blob: 2d7a23dd3212d48b7f4ad9c74b7eb1cd46108cb5 [file] [log] [blame]
// Copyright 2020 The LUCI Authors.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// Package fmt implements 'fmt' subcommand.
package fmt
import (
// Cmd is 'fmt' subcommand.
func Cmd(params base.Parameters) *subcommands.Command {
return &subcommands.Command{
UsageLine: "fmt [options] [files...]",
ShortDesc: "applies standard formatting to *.star files",
LongDesc: `Applies standard formatting to the given Starlark files.
Accepts zero or more paths via positional arguments, where each path is
either a file or a directory. Directories will be searched for *.star files
recursively. If no positional arguments are given, processes *.star files
recursively starting from the current directory.
By default reformats and rewrites improperly formatted files. Pass -dry-run flag
to just check formatting without overwriting files.
CommandRun: func() subcommands.CommandRun {
fr := &fmtRun{}
fr.Flags.BoolVar(&fr.dryRun, "dry-run", false,
"If set, just check the formatting without rewriting files and "+
"return non-zero exit code if some files need to be formatted")
return fr
type fmtRun struct {
dryRun bool
type fmtResult struct {
// Good is a list of already formatted files.
Good []string `json:"good,omitempty"`
// Unformatted is a list of files that still need formatting.
Unformatted []string `json:"unformatted,omitempty"`
// Formatted is a list of files formatted during this run.
Formatted []string `json:"formatted,omitempty"`
// Failed is a list of files that failed to be formatted.
Failed []string `json:"failed,omitempty"`
func (fr *fmtRun) Run(a subcommands.Application, args []string, env subcommands.Env) int {
if !fr.CheckArgs(args, 0, -1) {
return 1
ctx := cli.GetContext(a, fr, env)
return fr.Done(, args))
func (fr *fmtRun) run(ctx context.Context, inputs []string) (*fmtResult, error) {
files, err := base.ExpandDirectories(inputs)
if err != nil {
return nil, err
l := sync.Mutex{}
outcomes := make(map[string]string, len(files))
const (
outcomeGood = "good"
outcomeUnformatted = "needs formatting"
outcomeFormatted = "formatted"
outcomeFailed = "failure"
outcome := func(path, val string, err error) {
outcomes[path] = val
switch {
case val == outcomeFailed:
fmt.Fprintf(os.Stderr, "%s: %s\n", path, err)
case val != outcomeGood:
fmt.Fprintf(os.Stderr, "%s: %s\n", path, val)
errs := buildifier.Visit(base.PathLoader, files, func(path string, body []byte, f *build.File) errors.MultiError {
formatted := build.Format(f)
if bytes.Equal(body, formatted) {
outcome(path, outcomeGood, nil)
return nil
if fr.dryRun {
outcome(path, outcomeUnformatted, nil)
return nil
if err := ioutil.WriteFile(path, formatted, 0666); err != nil {
outcome(path, outcomeFailed, err)
return errors.NewMultiError(err)
outcome(path, outcomeFormatted, nil)
return nil
// Preserve the order of files in the output.
res := fmtResult{}
for _, p := range files {
switch outcome := outcomes[p]; outcome {
case outcomeGood:
res.Good = append(res.Good, p)
case outcomeUnformatted:
res.Unformatted = append(res.Unformatted, p)
case outcomeFormatted:
res.Formatted = append(res.Formatted, p)
case outcomeFailed, "":
res.Failed = append(res.Failed, p)
res.Unformatted = append(res.Unformatted, p) // still need to format it
if outcome == "" {
fmt.Fprintf(os.Stderr, "%s: skipped due to parsing error\n", p)
if len(res.Unformatted) > 0 { // only happens in dry run
errs = append(errs, fmt.Errorf("Some files need formatting"))
if len(errs) != 0 {
return &res, errs
return &res, nil