	flag.Var((*buildutil.TagsFlag)(&build.Default.BuildTags), "tags", buildutil.TagsFlagDoc)
+}
+
+var dir = flag.String("dir", "locales", "default subdirectory to store translation files")
+
+// NOTE: the Command struct is copied from the go tool in core.
+
+// A Command is an implementation of a go command
+// like go build or go fix.
+type Command struct {
+	// Run runs the command.
+	// The args are the arguments after the command name.
+	Run func(cmd *Command, args []string) error
+
+	// UsageLine is the one-line usage message.
+	// The first word in the line is taken to be the command name.
+	UsageLine string
+
+	// Short is the short description shown in the 'go help' output.
+	Short string
+
+	// Long is the long message shown in the 'go help <this-command>' output.
+	Long string
+
+	// Flag is a set of flags specific to this command.
+	Flag flag.FlagSet
+}
+
+// Name returns the command's name: the first word in the usage line.
+func (c *Command) Name() string {
+	name := c.UsageLine
+	i := strings.Index(name, " ")
+	if i >= 0 {
+		name = name[:i]
+	}
+	return name
+}
+
+func (c *Command) Usage() {
+	fmt.Fprintf(os.Stderr, "usage: %s\n\n", c.UsageLine)
+	fmt.Fprintf(os.Stderr, "%s\n", strings.TrimSpace(c.Long))
+	os.Exit(2)
+}
+
+// Runnable reports whether the command can be run; otherwise
+// it is a documentation pseudo-command such as importpath.
+func (c *Command) Runnable() bool {
+	return c.Run != nil
+}
+
+// Commands lists the available commands and help topics.
+// The order here is the order in which they are printed by 'go help'.
+var commands = []*Command{
+	cmdExtract,
+	cmdRewrite,
+	cmdGenerate,
+	// TODO:
+	// - update: full-cycle update of extraction, sending, and integration
+	// - report: report of freshness of translations
+}
+
+var exitStatus = 0
+var exitMu sync.Mutex
+
+func setExitStatus(n int) {
+	exitMu.Lock()
+	if exitStatus < n {
+		exitStatus = n
+	}
+	exitMu.Unlock()
+}
+
+var origEnv []string
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+	log.SetFlags(0)
+
+	args := flag.Args()
+	if len(args) < 1 {
+		usage()
+	}
+
+	if args[0] == "help" {
+		help(args[1:])
+		return
+	}
+
+	for _, cmd := range commands {
+		if cmd.Name() == args[0] && cmd.Runnable() {
+			cmd.Flag.Usage = func() { cmd.Usage() }
+			cmd.Flag.Parse(args[1:])
+			args = cmd.Flag.Args()
+			if err := cmd.Run(cmd, args); err != nil {
+				fatalf("gotext: %+v", err)
+			}
+			exit()
+			return
+		}
+	}
+
+	fmt.Fprintf(os.Stderr, "gotext: unknown subcommand %q\nRun 'go help' for usage.\n", args[0])
+	setExitStatus(2)
+	exit()
+}
+
+var usageTemplate = `gotext is a tool for managing text in Go source code.
+
+Usage:
+
+	gotext command [arguments]
+
+The commands are:
+{{range .}}{{if .Runnable}}
+	{{.Name | printf "%-11s"}} {{.Short}}{{end}}{{end}}
+
+Use "go help [command]" for more information about a command.
+
+Additional help topics:
+{{range .}}{{if not .Runnable}}
+	{{.Name | printf "%-11s"}} {{.Short}}{{end}}{{end}}
+
+Use "gotext help [topic]" for more information about that topic.
+
+`
+
+var helpTemplate = `{{if .Runnable}}usage: go {{.UsageLine}}
+
+{{end}}{{.Long | trim}}
+`
+
+var documentationTemplate = `{{range .}}{{if .Short}}{{.Short | capitalize}}
+
+{{end}}{{if .Runnable}}Usage:
+
+	go {{.UsageLine}}
+
+{{end}}{{.Long | trim}}
+
+
+{{end}}`
+
+// commentWriter writes a Go comment to the underlying io.Writer,
+// using line comment form (//).
+type commentWriter struct {
+	W            io.Writer
+	wroteSlashes bool // Wrote "//" at the beginning of the current line.
+}
+
+func (c *commentWriter) Write(p []byte) (int, error) {
+	var n int
+	for i, b := range p {
+		if !c.wroteSlashes {
+			s := "//"
+			if b != '\n' {
+				s = "// "
+			}
+			if _, err := io.WriteString(c.W, s); err != nil {
+				return n, err
+			}
+			c.wroteSlashes = true
+		}
+		n0, err := c.W.Write(p[i : i+1])
+		n += n0
+		if err != nil {
+			return n, err
+		}
+		if b == '\n' {
+			c.wroteSlashes = false
+		}
+	}
+	return len(p), nil
+}
+
+// An errWriter wraps a writer, recording whether a write error occurred.
+type errWriter struct {
+	w   io.Writer
+	err error
+}
+
+func (w *errWriter) Write(b []byte) (int, error) {
+	n, err := w.w.Write(b)
+	if err != nil {
+		w.err = err
+	}
+	return n, err
+}
+
+// tmpl executes the given template text on data, writing the result to w.
+func tmpl(w io.Writer, text string, data interface{}) {
+	t := template.New("top")
+	t.Funcs(template.FuncMap{"trim": strings.TrimSpace, "capitalize": capitalize})
+	template.Must(t.Parse(text))
+	ew := &errWriter{w: w}
+	err := t.Execute(ew, data)
+	if ew.err != nil {
+		// I/O error writing. Ignore write on closed pipe.
+		if strings.Contains(ew.err.Error(), "pipe") {
+			os.Exit(1)
+		}
+		fatalf("writing output: %v", ew.err)
+	}
+	if err != nil {
+		panic(err)
+	}
+}
+
+func capitalize(s string) string {
+	if s == "" {
+		return s
+	}
+	r, n := utf8.DecodeRuneInString(s)
+	return string(unicode.ToTitle(r)) + s[n:]
+}
+
+func printUsage(w io.Writer) {
+	bw := bufio.NewWriter(w)
+	tmpl(bw, usageTemplate, commands)
+	bw.Flush()
+}
+
+func usage() {
+	printUsage(os.Stderr)
+	os.Exit(2)
+}
+
+// help implements the 'help' command.
+func help(args []string) {
+	if len(args) == 0 {
+		printUsage(os.Stdout)
+		// not exit 2: succeeded at 'go help'.
+		return
+	}
+	if len(args) != 1 {
+		fmt.Fprintf(os.Stderr, "usage: go help command\n\nToo many arguments given.\n")
+		os.Exit(2) // failed at 'go help'
+	}
+
+	arg := args[0]
+
+	// 'go help documentation' generates doc.go.
+	if strings.HasSuffix(arg, "documentation") {
+		w := &bytes.Buffer{}
+
+		fmt.Fprintln(w, "// Code generated by go generate. DO NOT EDIT.")
+		fmt.Fprintln(w)
+		buf := new(bytes.Buffer)
+		printUsage(buf)
+		usage := &Command{Long: buf.String()}
+		tmpl(&commentWriter{W: w}, documentationTemplate, append([]*Command{usage}, commands...))
+		fmt.Fprintln(w, "package main")
+		if arg == "gendocumentation" {
+			b, err := format.Source(w.Bytes())
+			if err != nil {
+				logf("Could not format generated docs: %v\n", err)
+			}
+			if err := ioutil.WriteFile("doc.go", b, 0666); err != nil {
+				logf("Could not create file alldocs.go: %v\n", err)
+			}
+		} else {
+			fmt.Println(w.String())
+		}
+		return
+	}
+
+	for _, cmd := range commands {
+		if cmd.Name() == arg {
+			tmpl(os.Stdout, helpTemplate, cmd)
+			// not exit 2: succeeded at 'go help cmd'.
+			return
+		}
+	}
+
+	fmt.Fprintf(os.Stderr, "Unknown help topic %#q.  Run 'go help'.\n", arg)
+	os.Exit(2) // failed at 'go help cmd'
+}
+
+func getLangs() (tags []language.Tag) {
+	for _, t := range strings.Split(*lang, ",") {
+		if t == "" {
+			continue
+		}
+		tag, err := language.Parse(t)
+		if err != nil {
+			fatalf("gotext: could not parse language %q: %v", t, err)
+		}
+		tags = append(tags, tag)
+	}
+	return tags
+}
+
+var atexitFuncs []func()
+
+func atexit(f func()) {
+	atexitFuncs = append(atexitFuncs, f)
+}
+
+func exit() {
+	for _, f := range atexitFuncs {
+		f()
+	}
+	os.Exit(exitStatus)
+}
+
+func fatalf(format string, args ...interface{}) {
+	logf(format, args...)
+	exit()
+}
+
+func logf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+	setExitStatus(1)
+}
+
+func exitIfErrors() {
+	if exitStatus != 0 {
+		exit()
+	}
+}

diff --git a/message/pipeline/message.go b/message/pipeline/message.go
new file mode 100644
index 0000000..990ba52
--- /dev/null
+++ b/message/pipeline/message.go

@@ -0,0 +1,222 @@
+// Copyright 2016 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 (
+	"encoding/json"
+	"strings"
+
+	"golang.org/x/text/language"
+)
+
+// TODO: these definitions should be moved to a package so that the can be used
+// by other tools.
+
+// The file contains the structures used to define translations of a certain
+// messages.
+//
+// A translation may have multiple translations strings, or messages, depending
+// on the feature values of the various arguments. For instance, consider
+// a hypothetical translation from English to English, where the source defines
+// the format string "%d file(s) remaining".
+// See the examples directory for examples of extracted messages.
+
+// A Locale is used to store all information for a single locale. This type is
+// used both for extraction and injection.
+type Locale struct {
+	Language language.Tag    `json:"language"`
+	Messages []Message       `json:"messages"`
+	Macros   map[string]Text `json:"macros,omitempty"`
+}
+
+// A Message describes a message to be translated.
+type Message struct {
+	// ID contains a list of identifiers for the message.
+	ID IDList `json:"id"`
+	// Key is the string that is used to look up the message at runtime.
+	Key         string `json:"key"`
+	Meaning     string `json:"meaning,omitempty"`
+	Message     Text   `json:"message"`
+	Translation Text   `json:"translation"`
+
+	Comment           string `json:"comment,omitempty"`
+	TranslatorComment string `json:"translatorComment,omitempty"`
+
+	Placeholders []Placeholder `json:"placeholders,omitempty"`
+
+	// TODO: default placeholder syntax is {foo}. Allow alternative escaping
+	// like `foo`.
+
+	// Extraction information.
+	Position string `json:"position,omitempty"` // filePosition:line
+}
+
+// Placeholder reports the placeholder for the given ID if it is defined or nil
+// otherwise.
+func (m *Message) Placeholder(id string) *Placeholder {
+	for _, p := range m.Placeholders {
+		if p.ID == id {
+			return &p
+		}
+	}
+	return nil
+}
+
+// Substitute replaces placeholders in msg with their original value.
+func (m *Message) Substitute(msg string) (sub string, err error) {
+	last := 0
+	for i := 0; i < len(msg); {
+		pLeft := strings.IndexByte(msg[i:], '{')
+		if pLeft == -1 {
+			break
+		}
+		pLeft += i
+		pRight := strings.IndexByte(msg[pLeft:], '}')
+		if pRight == -1 {
+			return "", errorf("unmatched '}'")
+		}
+		pRight += pLeft
+		id := strings.TrimSpace(msg[pLeft+1 : pRight])
+		i = pRight + 1
+		if id != "" && id[0] == '$' {
+			continue
+		}
+		sub += msg[last:pLeft]
+		last = i
+		ph := m.Placeholder(id)
+		if ph == nil {
+			return "", errorf("unknown placeholder %q in message %q", id, msg)
+		}
+		sub += ph.String
+	}
+	sub += msg[last:]
+	return sub, err
+}
+
+// A Placeholder is a part of the message that should not be changed by a
+// translator. It can be used to hide or prettify format strings (e.g. %d or
+// {{.Count}}), hide HTML, or mark common names that should not be translated.
+type Placeholder struct {
+	// ID is the placeholder identifier without the curly braces.
+	ID string `json:"id"`
+
+	// String is the string with which to replace the placeholder. This may be a
+	// formatting string (for instance "%d" or "{{.Count}}") or a literal string
+	// (<div>).
+	String string `json:"string"`
+
+	Type           string `json:"type"`
+	UnderlyingType string `json:"underlyingType"`
+	// ArgNum and Expr are set if the placeholder is a substitution of an
+	// argument.
+	ArgNum int    `json:"argNum,omitempty"`
+	Expr   string `json:"expr,omitempty"`
+
+	Comment string `json:"comment,omitempty"`
+	Example string `json:"example,omitempty"`
+
+	// Features contains the features that are available for the implementation
+	// of this argument.
+	Features []Feature `json:"features,omitempty"`
+}
+
+// An argument contains information about the arguments passed to a message.
+type argument struct {
+	// ArgNum corresponds to the number that should be used for explicit argument indexes (e.g.
+	// "%[1]d").
+	ArgNum int `json:"argNum,omitempty"`
+
+	used           bool   // Used by Placeholder
+	Type           string `json:"type"`
+	UnderlyingType string `json:"underlyingType"`
+	Expr           string `json:"expr"`
+	Value          string `json:"value,omitempty"`
+	Comment        string `json:"comment,omitempty"`
+	Position       string `json:"position,omitempty"`
+}
+
+// Feature holds information about a feature that can be implemented by
+// an Argument.
+type Feature struct {
+	Type string `json:"type"` // Right now this is only gender and plural.
+
+	// TODO: possible values and examples for the language under consideration.
+
+}
+
+// Text defines a message to be displayed.
+type Text struct {
+	// Msg and Select contains the message to be displayed. Msg may be used as
+	// a fallback value if none of the select cases match.
+	Msg    string  `json:"msg,omitempty"`
+	Select *Select `json:"select,omitempty"`
+
+	// Var defines a map of variables that may be substituted in the selected
+	// message.
+	Var map[string]Text `json:"var,omitempty"`
+
+	// Example contains an example message formatted with default values.
+	Example string `json:"example,omitempty"`
+}
+
+// IsEmpty reports whether this Text can generate anything.
+func (t *Text) IsEmpty() bool {
+	return t.Msg == "" && t.Select == nil && t.Var == nil
+}
+
+// rawText erases the UnmarshalJSON method.
+type rawText Text
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (t *Text) UnmarshalJSON(b []byte) error {
+	if b[0] == '"' {
+		return json.Unmarshal(b, &t.Msg)
+	}
+	return json.Unmarshal(b, (*rawText)(t))
+}
+
+// MarshalJSON implements json.Marshaler.
+func (t *Text) MarshalJSON() ([]byte, error) {
+	if t.Select == nil && t.Var == nil && t.Example == "" {
+		return json.Marshal(t.Msg)
+	}
+	return json.Marshal((*rawText)(t))
+}
+
+// IDList is a set identifiers that each may refer to possibly different
+// versions of the same message. When looking up a messages, the first
+// identifier in the list takes precedence.
+type IDList []string
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (id *IDList) UnmarshalJSON(b []byte) error {
+	if b[0] == '"' {
+		*id = []string{""}
+		return json.Unmarshal(b, &((*id)[0]))
+	}
+	return json.Unmarshal(b, (*[]string)(id))
+}
+
+// MarshalJSON implements json.Marshaler.
+func (id *IDList) MarshalJSON() ([]byte, error) {
+	if len(*id) == 1 {
+		return json.Marshal((*id)[0])
+	}
+	return json.Marshal((*[]string)(id))
+}
+
+// Select selects a Text based on the feature value associated with a feature of
+// a certain argument.
+type Select struct {
+	Feature string          `json:"feature"` // Name of Feature type (e.g plural)
+	Arg     string          `json:"arg"`     // The placeholder ID
+	Cases   map[string]Text `json:"cases"`
+}
+
+// TODO: order matters, but can we derive the ordering from the case keys?
+// type Case struct {
+// 	Key   string `json:"key"`
+// 	Value Text   `json:"value"`
+// }

diff --git a/message/pipeline/rewrite.go b/message/pipeline/rewrite.go
new file mode 100644
index 0000000..f4641c8
--- /dev/null
+++ b/message/pipeline/rewrite.go

@@ -0,0 +1,287 @@
+// Copyright 2017 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"
+	"fmt"
+	"go/ast"
+	"go/constant"
+	"go/format"
+	"go/token"
+	"os"
+	"strings"
+
+	"golang.org/x/tools/go/loader"
+)
+
+const printerType = "golang.org/x/text/message.Printer"
+
+// TODO:
+// - merge information into existing files
+// - handle different file formats (PO, XLIFF)
+// - handle features (gender, plural)
+// - message rewriting
+
+func init() {
+	overwrite = cmdRewrite.Flag.Bool("w", false, "write files in place")
+}
+
+var (
+	overwrite *bool
+)
+
+var cmdRewrite = &Command{
+	Run:       runRewrite,
+	UsageLine: "rewrite <package>",
+	Short:     "rewrites fmt functions to use a message Printer",
+	Long: `
+rewrite is typically done once for a project. It rewrites all usages of
+fmt to use x/text's message package whenever a message.Printer is in scope.
+It rewrites Print and Println calls with constant strings to the equivalent
+using Printf to allow translators to reorder arguments.
+`,
+}
+
+func runRewrite(cmd *Command, args []string) error {
+	conf := &loader.Config{
+		AllowErrors: true, // Allow unused instances of message.Printer.
+	}
+	prog, err := loadPackages(conf, args)
+	if err != nil {
+		return wrap(err, "")
+	}
+
+	for _, info := range prog.InitialPackages() {
+		for _, f := range info.Files {
+			// Associate comments with nodes.
+
+			// Pick up initialized Printers at the package level.
+			r := rewriter{info: info, conf: conf}
+			for _, n := range info.InitOrder {
+				if t := r.info.Types[n.Rhs].Type.String(); strings.HasSuffix(t, printerType) {
+					r.printerVar = n.Lhs[0].Name()
+				}
+			}
+
+			ast.Walk(&r, f)
+
+			w := os.Stdout
+			if *overwrite {
+				var err error
+				if w, err = os.Create(conf.Fset.File(f.Pos()).Name()); err != nil {
+					return wrap(err, "open failed")
+				}
+			}
+
+			if err := format.Node(w, conf.Fset, f); err != nil {
+				return wrap(err, "go format failed")
+			}
+		}
+	}
+
+	return nil
+}
+
+type rewriter struct {
+	info       *loader.PackageInfo
+	conf       *loader.Config
+	printerVar string
+}
+
+// print returns Go syntax for the specified node.
+func (r *rewriter) print(n ast.Node) string {
+	var buf bytes.Buffer
+	format.Node(&buf, r.conf.Fset, n)
+	return buf.String()
+}
+
+func (r *rewriter) Visit(n ast.Node) ast.Visitor {
+	// Save the state by scope.
+	if _, ok := n.(*ast.BlockStmt); ok {
+		r := *r
+		return &r
+	}
+	// Find Printers created by assignment.
+	stmt, ok := n.(*ast.AssignStmt)
+	if ok {
+		for _, v := range stmt.Lhs {
+			if r.printerVar == r.print(v) {
+				r.printerVar = ""
+			}
+		}
+		for i, v := range stmt.Rhs {
+			if t := r.info.Types[v].Type.String(); strings.HasSuffix(t, printerType) {
+				r.printerVar = r.print(stmt.Lhs[i])
+				return r
+			}
+		}
+	}
+	// Find Printers created by variable declaration.
+	spec, ok := n.(*ast.ValueSpec)
+	if ok {
+		for _, v := range spec.Names {
+			if r.printerVar == r.print(v) {
+				r.printerVar = ""
+			}
+		}
+		for i, v := range spec.Values {
+			if t := r.info.Types[v].Type.String(); strings.HasSuffix(t, printerType) {
+				r.printerVar = r.print(spec.Names[i])
+				return r
+			}
+		}
+	}
+	if r.printerVar == "" {
+		return r
+	}
+	call, ok := n.(*ast.CallExpr)
+	if !ok {
+		return r
+	}
+
+	// TODO: Handle literal values?
+	sel, ok := call.Fun.(*ast.SelectorExpr)
+	if !ok {
+		return r
+	}
+	meth := r.info.Selections[sel]
+
+	source := r.print(sel.X)
+	fun := r.print(sel.Sel)
+	if meth != nil {
+		source = meth.Recv().String()
+		fun = meth.Obj().Name()
+	}
+
+	// TODO: remove cheap hack and check if the type either
+	// implements some interface or is specifically of type
+	// "golang.org/x/text/message".Printer.
+	m, ok := rewriteFuncs[source]
+	if !ok {
+		return r
+	}
+
+	rewriteType, ok := m[fun]
+	if !ok {
+		return r
+	}
+	ident := ast.NewIdent(r.printerVar)
+	ident.NamePos = sel.X.Pos()
+	sel.X = ident
+	if rewriteType.method != "" {
+		sel.Sel.Name = rewriteType.method
+	}
+
+	// Analyze arguments.
+	argn := rewriteType.arg
+	if rewriteType.format || argn >= len(call.Args) {
+		return r
+	}
+	hasConst := false
+	for _, a := range call.Args[argn:] {
+		if v := r.info.Types[a].Value; v != nil && v.Kind() == constant.String {
+			hasConst = true
+			break
+		}
+	}
+	if !hasConst {
+		return r
+	}
+	sel.Sel.Name = rewriteType.methodf
+
+	// We are done if there is only a single string that does not need to be
+	// escaped.
+	if len(call.Args) == 1 {
+		s, ok := constStr(r.info, call.Args[0])
+		if ok && !strings.Contains(s, "%") && !rewriteType.newLine {
+			return r
+		}
+	}
+
+	// Rewrite arguments as format string.
+	expr := &ast.BasicLit{
+		ValuePos: call.Lparen,
+		Kind:     token.STRING,
+	}
+	newArgs := append(call.Args[:argn:argn], expr)
+	newStr := []string{}
+	for i, a := range call.Args[argn:] {
+		if s, ok := constStr(r.info, a); ok {
+			newStr = append(newStr, strings.Replace(s, "%", "%%", -1))
+		} else {
+			newStr = append(newStr, "%v")
+			newArgs = append(newArgs, call.Args[argn+i])
+		}
+	}
+	s := strings.Join(newStr, rewriteType.sep)
+	if rewriteType.newLine {
+		s += "\n"
+	}
+	expr.Value = fmt.Sprintf("%q", s)
+
+	call.Args = newArgs
+
+	// TODO: consider creating an expression instead of a constant string and
+	// then wrapping it in an escape function or so:
+	// call.Args[argn+i] = &ast.CallExpr{
+	// 		Fun: &ast.SelectorExpr{
+	// 			X:   ast.NewIdent("message"),
+	// 			Sel: ast.NewIdent("Lookup"),
+	// 		},
+	// 		Args: []ast.Expr{a},
+	// 	}
+	// }
+
+	return r
+}
+
+type rewriteType struct {
+	// method is the name of the equivalent method on a printer, or "" if it is
+	// the same.
+	method string
+
+	// methodf is the method to use if the arguments can be rewritten as a
+	// arguments to a printf-style call.
+	methodf string
+
+	// format is true if the method takes a formatting string followed by
+	// substitution arguments.
+	format bool
+
+	// arg indicates the position of the argument to extract. If all is
+	// positive, all arguments from this argument onwards needs to be extracted.
+	arg int
+
+	sep     string
+	newLine bool
+}
+
+// rewriteFuncs list functions that can be directly mapped to the printer
+// functions of the message package.
+var rewriteFuncs = map[string]map[string]rewriteType{
+	// TODO: Printer -> *golang.org/x/text/message.Printer
+	"fmt": {
+		"Print":  rewriteType{methodf: "Printf"},
+		"Sprint": rewriteType{methodf: "Sprintf"},
+		"Fprint": rewriteType{methodf: "Fprintf"},
+
+		"Println":  rewriteType{methodf: "Printf", sep: " ", newLine: true},
+		"Sprintln": rewriteType{methodf: "Sprintf", sep: " ", newLine: true},
+		"Fprintln": rewriteType{methodf: "Fprintf", sep: " ", newLine: true},
+
+		"Printf":  rewriteType{method: "Printf", format: true},
+		"Sprintf": rewriteType{method: "Sprintf", format: true},
+		"Fprintf": rewriteType{method: "Fprintf", format: true},
+	},
+}
+
+func constStr(info *loader.PackageInfo, e ast.Expr) (s string, ok bool) {
+	v := info.Types[e].Value
+	if v == nil || v.Kind() != constant.String {
+		return "", false
+	}
+	return constant.StringVal(v), true
+}