Use vendored go-swagger (#8087)

* Use vendored go-swagger

* vendor go-swagger

* revert un wanteed change

* remove un-needed GO111MODULE

* Update Makefile

Co-Authored-By: techknowlogick <matti@mdranta.net>

vendor/golang.org/x/tools/internal/imports/imports.go

@@ -0,0 +1,388 @@
+// 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"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/format"
+	"go/parser"
+	"go/printer"
+	"go/token"
+	"io"
+	"io/ioutil"
+	"log"
+	"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)
+}
+
+// ApplyFix will apply all of the fixes to the file and format it.
+func ApplyFixes(fixes []*ImportFix, 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
+	}
+
+	// Apply the fixes to the file.
+	apply(fileSet, file, fixes)
+
+	return formatFile(fileSet, file, src, adjust, opt)
+}
+
+// GetAllCandidates gets all of the standard library candidate packages to import in
+// sorted order on import path.
+func GetAllCandidates(filename string, opt *Options) (pkgs []ImportFix, err error) {
+	_, opt, err = initialize(filename, []byte{}, opt)
+	if err != nil {
+		return nil, err
+	}
+	return getAllCandidates(filename, 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,
+		}
+	}
+
+	// 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
+}

vendor/golang.org/x/tools/internal/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 imports
+
+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
+}

vendor/golang.org/x/tools/internal/imports/mkstdlib.go

@@ -0,0 +1,132 @@
+// +build ignore
+
+// mkstdlib generates the zstdlib.go file, containing the Go standard
+// library API symbols. It's baked into the binary to avoid scanning
+// GOPATH in the common case.
+package imports
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/format"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"sort"
+	"strings"
+)
+
+func mustOpen(name string) io.Reader {
+	f, err := os.Open(name)
+	if err != nil {
+		log.Fatal(err)
+	}
+	return f
+}
+
+func api(base string) string {
+	return filepath.Join(runtime.GOROOT(), "api", base)
+}
+
+var sym = regexp.MustCompile(`^pkg (\S+).*?, (?:var|func|type|const) ([A-Z]\w*)`)
+
+var unsafeSyms = map[string]bool{"Alignof": true, "ArbitraryType": true, "Offsetof": true, "Pointer": true, "Sizeof": true}
+
+func main() {
+	var buf bytes.Buffer
+	outf := func(format string, args ...interface{}) {
+		fmt.Fprintf(&buf, format, args...)
+	}
+	outf("// Code generated by mkstdlib.go. DO NOT EDIT.\n\n")
+	outf("package imports\n")
+	outf("var stdlib = map[string]map[string]bool{\n")
+	f := io.MultiReader(
+		mustOpen(api("go1.txt")),
+		mustOpen(api("go1.1.txt")),
+		mustOpen(api("go1.2.txt")),
+		mustOpen(api("go1.3.txt")),
+		mustOpen(api("go1.4.txt")),
+		mustOpen(api("go1.5.txt")),
+		mustOpen(api("go1.6.txt")),
+		mustOpen(api("go1.7.txt")),
+		mustOpen(api("go1.8.txt")),
+		mustOpen(api("go1.9.txt")),
+		mustOpen(api("go1.10.txt")),
+		mustOpen(api("go1.11.txt")),
+		mustOpen(api("go1.12.txt")),
+
+		// The API of the syscall/js package needs to be computed explicitly,
+		// because it's not included in the GOROOT/api/go1.*.txt files at this time.
+		syscallJSAPI(),
+	)
+	sc := bufio.NewScanner(f)
+
+	pkgs := map[string]map[string]bool{
+		"unsafe": unsafeSyms,
+	}
+	paths := []string{"unsafe"}
+
+	for sc.Scan() {
+		l := sc.Text()
+		has := func(v string) bool { return strings.Contains(l, v) }
+		if has("struct, ") || has("interface, ") || has(", method (") {
+			continue
+		}
+		if m := sym.FindStringSubmatch(l); m != nil {
+			path, sym := m[1], m[2]
+
+			if _, ok := pkgs[path]; !ok {
+				pkgs[path] = map[string]bool{}
+				paths = append(paths, path)
+			}
+			pkgs[path][sym] = true
+		}
+	}
+	if err := sc.Err(); err != nil {
+		log.Fatal(err)
+	}
+	sort.Strings(paths)
+	for _, path := range paths {
+		outf("\t%q: map[string]bool{\n", path)
+		pkg := pkgs[path]
+		var syms []string
+		for sym := range pkg {
+			syms = append(syms, sym)
+		}
+		sort.Strings(syms)
+		for _, sym := range syms {
+			outf("\t\t%q: true,\n", sym)
+		}
+		outf("},\n")
+	}
+	outf("}\n")
+	fmtbuf, err := format.Source(buf.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = ioutil.WriteFile("zstdlib.go", fmtbuf, 0666)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+// syscallJSAPI returns the API of the syscall/js package.
+// It's computed from the contents of $(go env GOROOT)/src/syscall/js.
+func syscallJSAPI() io.Reader {
+	var exeSuffix string
+	if runtime.GOOS == "windows" {
+		exeSuffix = ".exe"
+	}
+	cmd := exec.Command("go"+exeSuffix, "run", "cmd/api", "-contexts", "js-wasm", "syscall/js")
+	out, err := cmd.Output()
+	if err != nil {
+		log.Fatalln(err)
+	}
+	return bytes.NewReader(out)
+}

vendor/golang.org/x/tools/internal/imports/mod.go

@@ -0,0 +1,480 @@
+package imports
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/tools/internal/gopathwalk"
+	"golang.org/x/tools/internal/module"
+)
+
+// ModuleResolver implements resolver for modules using the go command as little
+// as feasible.
+type ModuleResolver struct {
+	env            *ProcessEnv
+	moduleCacheDir string
+
+	Initialized   bool
+	Main          *ModuleJSON
+	ModsByModPath []*ModuleJSON // All modules, ordered by # of path components in module Path...
+	ModsByDir     []*ModuleJSON // ...or Dir.
+
+	// moduleCacheInfo stores information about the module cache.
+	moduleCacheInfo *moduleCacheInfo
+}
+
+type ModuleJSON struct {
+	Path     string           // module path
+	Version  string           // module version
+	Versions []string         // available module versions (with -versions)
+	Replace  *ModuleJSON      // replaced by this module
+	Time     *time.Time       // time version was created
+	Update   *ModuleJSON      // available update, if any (with -u)
+	Main     bool             // is this the main module?
+	Indirect bool             // is this module only an indirect dependency of main module?
+	Dir      string           // directory holding files for this module, if any
+	GoMod    string           // path to go.mod file for this module, if any
+	Error    *ModuleErrorJSON // error loading module
+}
+
+type ModuleErrorJSON struct {
+	Err string // the error itself
+}
+
+func (r *ModuleResolver) init() error {
+	if r.Initialized {
+		return nil
+	}
+	stdout, err := r.env.invokeGo("list", "-m", "-json", "...")
+	if err != nil {
+		return err
+	}
+	for dec := json.NewDecoder(stdout); dec.More(); {
+		mod := &ModuleJSON{}
+		if err := dec.Decode(mod); err != nil {
+			return err
+		}
+		if mod.Dir == "" {
+			if r.env.Debug {
+				r.env.Logf("module %v has not been downloaded and will be ignored", mod.Path)
+			}
+			// Can't do anything with a module that's not downloaded.
+			continue
+		}
+		r.ModsByModPath = append(r.ModsByModPath, mod)
+		r.ModsByDir = append(r.ModsByDir, mod)
+		if mod.Main {
+			r.Main = mod
+		}
+	}
+
+	sort.Slice(r.ModsByModPath, func(i, j int) bool {
+		count := func(x int) int {
+			return strings.Count(r.ModsByModPath[x].Path, "/")
+		}
+		return count(j) < count(i) // descending order
+	})
+	sort.Slice(r.ModsByDir, func(i, j int) bool {
+		count := func(x int) int {
+			return strings.Count(r.ModsByDir[x].Dir, "/")
+		}
+		return count(j) < count(i) // descending order
+	})
+
+	if r.moduleCacheInfo == nil {
+		r.moduleCacheInfo = &moduleCacheInfo{
+			modCacheDirInfo: make(map[string]*directoryPackageInfo),
+		}
+	}
+
+	r.Initialized = true
+	return nil
+}
+
+// findPackage returns the module and directory that contains the package at
+// the given import path, or returns nil, "" if no module is in scope.
+func (r *ModuleResolver) findPackage(importPath string) (*ModuleJSON, string) {
+	for _, m := range r.ModsByModPath {
+		if !strings.HasPrefix(importPath, m.Path) {
+			continue
+		}
+		pathInModule := importPath[len(m.Path):]
+		pkgDir := filepath.Join(m.Dir, pathInModule)
+		if r.dirIsNestedModule(pkgDir, m) {
+			continue
+		}
+
+		if info, ok := r.moduleCacheInfo.Load(pkgDir); ok {
+			if packageScanned, err := info.reachedStatus(directoryScanned); packageScanned {
+				if err != nil {
+					// There was some error with scanning this directory.
+					// It does not contain a valid package.
+					continue
+				}
+				return m, pkgDir
+			}
+		}
+
+		pkgFiles, err := ioutil.ReadDir(pkgDir)
+		if err != nil {
+			continue
+		}
+
+		// A module only contains a package if it has buildable go
+		// files in that directory. If not, it could be provided by an
+		// outer module. See #29736.
+		for _, fi := range pkgFiles {
+			if ok, _ := r.env.buildContext().MatchFile(pkgDir, fi.Name()); ok {
+				return m, pkgDir
+			}
+		}
+	}
+	return nil, ""
+}
+
+// findModuleByDir returns the module that contains dir, or nil if no such
+// module is in scope.
+func (r *ModuleResolver) findModuleByDir(dir string) *ModuleJSON {
+	// This is quite tricky and may not be correct. dir could be:
+	// - a package in the main module.
+	// - a replace target underneath the main module's directory.
+	//    - a nested module in the above.
+	// - a replace target somewhere totally random.
+	//    - a nested module in the above.
+	// - in the mod cache.
+	// - in /vendor/ in -mod=vendor mode.
+	//    - nested module? Dunno.
+	// Rumor has it that replace targets cannot contain other replace targets.
+	for _, m := range r.ModsByDir {
+		if !strings.HasPrefix(dir, m.Dir) {
+			continue
+		}
+
+		if r.dirIsNestedModule(dir, m) {
+			continue
+		}
+
+		return m
+	}
+	return nil
+}
+
+// dirIsNestedModule reports if dir is contained in a nested module underneath
+// mod, not actually in mod.
+func (r *ModuleResolver) dirIsNestedModule(dir string, mod *ModuleJSON) bool {
+	if !strings.HasPrefix(dir, mod.Dir) {
+		return false
+	}
+	if r.dirInModuleCache(dir) {
+		// Nested modules in the module cache are pruned,
+		// so it cannot be a nested module.
+		return false
+	}
+	mf := r.findModFile(dir)
+	if mf == "" {
+		return false
+	}
+	return filepath.Dir(mf) != mod.Dir
+}
+
+func (r *ModuleResolver) findModFile(dir string) string {
+	if r.dirInModuleCache(dir) {
+		matches := modCacheRegexp.FindStringSubmatch(dir)
+		index := strings.Index(dir, matches[1]+"@"+matches[2])
+		return filepath.Join(dir[:index], matches[1]+"@"+matches[2], "go.mod")
+	}
+	for {
+		f := filepath.Join(dir, "go.mod")
+		info, err := os.Stat(f)
+		if err == nil && !info.IsDir() {
+			return f
+		}
+		d := filepath.Dir(dir)
+		if len(d) >= len(dir) {
+			return "" // reached top of file system, no go.mod
+		}
+		dir = d
+	}
+}
+
+func (r *ModuleResolver) dirInModuleCache(dir string) bool {
+	if r.moduleCacheDir == "" {
+		return false
+	}
+	return strings.HasPrefix(dir, r.moduleCacheDir)
+}
+
+func (r *ModuleResolver) loadPackageNames(importPaths []string, srcDir string) (map[string]string, error) {
+	if err := r.init(); err != nil {
+		return nil, err
+	}
+	names := map[string]string{}
+	for _, path := range importPaths {
+		_, packageDir := r.findPackage(path)
+		if packageDir == "" {
+			continue
+		}
+		name, err := packageDirToName(packageDir)
+		if err != nil {
+			continue
+		}
+		names[path] = name
+	}
+	return names, nil
+}
+
+func (r *ModuleResolver) scan(_ references) ([]*pkg, error) {
+	if err := r.init(); err != nil {
+		return nil, err
+	}
+
+	// Walk GOROOT, GOPATH/pkg/mod, and the main module.
+	roots := []gopathwalk.Root{
+		{filepath.Join(r.env.GOROOT, "/src"), gopathwalk.RootGOROOT},
+	}
+	if r.Main != nil {
+		roots = append(roots, gopathwalk.Root{r.Main.Dir, gopathwalk.RootCurrentModule})
+	}
+	if r.moduleCacheDir == "" {
+		r.moduleCacheDir = filepath.Join(filepath.SplitList(r.env.GOPATH)[0], "/pkg/mod")
+	}
+	roots = append(roots, gopathwalk.Root{r.moduleCacheDir, gopathwalk.RootModuleCache})
+
+	// Walk replace targets, just in case they're not in any of the above.
+	for _, mod := range r.ModsByModPath {
+		if mod.Replace != nil {
+			roots = append(roots, gopathwalk.Root{mod.Dir, gopathwalk.RootOther})
+		}
+	}
+
+	var result []*pkg
+	dupCheck := make(map[string]bool)
+	var mu sync.Mutex
+
+	// Packages in the module cache are immutable. If we have
+	// already seen this package on a previous scan of the module
+	// cache, return that result.
+	skip := func(root gopathwalk.Root, dir string) bool {
+		mu.Lock()
+		defer mu.Unlock()
+		// If we have already processed this directory on this walk, skip it.
+		if _, dup := dupCheck[dir]; dup {
+			return true
+		}
+
+		// If we have saved this directory information, skip it.
+		info, ok := r.moduleCacheInfo.Load(dir)
+		if !ok {
+			return false
+		}
+		// This directory can be skipped as long as we have already scanned it.
+		// Packages with errors will continue to have errors, so there is no need
+		// to rescan them.
+		packageScanned, _ := info.reachedStatus(directoryScanned)
+		return packageScanned
+	}
+
+	add := func(root gopathwalk.Root, dir string) {
+		mu.Lock()
+		defer mu.Unlock()
+		if _, dup := dupCheck[dir]; dup {
+			return
+		}
+
+		info, err := r.scanDirForPackage(root, dir)
+		if err != nil {
+			return
+		}
+		if root.Type == gopathwalk.RootModuleCache {
+			// Save this package information in the cache and return.
+			// Packages from the module cache are added after Walk.
+			r.moduleCacheInfo.Store(dir, info)
+			return
+		}
+
+		// Skip this package if there was an error loading package info.
+		if info.err != nil {
+			return
+		}
+
+		// The rest of this function canonicalizes the packages using the results
+		// of initializing the resolver from 'go list -m'.
+		res, err := r.canonicalize(info.nonCanonicalImportPath, info.dir, info.needsReplace)
+		if err != nil {
+			return
+		}
+
+		result = append(result, res)
+	}
+
+	gopathwalk.WalkSkip(roots, add, skip, gopathwalk.Options{Debug: r.env.Debug, ModulesEnabled: true})
+
+	// Add the packages from the modules in the mod cache that were skipped.
+	for _, dir := range r.moduleCacheInfo.Keys() {
+		info, ok := r.moduleCacheInfo.Load(dir)
+		if !ok {
+			continue
+		}
+
+		// Skip this directory if we were not able to get the package information successfully.
+		if scanned, err := info.reachedStatus(directoryScanned); !scanned || err != nil {
+			continue
+		}
+
+		res, err := r.canonicalize(info.nonCanonicalImportPath, info.dir, info.needsReplace)
+		if err != nil {
+			continue
+		}
+		result = append(result, res)
+	}
+
+	return result, nil
+}
+
+// canonicalize gets the result of canonicalizing the packages using the results
+// of initializing the resolver from 'go list -m'.
+func (r *ModuleResolver) canonicalize(importPath, dir string, needsReplace bool) (res *pkg, err error) {
+	// Check if the directory is underneath a module that's in scope.
+	if mod := r.findModuleByDir(dir); mod != nil {
+		// It is. If dir is the target of a replace directive,
+		// our guessed import path is wrong. Use the real one.
+		if mod.Dir == dir {
+			importPath = mod.Path
+		} else {
+			dirInMod := dir[len(mod.Dir)+len("/"):]
+			importPath = path.Join(mod.Path, filepath.ToSlash(dirInMod))
+		}
+	} else if needsReplace {
+		return nil, fmt.Errorf("needed this package to be in scope: %s", dir)
+	}
+
+	// We may have discovered a package that has a different version
+	// in scope already. Canonicalize to that one if possible.
+	if _, canonicalDir := r.findPackage(importPath); canonicalDir != "" {
+		dir = canonicalDir
+	}
+	return &pkg{
+		importPathShort: VendorlessPath(importPath),
+		dir:             dir,
+	}, nil
+}
+
+func (r *ModuleResolver) loadExports(ctx context.Context, expectPackage string, pkg *pkg) (map[string]bool, error) {
+	if err := r.init(); err != nil {
+		return nil, err
+	}
+	return loadExportsFromFiles(ctx, r.env, expectPackage, pkg.dir)
+}
+
+func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) (directoryPackageInfo, error) {
+	subdir := ""
+	if dir != root.Path {
+		subdir = dir[len(root.Path)+len("/"):]
+	}
+	importPath := filepath.ToSlash(subdir)
+	if strings.HasPrefix(importPath, "vendor/") {
+		// Ignore vendor dirs. If -mod=vendor is on, then things
+		// should mostly just work, but when it's not vendor/
+		// is a mess. There's no easy way to tell if it's on.
+		// We can still find things in the mod cache and
+		// map them into /vendor when -mod=vendor is on.
+		return directoryPackageInfo{}, fmt.Errorf("vendor directory")
+	}
+	switch root.Type {
+	case gopathwalk.RootCurrentModule:
+		importPath = path.Join(r.Main.Path, filepath.ToSlash(subdir))
+	case gopathwalk.RootModuleCache:
+		matches := modCacheRegexp.FindStringSubmatch(subdir)
+		modPath, err := module.DecodePath(filepath.ToSlash(matches[1]))
+		if err != nil {
+			if r.env.Debug {
+				r.env.Logf("decoding module cache path %q: %v", subdir, err)
+			}
+			return directoryPackageInfo{
+				status: directoryScanned,
+				err:    fmt.Errorf("decoding module cache path %q: %v", subdir, err),
+			}, nil
+		}
+		importPath = path.Join(modPath, filepath.ToSlash(matches[3]))
+	case gopathwalk.RootGOROOT:
+		importPath = subdir
+	}
+
+	// Check that this package is not obviously impossible to import.
+	modFile := r.findModFile(dir)
+
+	var needsReplace bool
+	modBytes, err := ioutil.ReadFile(modFile)
+	if err == nil && !strings.HasPrefix(importPath, modulePath(modBytes)) {
+		// The module's declared path does not match
+		// its expected path. It probably needs a
+		// replace directive we don't have.
+		needsReplace = true
+	}
+
+	return directoryPackageInfo{
+		status:                 directoryScanned,
+		dir:                    dir,
+		nonCanonicalImportPath: importPath,
+		needsReplace:           needsReplace,
+	}, nil
+}
+
+// modCacheRegexp splits a path in a module cache into module, module version, and package.
+var modCacheRegexp = regexp.MustCompile(`(.*)@([^/\\]*)(.*)`)
+
+var (
+	slashSlash = []byte("//")
+	moduleStr  = []byte("module")
+)
+
+// modulePath returns the module path from the gomod file text.
+// If it cannot find a module path, it returns an empty string.
+// It is tolerant of unrelated problems in the go.mod file.
+//
+// Copied from cmd/go/internal/modfile.
+func modulePath(mod []byte) string {
+	for len(mod) > 0 {
+		line := mod
+		mod = nil
+		if i := bytes.IndexByte(line, '\n'); i >= 0 {
+			line, mod = line[:i], line[i+1:]
+		}
+		if i := bytes.Index(line, slashSlash); i >= 0 {
+			line = line[:i]
+		}
+		line = bytes.TrimSpace(line)
+		if !bytes.HasPrefix(line, moduleStr) {
+			continue
+		}
+		line = line[len(moduleStr):]
+		n := len(line)
+		line = bytes.TrimSpace(line)
+		if len(line) == n || len(line) == 0 {
+			continue
+		}
+
+		if line[0] == '"' || line[0] == '`' {
+			p, err := strconv.Unquote(string(line))
+			if err != nil {
+				return "" // malformed quoted string or multiline module path
+			}
+			return p
+		}
+
+		return string(line)
+	}
+	return "" // missing module path
+}

vendor/golang.org/x/tools/internal/imports/mod_cache.go

@@ -0,0 +1,121 @@
+package imports
+
+import (
+	"sync"
+)
+
+// ModuleResolver implements Resolver for modules using the go command as little
+// as feasible.
+//
+// To find packages to import, the resolver needs to know about all of the
+// the packages that could be imported. This includes packages that are
+// already in modules that are in (1) the current module, (2) replace targets,
+// and (3) packages in the module cache. Packages in (1) and (2) may change over
+// time, as the client may edit the current module and locally replaced modules.
+// The module cache (which includes all of the packages in (3)) can only
+// ever be added to.
+//
+// The resolver can thus save state about packages in the module cache
+// and guarantee that this will not change over time. To obtain information
+// about new modules added to the module cache, the module cache should be
+// rescanned.
+//
+// It is OK to serve information about modules that have been deleted,
+// as they do still exist.
+// TODO(suzmue): can we share information with the caller about
+// what module needs to be downloaded to import this package?
+
+type directoryPackageStatus int
+
+const (
+	_ directoryPackageStatus = iota
+	directoryScanned
+)
+
+type directoryPackageInfo struct {
+	// status indicates the extent to which this struct has been filled in.
+	status directoryPackageStatus
+	// err is non-nil when there was an error trying to reach status.
+	err error
+
+	// Set when status > directoryScanned.
+
+	// dir is the absolute directory of this package.
+	dir string
+	// nonCanonicalImportPath is the expected import path for this package.
+	// This may not be an import path that can be used to import this package.
+	nonCanonicalImportPath string
+	// needsReplace is true if the nonCanonicalImportPath does not match the
+	// the modules declared path, making it impossible to import without a
+	// replace directive.
+	needsReplace bool
+}
+
+// reachedStatus returns true when info has a status at least target and any error associated with
+// an attempt to reach target.
+func (info *directoryPackageInfo) reachedStatus(target directoryPackageStatus) (bool, error) {
+	if info.err == nil {
+		return info.status >= target, nil
+	}
+	if info.status == target {
+		return true, info.err
+	}
+	return true, nil
+}
+
+// moduleCacheInfo is a concurrency safe map for storing information about
+// the directories in the module cache.
+//
+// The information in this cache is built incrementally. Entries are initialized in scan.
+// No new keys should be added in any other functions, as all directories containing
+// packages are identified in scan.
+//
+// Other functions, including loadExports and findPackage, may update entries in this cache
+// as they discover new things about the directory.
+//
+// We do not need to protect the data in the cache for multiple writes, because it only stores
+// module cache directories, which do not change. If two competing stores take place, there will be
+// one store that wins. Although this could result in a loss of information it will not be incorrect
+// and may just result in recomputing the same result later.
+//
+// TODO(suzmue): consider other concurrency strategies and data structures (RWLocks, sync.Map, etc)
+type moduleCacheInfo struct {
+	mu sync.Mutex
+	// modCacheDirInfo stores information about packages in
+	// module cache directories. Keyed by absolute directory.
+	modCacheDirInfo map[string]*directoryPackageInfo
+}
+
+// Store stores the package info for dir.
+func (d *moduleCacheInfo) Store(dir string, info directoryPackageInfo) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	d.modCacheDirInfo[dir] = &directoryPackageInfo{
+		status:                 info.status,
+		err:                    info.err,
+		dir:                    info.dir,
+		nonCanonicalImportPath: info.nonCanonicalImportPath,
+		needsReplace:           info.needsReplace,
+	}
+}
+
+// Load returns a copy of the directoryPackageInfo for absolute directory dir.
+func (d *moduleCacheInfo) Load(dir string) (directoryPackageInfo, bool) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	info, ok := d.modCacheDirInfo[dir]
+	if !ok {
+		return directoryPackageInfo{}, false
+	}
+	return *info, true
+}
+
+// Keys returns the keys currently present in d.
+func (d *moduleCacheInfo) Keys() (keys []string) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	for key := range d.modCacheDirInfo {
+		keys = append(keys, key)
+	}
+	return keys
+}

vendor/golang.org/x/tools/internal/imports/sortimports.go

@@ -0,0 +1,280 @@
+// 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(env *ProcessEnv, 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(env, fset, f, d.Specs[i:j])...)
+				i = j
+			}
+		}
+		specs = append(specs, sortSpecs(env, 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)
+			}
+		}
+	}
+}
+
+// mergeImports merges all the import declarations into the first one.
+// Taken from golang.org/x/tools/ast/astutil.
+func mergeImports(env *ProcessEnv, fset *token.FileSet, f *ast.File) {
+	if len(f.Decls) <= 1 {
+		return
+	}
+
+	// Merge all the import declarations into the first one.
+	var first *ast.GenDecl
+	for i := 0; i < len(f.Decls); i++ {
+		decl := f.Decls[i]
+		gen, ok := decl.(*ast.GenDecl)
+		if !ok || gen.Tok != token.IMPORT || declImports(gen, "C") {
+			continue
+		}
+		if first == nil {
+			first = gen
+			continue // Don't touch the first one.
+		}
+		// We now know there is more than one package in this import
+		// declaration. Ensure that it ends up parenthesized.
+		first.Lparen = first.Pos()
+		// Move the imports of the other import declaration to the first one.
+		for _, spec := range gen.Specs {
+			spec.(*ast.ImportSpec).Path.ValuePos = first.Pos()
+			first.Specs = append(first.Specs, spec)
+		}
+		f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
+		i--
+	}
+}
+
+// declImports reports whether gen contains an import of path.
+// Taken from golang.org/x/tools/ast/astutil.
+func declImports(gen *ast.GenDecl, path string) bool {
+	if gen.Tok != token.IMPORT {
+		return false
+	}
+	for _, spec := range gen.Specs {
+		impspec := spec.(*ast.ImportSpec)
+		if importPath(impspec) == path {
+			return true
+		}
+	}
+	return false
+}
+
+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(env *ProcessEnv, 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{env, 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
+		nextSpecPos := pos[i].End
+
+		for _, g := range importComment[s] {
+			for _, c := range g.List {
+				c.Slash = pos[i].End
+				nextSpecPos = c.End()
+			}
+		}
+		if i < len(specs)-1 {
+			pos[i+1].Start = nextSpecPos
+			pos[i+1].End = nextSpecPos
+		}
+	}
+
+	sort.Sort(byCommentPos(comments))
+
+	// Fixup comments can insert blank lines, because import specs are on different lines.
+	// We remove those blank lines here by merging import spec to the first import spec line.
+	firstSpecLine := fset.Position(specs[0].Pos()).Line
+	for _, s := range specs[1:] {
+		p := s.Pos()
+		line := fset.File(p).Line(p)
+		for previousLine := line - 1; previousLine >= firstSpecLine; {
+			fset.File(p).MergeLine(previousLine)
+			previousLine--
+		}
+	}
+	return specs
+}
+
+type byImportSpec struct {
+	env   *ProcessEnv
+	specs []ast.Spec // slice of *ast.ImportSpec
+}
+
+func (x byImportSpec) Len() int      { return len(x.specs) }
+func (x byImportSpec) Swap(i, j int) { x.specs[i], x.specs[j] = x.specs[j], x.specs[i] }
+func (x byImportSpec) Less(i, j int) bool {
+	ipath := importPath(x.specs[i])
+	jpath := importPath(x.specs[j])
+
+	igroup := importGroup(x.env, ipath)
+	jgroup := importGroup(x.env, jpath)
+	if igroup != jgroup {
+		return igroup < jgroup
+	}
+
+	if ipath != jpath {
+		return ipath < jpath
+	}
+	iname := importName(x.specs[i])
+	jname := importName(x.specs[j])
+
+	if iname != jname {
+		return iname < jname
+	}
+	return importComment(x.specs[i]) < importComment(x.specs[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() }