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🚫💩 lint-staged

npm version

Run linters against staged git files and don't let :poop: slip into your code base!

npm install --save-dev lint-staged # requires further setup

$ git commit

✔ Backed up original state in git stash (5bda95f)
❯ Running tasks for staged files...
  ❯ packages/frontend/.lintstagedrc.json — 1 file
    ↓ *.js — no files [SKIPPED]
    ❯ *.{json,md} — 1 file
      ⠹ prettier --write
  ↓ packages/backend/.lintstagedrc.json — 2 files
    ❯ *.js — 2 files
      ⠼ eslint --fix
    ↓ *.{json,md} — no files [SKIPPED]
◼ Applying modifications from tasks...
◼ Cleaning up temporary files...
<details> <summary>See asciinema video</summary>

asciicast

</details>

Why

Linting makes more sense when run before committing your code. By doing so you can ensure no errors go into the repository and enforce code style. But running a lint process on a whole project is slow, and linting results can be irrelevant. Ultimately you only want to lint files that will be committed.

This project contains a script that will run arbitrary shell tasks with a list of staged files as an argument, filtered by a specified glob pattern.

Related blog posts and talks

If you've written one, please submit a PR with the link to it!

Installation and setup

To install lint-staged in the recommended way, you need to:

  1. Install lint-staged itself:
    • npm install --save-dev lint-staged
  2. Set up the pre-commit git hook to run lint-staged
    • Husky is a popular choice for configuring git hooks
    • Read more about git hooks here
  3. Install some linters, like ESLint or Prettier
  4. Configure lint-staged to run linters and other tasks:
    • for example: { "*.js": "eslint" } to run ESLint for all staged JS files
    • See Configuration for more info

Don't forget to commit changes to package.json and .husky to share this setup with your team!

Now change a few files, git add or git add --patch some of them to your commit, and try to git commit them.

See examples and configuration for more information.

[!CAUTION]
Lint-staged runs git operations affecting the files in your repository. By default lint-staged creates a git stash as a backup of the original state before running any configured tasks to help prevent data loss.

Changelog

See Releases.

Migration

v15

v14

v13

v12

v10

Command line flags

❯ npx lint-staged --help
Usage: lint-staged [options]

Options:
  -V, --version                      output the version number
  --allow-empty                      allow empty commits when tasks revert all staged changes (default: false)
  -p, --concurrent <number|boolean>  the number of tasks to run concurrently, or false for serial (default: true)
  -c, --config [path]                path to configuration file, or - to read from stdin
  --cwd [path]                       run all tasks in specific directory, instead of the current
  -d, --debug                        print additional debug information (default: false)
  --diff [string]                    override the default "--staged" flag of "git diff" to get list of files.
                                     Implies "--no-stash".
  --diff-filter [string]             override the default "--diff-filter=ACMR" flag of "git diff" to get list of
                                     files
  --max-arg-length [number]          maximum length of the command-line argument string (default: 0)
  --no-stash                         disable the backup stash, and do not revert in case of errors. Implies
                                     "--no-hide-partially-staged".
  --no-hide-partially-staged         disable hiding unstaged changes from partially staged files
  -q, --quiet                        disable lint-staged’s own console output (default: false)
  -r, --relative                     pass relative filepaths to tasks (default: false)
  -x, --shell [path]                 skip parsing of tasks for better shell support (default: false)
  -v, --verbose                      show task output even when tasks succeed; by default only failed output is
                                     shown (default: false)
  -h, --help                         display help for command

Any lost modifications can be restored from a git stash:

  > git stash list
  stash@{0}: automatic lint-staged backup
  > git stash apply --index stash@{0}

Configuration

Lint-staged can be configured in many ways:

Configuration should be an object where each value is a command to run and its key is a glob pattern to use for this command. This package uses micromatch for glob patterns. JavaScript files can also export advanced configuration as a function. See Using JS configuration files for more info.

You can also place multiple configuration files in different directories inside a project. For a given staged file, the closest configuration file will always be used. See "How to use lint-staged in a multi-package monorepo?" for more info and an example.

package.json example:

{
  "lint-staged": {
    "*": "your-cmd"
  }
}

.lintstagedrc example

{
  "*": "your-cmd"
}

This config will execute your-cmd with the list of currently staged files passed as arguments.

So, considering you did git add file1.ext file2.ext, lint-staged will run the following command:

your-cmd file1.ext file2.ext

Task concurrency

By default lint-staged will run configured tasks concurrently. This means that for every glob, all the commands will be started at the same time. With the following config, both eslint and prettier will run at the same time:

{
  "*.ts": "eslint",
  "*.md": "prettier --list-different"
}

This is typically not a problem since the globs do not overlap, and the commands do not make changes to the files, but only report possible errors (aborting the git commit). If you want to run multiple commands for the same set of files, you can use the array syntax to make sure commands are run in order. In the following example, prettier will run for both globs, and in addition eslint will run for *.ts files after it. Both sets of commands (for each glob) are still started at the same time (but do not overlap).

{
  "*.ts": ["prettier --list-different", "eslint"],
  "*.md": "prettier --list-different"
}

Pay extra attention when the configured globs overlap, and tasks make edits to files. For example, in this configuration prettier and eslint might try to make changes to the same *.ts file at the same time, causing a race condition:

{
  "*": "prettier --write",
  "*.ts": "eslint --fix"
}

You can solve it using the negation pattern and the array syntax:

{
  "!(*.ts)": "prettier --write",
  "*.ts": ["eslint --fix", "prettier --write"]
}

Another example in which tasks make edits to files and globs match multiple files but don't overlap:

{
  "*.css": ["stylelint --fix", "prettier --write"],
  "*.{js,jsx}": ["eslint --fix", "prettier --write"],
  "!(*.css|*.js|*.jsx)": ["prettier --write"]
}

Or, if necessary, you can limit the concurrency using --concurrent <number> or disable it entirely with --concurrent false.

Filtering files

Linter commands work on a subset of all staged files, defined by a glob pattern. lint-staged uses micromatch for matching files with the following rules:

When matching, lint-staged will do the following

NOTE: lint-staged will pass absolute paths to the linters to avoid any confusion in case they're executed in a different working directory (i.e. when your .git directory isn't the same as your package.json directory).

Also see How to use lint-staged in a multi-package monorepo?

Ignoring files

The concept of lint-staged is to run configured linter tasks (or other tasks) on files that are staged in git. lint-staged will always pass a list of all staged files to the task, and ignoring any files should be configured in the task itself.

Consider a project that uses prettier to keep code format consistent across all files. The project also stores minified 3rd-party vendor libraries in the vendor/ directory. To keep prettier from throwing errors on these files, the vendor directory should be added to prettier's ignore configuration, the .prettierignore file. Running npx prettier . will ignore the entire vendor directory, throwing no errors. When lint-staged is added to the project and configured to run prettier, all modified and staged files in the vendor directory will be ignored by prettier, even though it receives them as input.

In advanced scenarios, where it is impossible to configure the linter task itself to ignore files, but some staged files should still be ignored by lint-staged, it is possible to filter filepaths before passing them to tasks by using the function syntax. See Example: Ignore files from match.

What commands are supported?

Supported are any executables installed locally or globally via npm as well as any executable from your $PATH.

Using globally installed scripts is discouraged, since lint-staged may not work for someone who doesn't have it installed.

lint-staged uses execa to locate locally installed scripts. So in your .lintstagedrc you can write:

{
  "*.js": "eslint --fix"
}

This will result in lint-staged running eslint --fix file-1.js file-2.js, when you have staged files file-1.js, file-2.js and README.md.

Pass arguments to your commands separated by space as you would do in the shell. See examples below.

Running multiple commands in a sequence

You can run multiple commands in a sequence on every glob. To do so, pass an array of commands instead of a single one. This is useful for running autoformatting tools like eslint --fix or stylefmt but can be used for any arbitrary sequences.

For example:

{
  "*.js": ["eslint", "prettier --write"]
}

going to execute eslint and if it exits with 0 code, it will execute prettier --write on all staged *.js files.

This will result in lint-staged running eslint file-1.js file-2.js, when you have staged files file-1.js, file-2.js and README.md, and if it passes, prettier --write file-1.js file-2.js.

Using JS configuration files

Writing the configuration file in JavaScript is the most powerful way to configure lint-staged (lint-staged.config.js, similar, or passed via --config). From the configuration file, you can export either a single function or an object.

If the exports value is a function, it will receive an array of all staged filenames. You can then build your own matchers for the files and return a command string or an array of command strings. These strings are considered complete and should include the filename arguments, if wanted.

If the exports value is an object, its keys should be glob matches (like in the normal non-js config format). The values can either be like in the normal config or individual functions like described above. Instead of receiving all matched files, the functions in the exported object will only receive the staged files matching the corresponding glob key.

To summarize, by default lint-staged automatically adds the list of matched staged files to your command, but when building the command using JS functions it is expected to do this manually. For example:

export default {
  '*.js': (stagedFiles) => [`eslint .`, `prettier --write ${stagedFiles.join(' ')}`],
}

This will result in lint-staged first running eslint . (matching all files), and if it passes, prettier --write file-1.js file-2.js, when you have staged files file-1.js, file-2.js and README.md.

Function signature

The function can also be async:

(filenames: string[]) => string | string[] | Promise<string | string[]>

Example: Export a function to build your own matchers

<details> <summary>Click to expand</summary> 
// lint-staged.config.js
import micromatch from 'micromatch'

export default (allStagedFiles) => {
  const shFiles = micromatch(allStagedFiles, ['**/src/**/*.sh'])
  if (shFiles.length) {
    return `printf '%s\n' "Script files aren't allowed in src directory" >&2`
  }
  const codeFiles = micromatch(allStagedFiles, ['**/*.js', '**/*.ts'])
  const docFiles = micromatch(allStagedFiles, ['**/*.md'])
  return [`eslint ${codeFiles.join(' ')}`, `mdl ${docFiles.join(' ')}`]
}
</details>

Example: Wrap filenames in single quotes and run once per file

<details> <summary>Click to expand</summary> 
// .lintstagedrc.js
export default {
  '**/*.js?(x)': (filenames) => filenames.map((filename) => `prettier --write '${filename}'`),
}
</details>

Example: Run tsc on changes to TypeScript files, but do not pass any filename arguments

<details> <summary>Click to expand</summary> 
// lint-staged.config.js
export default {
  '**/*.ts?(x)': () => 'tsc -p tsconfig.json --noEmit',
}
</details>

Example: Run ESLint on entire repo if more than 10 staged files

<details> <summary>Click to expand</summary> 
// .lintstagedrc.js
export default {
  '**/*.js?(x)': (filenames) =>
    filenames.length > 10 ? 'eslint .' : `eslint ${filenames.join(' ')}`,
}
</details>

Example: Use your own globs

<details> <summary>Click to expand</summary>

It's better to use the function-based configuration (seen above), if your use case is this.

// lint-staged.config.js
import micromatch from 'micromatch'

export default {
  '*': (allFiles) => {
    const codeFiles = micromatch(allFiles, ['**/*.js', '**/*.ts'])
    const docFiles = micromatch(allFiles, ['**/*.md'])
    return [`eslint ${codeFiles.join(' ')}`, `mdl ${docFiles.join(' ')}`]
  },
}
</details>

Example: Ignore files from match

<details> <summary>Click to expand</summary>

If for some reason you want to ignore files from the glob match, you can use micromatch.not():

// lint-staged.config.js
import micromatch from 'micromatch'

export default {
  '*.js': (files) => {
    // from `files` filter those _NOT_ matching `*test.js`
    const match = micromatch.not(files, '*test.js')
    return `eslint ${match.join(' ')}`
  },
}

Please note that for most cases, globs can achieve the same effect. For the above example, a matching glob would be !(*test).js.

</details>

Example: Use relative paths for commands

<details> <summary>Click to expand</summary> 
import path from 'path'

export default {
  '*.ts': (absolutePaths) => {
    const cwd = process.cwd()
    const relativePaths = absolutePaths.map((file) => path.relative(cwd, file))
    return `ng lint myProjectName --files ${relativePaths.join(' ')}`
  },
}
</details>

Reformatting the code

Tools like Prettier, ESLint/TSLint, or stylelint can reformat your code according to an appropriate config by running prettier --write/eslint --fix/tslint --fix/stylelint --fix. Lint-staged will automatically add any modifications to the commit as long as there are no errors.

{
  "*.js": "prettier --write"
}

Prior to version 10, tasks had to manually include git add as the final step. This behavior has been integrated into lint-staged itself in order to prevent race conditions with multiple tasks editing the same files. If lint-staged detects git add in task configurations, it will show a warning in the console. Please remove git add from your configuration after upgrading.

Examples

All examples assume you've already set up lint-staged in the package.json file and husky in its own config file.

{
  "name": "My project",
  "version": "0.1.0",
  "scripts": {
    "my-custom-script": "linter --arg1 --arg2"
  },
  "lint-staged": {}
}

In .husky/pre-commit

# .husky/pre-commit

npx lint-staged

Note: we don't pass a path as an argument for the runners. This is important since lint-staged will do this for you.

ESLint with default parameters for *.js and *.jsx running as a pre-commit hook

<details> <summary>Click to expand</summary> 
{
  "*.{js,jsx}": "eslint"
}
</details>

Automatically fix code style with --fix and add to commit

<details> <summary>Click to expand</summary> 
{
  "*.js": "eslint --fix"
}

This will run eslint --fix and automatically add changes to the commit.

</details>

Reuse npm script

<details> <summary>Click to expand</summary>

If you wish to reuse a npm script defined in your package.json:

{
  "*.js": "npm run my-custom-script --"
}

The following is equivalent:

{
  "*.js": "linter --arg1 --arg2"
}
</details>

Use environment variables with linting commands

<details> <summary>Click to expand</summary>

Linting commands do not support the shell convention of expanding environment variables. To enable the convention yourself, use a tool like cross-env.

For example, here is jest running on all .js files with the NODE_ENV variable being set to "test":

{
  "*.js": ["cross-env NODE_ENV=test jest --bail --findRelatedTests"]
}
</details>

Automatically fix code style with prettier for any format Prettier supports

<details> <summary>Click to expand</summary> 
{
  "*": "prettier --ignore-unknown --write"
}
</details>

Automatically fix code style with prettier for JavaScript, TypeScript, Markdown, HTML, or CSS

<details> <summary>Click to expand</summary> 
{
  "*.{js,jsx,ts,tsx,md,html,css}": "prettier --write"
}
</details>

Stylelint for CSS with defaults and for SCSS with SCSS syntax

<details> <summary>Click to expand</summary> 
{
  "*.css": "stylelint",
  "*.scss": "stylelint --syntax=scss"
}
</details>

Run PostCSS sorting and Stylelint to check

<details> <summary>Click to expand</summary> 
{
  "*.scss": ["postcss --config path/to/your/config --replace", "stylelint"]
}
</details>

Minify the images

<details> <summary>Click to expand</summary> 
{
  "*.{png,jpeg,jpg,gif,svg}": "imagemin-lint-staged"
}
<details> <summary>More about <code>imagemin-lint-staged</code></summary>

imagemin-lint-staged is a CLI tool designed for lint-staged usage with sensible defaults.

See more on this blog post for benefits of this approach.

</details> </details>

Typecheck your staged files with flow

<details> <summary>Click to expand</summary> 
{
  "*.{js,jsx}": "flow focus-check"
}
</details>

Integrate with Next.js

<details> <summary>Click to expand</summary> 
// .lintstagedrc.js
// See https://nextjs.org/docs/basic-features/eslint#lint-staged for details

const path = require('path')

const buildEslintCommand = (filenames) =>
  `next lint --fix --file ${filenames.map((f) => path.relative(process.cwd(), f)).join(' --file ')}`

module.exports = {
  '*.{js,jsx,ts,tsx}': [buildEslintCommand],
}
</details>

Frequently Asked Questions

The output of commit hook looks weird (no colors, duplicate lines, verbose output on Windows, …)

<details> <summary>Click to expand</summary>

Git 2.36.0 introduced a change to hooks where they were no longer run in the original TTY. This was fixed in 2.37.0:

https://raw.githubusercontent.com/git/git/master/Documentation/RelNotes/2.37.0.txt

If updating Git doesn't help, you can try to manually redirect the output in your Git hook; for example:

# .husky/pre-commit

if sh -c ": >/dev/tty" >/dev/null 2>/dev/null; then exec >/dev/tty 2>&1; fi

npx lint-staged

Source: https://github.com/typicode/husky/issues/968#issuecomment-1176848345

</details>

Can I use lint-staged via node?

<details> <summary>Click to expand</summary>

Yes!

import lintStaged from 'lint-staged'

try {
  const success = await lintStaged()
  console.log(success ? 'Linting was successful!' : 'Linting failed!')
} catch (e) {
  // Failed to load configuration
  console.error(e)
}

Parameters to lintStaged are equivalent to their CLI counterparts:

const success = await lintStaged({
  allowEmpty: false,
  concurrent: true,
  configPath: './path/to/configuration/file',
  cwd: process.cwd(),
  debug: false,
  maxArgLength: null,
  quiet: false,
  relative: false,
  shell: false,
  stash: true,
  verbose: false,
})

You can also pass config directly with config option:

const success = await lintStaged({
  allowEmpty: false,
  concurrent: true,
  config: { '*.js': 'eslint --fix' },
  cwd: process.cwd(),
  debug: false,
  maxArgLength: null,
  quiet: false,
  relative: false,
  shell: false,
  stash: true,
  verbose: false,
})

The maxArgLength option configures chunking of tasks into multiple parts that are run one after the other. This is to avoid issues on Windows platforms where the maximum length of the command line argument string is limited to 8192 characters. Lint-staged might generate a very long argument string when there are many staged files. This option is set automatically from the cli, but not via the Node.js API by default.

</details>

Using with JetBrains IDEs (WebStorm, PyCharm, IntelliJ IDEA, RubyMine, etc.)

<details> <summary>Click to expand</summary>

Update: The latest version of JetBrains IDEs now support running hooks as you would expect.

When using the IDE's GUI to commit changes with the precommit hook, you might see inconsistencies in the IDE and command line. This is known issue at JetBrains so if you want this fixed, please vote for it on YouTrack.

Until the issue is resolved in the IDE, you can use the following config to work around it:

husky v1.x

{
  "husky": {
    "hooks": {
      "pre-commit": "lint-staged",
      "post-commit": "git update-index --again"
    }
  }
}

husky v0.x

{
  "scripts": {
    "precommit": "lint-staged",
    "postcommit": "git update-index --again"
  }
}

Thanks to this comment for the fix!

</details>

How to use lint-staged in a multi-package monorepo?

<details> <summary>Click to expand</summary>

Install lint-staged on the monorepo root level, and add separate configuration files in each package. When running, lint-staged will always use the configuration closest to a staged file, so having separate configuration files makes sure linters do not "leak" into other packages.

For example, in a monorepo with packages/frontend/.lintstagedrc.json and packages/backend/.lintstagedrc.json, a staged file inside packages/frontend/ will only match that configuration, and not the one in packages/backend/.

Note: lint-staged discovers the closest configuration to each staged file, even if that configuration doesn't include any matching globs. Given these example configurations:

// ./.lintstagedrc.json
{ "*.md": "prettier --write" }

// ./packages/frontend/.lintstagedrc.json
{ "*.js": "eslint --fix" }

When committing ./packages/frontend/README.md, it will not run prettier, because the configuration in the frontend/ directory is closer to the file and doesn't include it. You should treat all lint-staged configuration files as isolated and separated from each other. You can always use JS files to "extend" configurations, for example:

import baseConfig from '../.lintstagedrc.js'

export default {
  ...baseConfig,
  '*.js': 'eslint --fix',
}

To support backwards-compatibility, monorepo features require multiple lint-staged configuration files present in the git repo. If you still want to run lint-staged in only one of the packages in a monorepo, you can either add an "empty" lint-staged configuration to the root of the repo (so that there's two configs in total), or alternatively run lint-staged with the --cwd option pointing to your package directory (for example, lint-staged --cwd packages/frontend).

</details>

Can I lint files outside of the current project folder?

<details> <summary>Click to expand</summary>

tl;dr: Yes, but the pattern should start with ../.

By default, lint-staged executes linters only on the files present inside the project folder(where lint-staged is installed and run from). So this question is relevant only when the project folder is a child folder inside the git repo. In certain project setups, it might be desirable to bypass this restriction. See #425, #487 for more context.

lint-staged provides an escape hatch for the same(>= v7.3.0). For patterns that start with ../, all the staged files are allowed to match against the pattern. Note that patterns like *.js, **/*.js will still only match the project files and not any of the files in parent or sibling directories.

Example repo: sudo-suhas/lint-staged-django-react-demo.

</details>

Can I run lint-staged in CI, or when there are no staged files?

<details> <summary>Click to expand</summary>

Lint-staged will by default run against files staged in git, and should be run during the git pre-commit hook, for example. It's also possible to override this default behaviour and run against files in a specific diff, for example all changed files between two different branches. If you want to run lint-staged in the CI, maybe you can set it up to compare the branch in a Pull Request/Merge Request to the target branch.

Try out the git diff command until you are satisfied with the result, for example:

git diff --diff-filter=ACMR --name-only master...my-branch

This will print a list of added, changed, modified, and renamed files between master and my-branch.

You can then run lint-staged against the same files with:

npx lint-staged --diff="master...my-branch"
</details>

Can I use lint-staged with ng lint

<details> <summary>Click to expand</summary>

You should not use ng lint through lint-staged, because it's designed to lint an entire project. Instead, you can add ng lint to your git pre-commit hook the same way as you would run lint-staged.

See issue !951 for more details and possible workarounds.

</details>

How can I ignore files from .eslintignore?

<details> <summary>Click to expand</summary>

ESLint throws out warning File ignored because of a matching ignore pattern. Use "--no-ignore" to override warnings that breaks the linting process ( if you used --max-warnings=0 which is recommended ).

ESLint < 7

<details> <summary>Click to expand</summary>

Based on the discussion from this issue, it was decided that using the outlined scriptis the best route to fix this.

So you can setup a .lintstagedrc.js config file to do this:

import { CLIEngine } from 'eslint'

export default {
  '*.js': (files) => {
    const cli = new CLIEngine({})
    return 'eslint --max-warnings=0 ' + files.filter((file) => !cli.isPathIgnored(file)).join(' ')
  },
}
</details>

ESLint >= 7

<details> <summary>Click to expand</summary>

In versions of ESLint > 7, isPathIgnored is an async function and now returns a promise. The code below can be used to reinstate the above functionality.

Since 10.5.3, any errors due to a bad ESLint config will come through to the console.

import { ESLint } from 'eslint'

const removeIgnoredFiles = async (files) => {
  const eslint = new ESLint()
  const isIgnored = await Promise.all(
    files.map((file) => {
      return eslint.isPathIgnored(file)
    })
  )
  const filteredFiles = files.filter((_, i) => !isIgnored[i])
  return filteredFiles.join(' ')
}

export default {
  '**/*.{ts,tsx,js,jsx}': async (files) => {
    const filesToLint = await removeIgnoredFiles(files)
    return [`eslint --max-warnings=0 ${filesToLint}`]
  },
}
</details>

ESLint >= 8.51.0 && Flat ESLint config

<details> <summary>Click to expand</summary>

ESLint v8.51.0 introduced --no-warn-ignored CLI flag. It suppresses the warning File ignored because of a matching ignore pattern. Use "--no-ignore" to override warning, so manually ignoring files via eslint.isPathIgnored is no longer necessary.

{
  "*.js": "eslint --max-warnings=0 --no-warn-ignored"
}

NOTE: --no-warn-ignored flag is only available when Flat ESLint config is used.

</details> </details>