internal/imports/imports.go - tools.git - Git at Google

 // 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.

 //go:generate go run mkstdlib.go

 // Package imports implements a Go pretty-printer (like package "go/format")
 // that also adds or removes import statements as necessary.
 package imports

 import (
 	"bufio"
 	"bytes"
 	"context"
 	"fmt"
 	"go/ast"
 	"go/build"
 	"go/format"
 	"go/parser"
 	"go/printer"
 	"go/token"
 	"io"
 	"io/ioutil"
 	"log"
 	"os"
 	"regexp"
 	"strconv"
 	"strings"

 	"golang.org/x/tools/go/ast/astutil"
 )

 // Options is golang.org/x/tools/imports.Options with extra internal-only options.
 type Options struct {
 	Env *ProcessEnv // The environment to use. Note: this contains the cached module and filesystem state.

 	Fragment  bool // Accept fragment 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)

 	FormatOnly bool // Disable the insertion and deletion of imports
 }

 // Process implements golang.org/x/tools/imports.Process with explicit context in env.
 func Process(filename string, src []byte, opt *Options) (formatted []byte, err error) {
 	src, opt, err = initialize(filename, src, opt)
 	if err != nil {
 		return nil, err
 	}

 	fileSet := token.NewFileSet()
 	file, adjust, err := parse(fileSet, filename, src, opt)
 	if err != nil {
 		return nil, err
 	}

 	if !opt.FormatOnly {
 		if err := fixImports(fileSet, file, filename, opt.Env); err != nil {
 			return nil, err
 		}
 	}
 	return formatFile(fileSet, file, src, adjust, opt)
 }

 // FixImports returns a list of fixes to the imports that, when applied,
 // will leave the imports in the same state as Process.
 //
 // Note that filename's directory influences which imports can be chosen,
 // so it is important that filename be accurate.
 func FixImports(filename string, src []byte, opt *Options) (fixes []*ImportFix, err error) {
 	src, opt, err = initialize(filename, src, opt)
 	if err != nil {
 		return nil, err
 	}

 	fileSet := token.NewFileSet()
 	file, _, err := parse(fileSet, filename, src, opt)
 	if err != nil {
 		return nil, err
 	}

 	return getFixes(fileSet, file, filename, opt.Env)
 }

 // ApplyFixes applies all of the fixes to the file and formats it. extraMode
 // is added in when parsing the file.
 func ApplyFixes(fixes []*ImportFix, filename string, src []byte, opt *Options, extraMode parser.Mode) (formatted []byte, err error) {
 	src, opt, err = initialize(filename, src, opt)
 	if err != nil {
 		return nil, err
 	}

 	// Don't use parse() -- we don't care about fragments or statement lists
 	// here, and we need to work with unparseable files.
 	fileSet := token.NewFileSet()
 	parserMode := parser.Mode(0)
 	if opt.Comments {
 		parserMode |= parser.ParseComments
 	}
 	if opt.AllErrors {
 		parserMode |= parser.AllErrors
 	}
 	parserMode |= extraMode

 	file, err := parser.ParseFile(fileSet, filename, src, parserMode)
 	if file == nil {
 		return nil, err
 	}

 	// Apply the fixes to the file.
 	apply(fileSet, file, fixes)

 	return formatFile(fileSet, file, src, nil, opt)
 }

 // GetAllCandidates gets all of the packages starting with prefix that can be
 // imported by filename, sorted by import path.
 func GetAllCandidates(ctx context.Context, callback func(ImportFix), searchPrefix, filename, filePkg string, opt *Options) error {
 	_, opt, err := initialize(filename, []byte{}, opt)
 	if err != nil {
 		return err
 	}
 	return getAllCandidates(ctx, callback, searchPrefix, filename, filePkg, opt.Env)
 }

 // GetPackageExports returns all known packages with name pkg and their exports.
 func GetPackageExports(ctx context.Context, callback func(PackageExport), searchPkg, filename, filePkg string, opt *Options) error {
 	_, opt, err := initialize(filename, []byte{}, opt)
 	if err != nil {
 		return err
 	}
 	return getPackageExports(ctx, callback, searchPkg, filename, filePkg, opt.Env)
 }

 // initialize sets the values for opt and src.
 // If they are provided, they are not changed. Otherwise opt is set to the
 // default values and src is read from the file system.
 func initialize(filename string, src []byte, opt *Options) ([]byte, *Options, error) {
 	// Use defaults if opt is nil.
 	if opt == nil {
 		opt = &Options{Comments: true, TabIndent: true, TabWidth: 8}
 	}

 	// Set the env if the user has not provided it.
 	if opt.Env == nil {
 		opt.Env = &ProcessEnv{
 			GOPATH:      build.Default.GOPATH,
 			GOROOT:      build.Default.GOROOT,
 			GOFLAGS:     os.Getenv("GOFLAGS"),
 			GO111MODULE: os.Getenv("GO111MODULE"),
 			GOPROXY:     os.Getenv("GOPROXY"),
 			GOSUMDB:     os.Getenv("GOSUMDB"),
 		}
 	}

 	// Set the logger if the user has not provided it.
 	if opt.Env.Logf == nil {
 		opt.Env.Logf = log.Printf
 	}

 	if src == nil {
 		b, err := ioutil.ReadFile(filename)
 		if err != nil {
 			return nil, nil, err
 		}
 		src = b
 	}

 	return src, opt, nil
 }

 func formatFile(fileSet *token.FileSet, file *ast.File, src []byte, adjust func(orig []byte, src []byte) []byte, opt *Options) ([]byte, error) {
 	mergeImports(opt.Env, fileSet, file)
 	sortImports(opt.Env, fileSet, file)
 	imps := astutil.Imports(fileSet, file)
 	var spacesBefore []string // import paths we need spaces before
 	for _, impSection := range imps {
 		// Within each block of contiguous imports, see if any
 		// import lines are in different group numbers. If so,
 		// we'll need to put a space between them so it's
 		// compatible with gofmt.
 		lastGroup := -1
 		for _, importSpec := range impSection {
 			importPath, _ := strconv.Unquote(importSpec.Path.Value)
 			groupNum := importGroup(opt.Env, 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, err = addImportSpaces(bytes.NewReader(out), spacesBefore)
 		if err != nil {
 			return nil, err
 		}
 	}

 	out, err = format.Source(out)
 	if err != nil {
 		return nil, err
 	}
 	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 parse errors are on
 	// the correct line.
 	const prefix = "package main;"
 	psrc := append([]byte(prefix), src...)
 	file, err = parser.ParseFile(fset, filename, psrc, parserMode)
 	if err == nil {
 		// Gofmt will turn the ; into a \n.
 		// Do that ourselves now and update the file contents,
 		// so that positions and line numbers are correct going forward.
 		psrc[len(prefix)-1] = '\n'
 		fset.File(file.Package).SetLinesForContent(psrc)

 		// If a main function exists, we will assume this is a main
 		// package and leave the file.
 		if containsMainFunc(file) {
 			return file, nil, nil
 		}

 		adjust := func(orig, src []byte) []byte {
 			// Remove the package clause.
 			src = src[len(prefix):]
 			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
 }

 // containsMainFunc checks if a file contains a function declaration with the
 // function signature 'func main()'
 func containsMainFunc(file *ast.File) bool {
 	for _, decl := range file.Decls {
 		if f, ok := decl.(*ast.FuncDecl); ok {
 			if f.Name.Name != "main" {
 				continue
 			}

 			if len(f.Type.Params.List) != 0 {
 				continue
 			}

 			if f.Type.Results != nil && len(f.Type.Results.List) != 0 {
 				continue
 			}

 			return true
 		}
 	}

 	return false
 }

 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, error) {
 	var out bytes.Buffer
 	in := bufio.NewReader(r)
 	inImports := false
 	done := false
 	for {
 		s, err := in.ReadString('\n')
 		if err == io.EOF {
 			break
 		} else if err != nil {
 			return nil, err
 		}

 		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] == breaks[0] {
 					out.WriteByte('\n')
 					breaks = breaks[1:]
 				}
 			}
 		}

 		fmt.Fprint(&out, s)
 	}
 	return out.Bytes(), nil
 }
	// 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.

	//go:generate go run mkstdlib.go

	// Package imports implements a Go pretty-printer (like package "go/format")
	// that also adds or removes import statements as necessary.
	package imports

	import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"go/ast"
	"go/build"
	"go/format"
	"go/parser"
	"go/printer"
	"go/token"
	"io"
	"io/ioutil"
	"log"
	"os"
	"regexp"
	"strconv"
	"strings"

	"golang.org/x/tools/go/ast/astutil"
	)

	// Options is golang.org/x/tools/imports.Options with extra internal-only options.
	type Options struct {
	Env *ProcessEnv // The environment to use. Note: this contains the cached module and filesystem state.

	Fragment bool // Accept fragment 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)

	FormatOnly bool // Disable the insertion and deletion of imports
	}

	// Process implements golang.org/x/tools/imports.Process with explicit context in env.
	func Process(filename string, src []byte, opt *Options) (formatted []byte, err error) {
	src, opt, err = initialize(filename, src, opt)
	if err != nil {
	return nil, err
	}

	fileSet := token.NewFileSet()
	file, adjust, err := parse(fileSet, filename, src, opt)
	if err != nil {
	return nil, err
	}

	if !opt.FormatOnly {
	if err := fixImports(fileSet, file, filename, opt.Env); err != nil {
	return nil, err
	}
	}
	return formatFile(fileSet, file, src, adjust, opt)
	}

	// FixImports returns a list of fixes to the imports that, when applied,
	// will leave the imports in the same state as Process.
	//
	// Note that filename's directory influences which imports can be chosen,
	// so it is important that filename be accurate.
	func FixImports(filename string, src []byte, opt Options) (fixes []ImportFix, err error) {
	src, opt, err = initialize(filename, src, opt)
	if err != nil {
	return nil, err
	}

	fileSet := token.NewFileSet()
	file, _, err := parse(fileSet, filename, src, opt)
	if err != nil {
	return nil, err
	}

	return getFixes(fileSet, file, filename, opt.Env)
	}

	// ApplyFixes applies all of the fixes to the file and formats it. extraMode
	// is added in when parsing the file.
	func ApplyFixes(fixes []ImportFix, filename string, src []byte, opt Options, extraMode parser.Mode) (formatted []byte, err error) {
	src, opt, err = initialize(filename, src, opt)
	if err != nil {
	return nil, err
	}

	// Don't use parse() -- we don't care about fragments or statement lists
	// here, and we need to work with unparseable files.
	fileSet := token.NewFileSet()
	parserMode := parser.Mode(0)
	if opt.Comments {
	parserMode \|= parser.ParseComments
	}
	if opt.AllErrors {
	parserMode \|= parser.AllErrors
	}
	parserMode \|= extraMode

	file, err := parser.ParseFile(fileSet, filename, src, parserMode)
	if file == nil {
	return nil, err
	}

	// Apply the fixes to the file.
	apply(fileSet, file, fixes)

	return formatFile(fileSet, file, src, nil, opt)
	}

	// GetAllCandidates gets all of the packages starting with prefix that can be
	// imported by filename, sorted by import path.
	func GetAllCandidates(ctx context.Context, callback func(ImportFix), searchPrefix, filename, filePkg string, opt *Options) error {
	_, opt, err := initialize(filename, []byte{}, opt)
	if err != nil {
	return err
	}
	return getAllCandidates(ctx, callback, searchPrefix, filename, filePkg, opt.Env)
	}

	// GetPackageExports returns all known packages with name pkg and their exports.
	func GetPackageExports(ctx context.Context, callback func(PackageExport), searchPkg, filename, filePkg string, opt *Options) error {
	_, opt, err := initialize(filename, []byte{}, opt)
	if err != nil {
	return err
	}
	return getPackageExports(ctx, callback, searchPkg, filename, filePkg, opt.Env)
	}

	// initialize sets the values for opt and src.
	// If they are provided, they are not changed. Otherwise opt is set to the
	// default values and src is read from the file system.
	func initialize(filename string, src []byte, opt Options) ([]byte, Options, error) {
	// Use defaults if opt is nil.
	if opt == nil {
	opt = &Options{Comments: true, TabIndent: true, TabWidth: 8}
	}

	// Set the env if the user has not provided it.
	if opt.Env == nil {
	opt.Env = &ProcessEnv{
	GOPATH: build.Default.GOPATH,
	GOROOT: build.Default.GOROOT,
	GOFLAGS: os.Getenv("GOFLAGS"),
	GO111MODULE: os.Getenv("GO111MODULE"),
	GOPROXY: os.Getenv("GOPROXY"),
	GOSUMDB: os.Getenv("GOSUMDB"),
	}
	}

	// Set the logger if the user has not provided it.
	if opt.Env.Logf == nil {
	opt.Env.Logf = log.Printf
	}

	if src == nil {
	b, err := ioutil.ReadFile(filename)
	if err != nil {
	return nil, nil, err
	}
	src = b
	}

	return src, opt, nil
	}

	func formatFile(fileSet token.FileSet, file ast.File, src []byte, adjust func(orig []byte, src []byte) []byte, opt *Options) ([]byte, error) {
	mergeImports(opt.Env, fileSet, file)
	sortImports(opt.Env, fileSet, file)
	imps := astutil.Imports(fileSet, file)
	var spacesBefore []string // import paths we need spaces before
	for _, impSection := range imps {
	// Within each block of contiguous imports, see if any
	// import lines are in different group numbers. If so,
	// we'll need to put a space between them so it's
	// compatible with gofmt.
	lastGroup := -1
	for _, importSpec := range impSection {
	importPath, _ := strconv.Unquote(importSpec.Path.Value)
	groupNum := importGroup(opt.Env, 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, err = addImportSpaces(bytes.NewReader(out), spacesBefore)
	if err != nil {
	return nil, err
	}
	}

	out, err = format.Source(out)
	if err != nil {
	return nil, err
	}
	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 parse errors are on
	// the correct line.
	const prefix = "package main;"
	psrc := append([]byte(prefix), src...)
	file, err = parser.ParseFile(fset, filename, psrc, parserMode)
	if err == nil {
	// Gofmt will turn the ; into a \n.
	// Do that ourselves now and update the file contents,
	// so that positions and line numbers are correct going forward.
	psrc[len(prefix)-1] = '\n'
	fset.File(file.Package).SetLinesForContent(psrc)

	// If a main function exists, we will assume this is a main
	// package and leave the file.
	if containsMainFunc(file) {
	return file, nil, nil
	}

	adjust := func(orig, src []byte) []byte {
	// Remove the package clause.
	src = src[len(prefix):]
	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
	}

	// containsMainFunc checks if a file contains a function declaration with the
	// function signature 'func main()'
	func containsMainFunc(file *ast.File) bool {
	for _, decl := range file.Decls {
	if f, ok := decl.(*ast.FuncDecl); ok {
	if f.Name.Name != "main" {
	continue
	}

	if len(f.Type.Params.List) != 0 {
	continue
	}

	if f.Type.Results != nil && len(f.Type.Results.List) != 0 {
	continue
	}

	return true
	}
	}

	return false
	}

	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, error) {
	var out bytes.Buffer
	in := bufio.NewReader(r)
	inImports := false
	done := false
	for {
	s, err := in.ReadString('\n')
	if err == io.EOF {
	break
	} else if err != nil {
	return nil, err
	}

	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] == breaks[0] {
	out.WriteByte('\n')
	breaks = breaks[1:]
	}
	}
	}

	fmt.Fprint(&out, s)
	}
	return out.Bytes(), nil
	}