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// Copyright 2015 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.
// The fiximports command fixes import declarations to use the canonical
// import path for packages that have an "import comment" as defined by
// https://golang.org/s/go14customimport.
//
//
// Background
//
// The Go 1 custom import path mechanism lets the maintainer of a
// package give it a stable name by which clients may import and "go
// get" it, independent of the underlying version control system (such
// as Git) or server (such as github.com) that hosts it. Requests for
// the custom name are redirected to the underlying name. This allows
// packages to be migrated from one underlying server or system to
// another without breaking existing clients.
//
// Because this redirect mechanism creates aliases for existing
// packages, it's possible for a single program to import the same
// package by its canonical name and by an alias. The resulting
// executable will contain two copies of the package, which is wasteful
// at best and incorrect at worst.
//
// To avoid this, "go build" reports an error if it encounters a special
// comment like the one below, and if the import path in the comment
// does not match the path of the enclosing package relative to
// GOPATH/src:
//
// $ grep ^package $GOPATH/src/github.com/bob/vanity/foo/foo.go
// package foo // import "vanity.com/foo"
//
// The error from "go build" indicates that the package canonically
// known as "vanity.com/foo" is locally installed under the
// non-canonical name "github.com/bob/vanity/foo".
//
//
// Usage
//
// When a package that you depend on introduces a custom import comment,
// and your workspace imports it by the non-canonical name, your build
// will stop working as soon as you update your copy of that package
// using "go get -u".
//
// The purpose of the fiximports tool is to fix up all imports of the
// non-canonical path within a Go workspace, replacing them with imports
// of the canonical path. Following a run of fiximports, the workspace
// will no longer depend on the non-canonical copy of the package, so it
// should be safe to delete. It may be necessary to run "go get -u"
// again to ensure that the package is locally installed under its
// canonical path, if it was not already.
//
// The fiximports tool operates locally; it does not make HTTP requests
// and does not discover new custom import comments. It only operates
// on non-canonical packages present in your workspace.
//
// The -baddomains flag is a list of domain names that should always be
// considered non-canonical. You can use this if you wish to make sure
// that you no longer have any dependencies on packages from that
// domain, even those that do not yet provide a canonical import path
// comment. For example, the default value of -baddomains includes the
// moribund code hosting site code.google.com, so fiximports will report
// an error for each import of a package from this domain remaining
// after canonicalization.
//
// To see the changes fiximports would make without applying them, use
// the -n flag.
//
package main
import (
"bytes"
"encoding/json"
"flag"
"fmt"
"go/ast"
"go/build"
"go/format"
"go/parser"
"go/token"
"io"
"io/ioutil"
"log"
"os"
"os/exec"
"path"
"path/filepath"
"sort"
"strconv"
"strings"
)
// flags
var (
dryrun = flag.Bool("n", false, "dry run: show changes, but don't apply them")
badDomains = flag.String("baddomains", "code.google.com",
"a comma-separated list of domains from which packages should not be imported")
replaceFlag = flag.String("replace", "",
"a comma-separated list of noncanonical=canonical pairs of package paths. If both items in a pair end with '...', they are treated as path prefixes.")
)
// seams for testing
var (
stderr io.Writer = os.Stderr
writeFile = ioutil.WriteFile
)
const usage = `fiximports: rewrite import paths to use canonical package names.
Usage: fiximports [-n] package...
The package... arguments specify a list of packages
in the style of the go tool; see "go help packages".
Hint: use "all" or "..." to match the entire workspace.
For details, see https://pkg.go.dev/golang.org/x/tools/cmd/fiximports
Flags:
-n: dry run: show changes, but don't apply them
-baddomains a comma-separated list of domains from which packages
should not be imported
`
func main() {
flag.Parse()
if len(flag.Args()) == 0 {
fmt.Fprint(stderr, usage)
os.Exit(1)
}
if !fiximports(flag.Args()...) {
os.Exit(1)
}
}
type canonicalName struct{ path, name string }
// fiximports fixes imports in the specified packages.
// Invariant: a false result implies an error was already printed.
func fiximports(packages ...string) bool {
// importedBy is the transpose of the package import graph.
importedBy := make(map[string]map[*build.Package]bool)
// addEdge adds an edge to the import graph.
addEdge := func(from *build.Package, to string) {
if to == "C" || to == "unsafe" {
return // fake
}
pkgs := importedBy[to]
if pkgs == nil {
pkgs = make(map[*build.Package]bool)
importedBy[to] = pkgs
}
pkgs[from] = true
}
// List metadata for all packages in the workspace.
pkgs, err := list("...")
if err != nil {
fmt.Fprintf(stderr, "importfix: %v\n", err)
return false
}
// packageName maps each package's path to its name.
packageName := make(map[string]string)
for _, p := range pkgs {
packageName[p.ImportPath] = p.Package.Name
}
// canonical maps each non-canonical package path to
// its canonical path and name.
// A present nil value indicates that the canonical package
// is unknown: hosted on a bad domain with no redirect.
canonical := make(map[string]canonicalName)
domains := strings.Split(*badDomains, ",")
type replaceItem struct {
old, new string
matchPrefix bool
}
var replace []replaceItem
for _, pair := range strings.Split(*replaceFlag, ",") {
if pair == "" {
continue
}
words := strings.Split(pair, "=")
if len(words) != 2 {
fmt.Fprintf(stderr, "importfix: -replace: %q is not of the form \"canonical=noncanonical\".\n", pair)
return false
}
replace = append(replace, replaceItem{
old: strings.TrimSuffix(words[0], "..."),
new: strings.TrimSuffix(words[1], "..."),
matchPrefix: strings.HasSuffix(words[0], "...") &&
strings.HasSuffix(words[1], "..."),
})
}
// Find non-canonical packages and populate importedBy graph.
for _, p := range pkgs {
if p.Error != nil {
msg := p.Error.Err
if strings.Contains(msg, "code in directory") &&
strings.Contains(msg, "expects import") {
// don't show the very errors we're trying to fix
} else {
fmt.Fprintln(stderr, p.Error)
}
}
for _, imp := range p.Imports {
addEdge(&p.Package, imp)
}
for _, imp := range p.TestImports {
addEdge(&p.Package, imp)
}
for _, imp := range p.XTestImports {
addEdge(&p.Package, imp)
}
// Does package have an explicit import comment?
if p.ImportComment != "" {
if p.ImportComment != p.ImportPath {
canonical[p.ImportPath] = canonicalName{
path: p.Package.ImportComment,
name: p.Package.Name,
}
}
} else {
// Is package matched by a -replace item?
var newPath string
for _, item := range replace {
if item.matchPrefix {
if strings.HasPrefix(p.ImportPath, item.old) {
newPath = item.new + p.ImportPath[len(item.old):]
break
}
} else if p.ImportPath == item.old {
newPath = item.new
break
}
}
if newPath != "" {
newName := packageName[newPath]
if newName == "" {
newName = filepath.Base(newPath) // a guess
}
canonical[p.ImportPath] = canonicalName{
path: newPath,
name: newName,
}
continue
}
// Is package matched by a -baddomains item?
for _, domain := range domains {
slash := strings.Index(p.ImportPath, "/")
if slash < 0 {
continue // no slash: standard package
}
if p.ImportPath[:slash] == domain {
// Package comes from bad domain and has no import comment.
// Report an error each time this package is imported.
canonical[p.ImportPath] = canonicalName{}
// TODO(adonovan): should we make an HTTP request to
// see if there's an HTTP redirect, a "go-import" meta tag,
// or an import comment in the latest revision?
// It would duplicate a lot of logic from "go get".
}
break
}
}
}
// Find all clients (direct importers) of canonical packages.
// These are the packages that need fixing up.
clients := make(map[*build.Package]bool)
for path := range canonical {
for client := range importedBy[path] {
clients[client] = true
}
}
// Restrict rewrites to the set of packages specified by the user.
if len(packages) == 1 && (packages[0] == "all" || packages[0] == "...") {
// no restriction
} else {
pkgs, err := list(packages...)
if err != nil {
fmt.Fprintf(stderr, "importfix: %v\n", err)
return false
}
seen := make(map[string]bool)
for _, p := range pkgs {
seen[p.ImportPath] = true
}
for client := range clients {
if !seen[client.ImportPath] {
delete(clients, client)
}
}
}
// Rewrite selected client packages.
ok := true
for client := range clients {
if !rewritePackage(client, canonical) {
ok = false
// There were errors.
// Show direct and indirect imports of client.
seen := make(map[string]bool)
var direct, indirect []string
for p := range importedBy[client.ImportPath] {
direct = append(direct, p.ImportPath)
seen[p.ImportPath] = true
}
var visit func(path string)
visit = func(path string) {
for q := range importedBy[path] {
qpath := q.ImportPath
if !seen[qpath] {
seen[qpath] = true
indirect = append(indirect, qpath)
visit(qpath)
}
}
}
if direct != nil {
fmt.Fprintf(stderr, "\timported directly by:\n")
sort.Strings(direct)
for _, path := range direct {
fmt.Fprintf(stderr, "\t\t%s\n", path)
visit(path)
}
if indirect != nil {
fmt.Fprintf(stderr, "\timported indirectly by:\n")
sort.Strings(indirect)
for _, path := range indirect {
fmt.Fprintf(stderr, "\t\t%s\n", path)
}
}
}
}
}
return ok
}
// Invariant: false result => error already printed.
func rewritePackage(client *build.Package, canonical map[string]canonicalName) bool {
ok := true
used := make(map[string]bool)
var filenames []string
filenames = append(filenames, client.GoFiles...)
filenames = append(filenames, client.TestGoFiles...)
filenames = append(filenames, client.XTestGoFiles...)
var first bool
for _, filename := range filenames {
if !first {
first = true
fmt.Fprintf(stderr, "%s\n", client.ImportPath)
}
err := rewriteFile(filepath.Join(client.Dir, filename), canonical, used)
if err != nil {
fmt.Fprintf(stderr, "\tERROR: %v\n", err)
ok = false
}
}
// Show which imports were renamed in this package.
var keys []string
for key := range used {
keys = append(keys, key)
}
sort.Strings(keys)
for _, key := range keys {
if p := canonical[key]; p.path != "" {
fmt.Fprintf(stderr, "\tfixed: %s -> %s\n", key, p.path)
} else {
fmt.Fprintf(stderr, "\tERROR: %s has no import comment\n", key)
ok = false
}
}
return ok
}
// rewrite reads, modifies, and writes filename, replacing all imports
// of packages P in canonical by canonical[P].
// It records in used which canonical packages were imported.
// used[P]=="" indicates that P was imported but its canonical path is unknown.
func rewriteFile(filename string, canonical map[string]canonicalName, used map[string]bool) error {
fset := token.NewFileSet()
f, err := parser.ParseFile(fset, filename, nil, parser.ParseComments)
if err != nil {
return err
}
var changed bool
for _, imp := range f.Imports {
impPath, err := strconv.Unquote(imp.Path.Value)
if err != nil {
log.Printf("%s: bad import spec %q: %v",
fset.Position(imp.Pos()), imp.Path.Value, err)
continue
}
canon, ok := canonical[impPath]
if !ok {
continue // import path is canonical
}
used[impPath] = true
if canon.path == "" {
// The canonical path is unknown (a -baddomain).
// Show the offending import.
// TODO(adonovan): should we show the actual source text?
fmt.Fprintf(stderr, "\t%s:%d: import %q\n",
shortPath(filename),
fset.Position(imp.Pos()).Line, impPath)
continue
}
changed = true
imp.Path.Value = strconv.Quote(canon.path)
// Add a renaming import if necessary.
//
// This is a guess at best. We can't see whether a 'go
// get' of the canonical import path would have the same
// name or not. Assume it's the last segment.
newBase := path.Base(canon.path)
if imp.Name == nil && newBase != canon.name {
imp.Name = &ast.Ident{Name: canon.name}
}
}
if changed && !*dryrun {
var buf bytes.Buffer
if err := format.Node(&buf, fset, f); err != nil {
return fmt.Errorf("%s: couldn't format file: %v", filename, err)
}
return writeFile(filename, buf.Bytes(), 0644)
}
return nil
}
// listPackage is a copy of cmd/go/list.Package.
// It has more fields than build.Package and we need some of them.
type listPackage struct {
build.Package
Error *packageError // error loading package
}
// A packageError describes an error loading information about a package.
type packageError struct {
ImportStack []string // shortest path from package named on command line to this one
Pos string // position of error
Err string // the error itself
}
func (e packageError) Error() string {
if e.Pos != "" {
return e.Pos + ": " + e.Err
}
return e.Err
}
// list runs 'go list' with the specified arguments and returns the
// metadata for matching packages.
func list(args ...string) ([]*listPackage, error) {
cmd := exec.Command("go", append([]string{"list", "-e", "-json"}, args...)...)
cmd.Stdout = new(bytes.Buffer)
cmd.Stderr = stderr
if err := cmd.Run(); err != nil {
return nil, err
}
dec := json.NewDecoder(cmd.Stdout.(io.Reader))
var pkgs []*listPackage
for {
var p listPackage
if err := dec.Decode(&p); err == io.EOF {
break
} else if err != nil {
return nil, err
}
pkgs = append(pkgs, &p)
}
return pkgs, nil
}
// cwd contains the current working directory of the tool.
//
// It is initialized directly so that its value will be set for any other
// package variables or init functions that depend on it, such as the gopath
// variable in main_test.go.
var cwd string = func() string {
cwd, err := os.Getwd()
if err != nil {
log.Fatalf("os.Getwd: %v", err)
}
return cwd
}()
// shortPath returns an absolute or relative name for path, whatever is shorter.
// Plundered from $GOROOT/src/cmd/go/build.go.
func shortPath(path string) string {
if rel, err := filepath.Rel(cwd, path); err == nil && len(rel) < len(path) {
return rel
}
return path
}