lint-staged

What is lint-staged?

The lint-staged npm package is used to run linters on staged git files. It allows you to run specific commands before committing, ensuring that only clean, linted code gets committed to your repository. This helps in maintaining code quality and reducing the chances of committing code with errors or that doesn't adhere to the project's coding standards.

What are lint-staged's main functionalities?

Running linters on staged files

This configuration in package.json will run ESLint on staged JavaScript files and Stylelint on staged CSS files, automatically fixing any fixable issues.

"lint-staged": {
  "*.js": "eslint --fix",
  "*.css": "stylelint --fix"
}

Running custom scripts

This configuration will run markdownlint-cli2 on staged Markdown files to ensure they meet the project's markdown style requirements.

"lint-staged": {
  "*.md": "npx markdownlint-cli2"
}

Using with pre-commit hooks

This configuration sets up Husky to run lint-staged as a pre-commit hook, ensuring that the linters are run automatically before each commit.

{
  "husky": {
    "hooks": {
      "pre-commit": "lint-staged"
    }
  }
}

Other packages similar to lint-staged

pretty-quick

pretty-quick is an npm package that runs Prettier on your changed files. It is similar to lint-staged but is specifically focused on formatting with Prettier rather than running arbitrary linters or tasks.

husky

Husky can be used to manage Git hooks and can run tasks on commit, push, and more. While it doesn't run linters on staged files by itself, it is often used in conjunction with lint-staged to trigger linters before a commit.

lefthook

Lefthook is a fast and powerful Git hooks manager for Node.js, Ruby, or any other type of projects. It can run linters and custom scripts similar to lint-staged, but it also provides additional features like parallel task execution and support for multiple programming languages.

README

🚫💩 lint-staged

---

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

✔ Preparing lint-staged...
❯ 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...

See asciinema video

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

• Introductory Medium post - Andrey Okonetchnikov, 2016
• Running Jest Tests Before Each Git Commit - Ben McCormick, 2017
• AgentConf presentation - Andrey Okonetchnikov, 2018
• SurviveJS interview - Juho Vepsäläinen and Andrey Okonetchnikov, 2018
• Prettier your CSharp with dotnet-format and lint-staged

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.

Changelog

See Releases.

Migration

v15

• Since v15.0.0 lint-staged no longer supports Node.js 16. Please upgrade your Node.js version to at least 18.12.0.

v14

• Since v14.0.0 lint-staged no longer supports Node.js 14. Please upgrade your Node.js version to at least 16.14.0.

v13

• Since v13.0.0 lint-staged no longer supports Node.js 12. Please upgrade your Node.js version to at least 14.13.1, or 16.0.0 onward.
• Version v13.3.0 was incorrectly released including code of version v14.0.0. This means the breaking changes of v14 are also included in v13.3.0, the last v13 version released

v12

• Since v12.0.0 lint-staged is a pure ESM module, so make sure your Node.js version is at least 12.20.0, 14.13.1, or 16.0.0. Read more about ESM modules from the official Node.js Documentation site here.

v10

• From v10.0.0 onwards any new modifications to originally staged files will be automatically added to the commit. If your task previously contained a git add step, please remove this. The automatic behaviour ensures there are less race-conditions, since trying to run multiple git operations at the same time usually results in an error.
• From v10.0.0 onwards, lint-staged uses git stashes to improve speed and provide backups while running. Since git stashes require at least an initial commit, you shouldn't run lint-staged in an empty repo.
• From v10.0.0 onwards, lint-staged requires Node.js version 10.13.0 or later.
• From v10.0.0 onwards, lint-staged will abort the commit if linter tasks undo all staged changes. To allow creating an empty commit, please use the --allow-empty option.

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

• --allow-empty: By default, when linter tasks undo all staged changes, lint-staged will exit with an error and abort the commit. Use this flag to allow creating empty git commits.
• --concurrent [number|boolean]: Controls the concurrency of tasks being run by lint-staged. NOTE: This does NOT affect the concurrency of subtasks (they will always be run sequentially). Possible values are:
  • false: Run all tasks serially
  • true (default) : Infinite concurrency. Runs as many tasks in parallel as possible.
  • {number}: Run the specified number of tasks in parallel, where 1 is equivalent to false.
• --config [path]: Manually specify a path to a config file or npm package name. Note: when used, lint-staged won't perform the config file search and will print an error if the specified file cannot be found. If '-' is provided as the filename then the config will be read from stdin, allowing piping in the config like cat my-config.json | npx lint-staged --config -.
• --cwd [path]: By default tasks run in the current working directory. Use the --cwd some/directory to override this. The path can be absolute or relative to the current working directory.
• --debug: Run in debug mode. When set, it does the following:
  • uses debug internally to log additional information about staged files, commands being executed, location of binaries, etc. Debug logs, which are automatically enabled by passing the flag, can also be enabled by setting the environment variable $DEBUG to lint-staged*.
  • uses verbose renderer for listr2; this causes serial, uncoloured output to the terminal, instead of the default (beautified, dynamic) output. (the verbose renderer can also be activated by setting the TERM=dumb or NODE_ENV=test environment variables)
• --diff: By default linters are filtered against all files staged in git, generated from git diff --staged. This option allows you to override the --staged flag with arbitrary revisions. For example to get a list of changed files between two branches, use --diff="branch1...branch2". You can also read more from about git diff and gitrevisions. This option also implies --no-stash.
• --diff-filter: By default only files that are added, copied, modified, or renamed are included. Use this flag to override the default ACMR value with something else: added (A), copied (C), deleted (D), modified (M), renamed (R), type changed (T), unmerged (U), unknown (X), or pairing broken (B). See also the git diff docs for --diff-filter.
• --max-arg-length: long commands (a lot of files) are automatically split into multiple chunks when it detects the current shell cannot handle them. Use this flag to override the maximum length of the generated command string.
• --no-stash: By default a backup stash will be created before running the tasks, and all task modifications will be reverted in case of an error. This option will disable creating the stash, and instead leave all modifications in the index when aborting the commit. Can be re-enabled with --stash. This option also implies --no-hide-partially-staged.
• --no-hide-partially-staged: By default, unstaged changes from partially staged files will be hidden. This option will disable this behavior and include all unstaged changes in partially staged files. Can be re-enabled with --hide-partially-staged
• --quiet: Supress all CLI output, except from tasks.
• --relative: Pass filepaths relative to process.cwd() (where lint-staged runs) to tasks. Default is false.
• --shell: By default linter commands will be parsed for speed and security. This has the side-effect that regular shell scripts might not work as expected. You can skip parsing of commands with this option. To use a specific shell, use a path like --shell "/bin/bash".
• --verbose: Show task output even when tasks succeed. By default only failed output is shown.

Configuration

Lint-staged can be configured in many ways:

• lint-staged object in your package.json, or package.yaml
• .lintstagedrc file in JSON or YML format, or you can be explicit with the file extension:
  • .lintstagedrc.json
  • .lintstagedrc.yaml
  • .lintstagedrc.yml
• .lintstagedrc.mjs or lint-staged.config.mjs file in ESM format
  • the default export value should be a configuration: export default { ... }
• .lintstagedrc.cjs or lint-staged.config.cjs file in CommonJS format
  • the exports value should be a configuration: module.exports = { ... }
• lint-staged.config.js or .lintstagedrc.js in either ESM or CommonJS format, depending on whether your project's package.json contains the "type": "module" option or not.
• Pass a configuration file using the --config or -c flag

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:

• If the glob pattern contains no slashes (/), micromatch's matchBase option will be enabled, so globs match a file's basename regardless of directory:
  • "*.js" will match all JS files, like /test.js and /foo/bar/test.js
  • "!(*test).js" will match all JS files, except those ending in test.js, so foo.js but not foo.test.js
  • "!(*.css|*.js)" will match all files except CSS and JS files
• If the glob pattern does contain a slash (/), it will match for paths as well:
  • "./*.js" will match all JS files in the git repo root, so /test.js but not /foo/bar/test.js
  • "foo/**/*.js" will match all JS files inside the /foo directory, so /foo/bar/test.js but not /test.js

When matching, lint-staged will do the following

• Resolve the git root automatically, no configuration needed.
• Pick the staged files which are present inside the project directory.
• Filter them using the specified glob patterns.
• Pass absolute paths to the linters as arguments.

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"
}

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.

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.

Function signature

The function can also be async:

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

Example: Export a function to build your own matchers

Click to expand

// 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(' ')}`]
}

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

Click to expand

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

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

Click to expand

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

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

Click to expand

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

Example: Use your own globs

Click to expand

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(' ')}`]
  },
}

Example: Ignore files from match

Click to expand

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.

Example: Use relative paths for commands

Click to expand

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(' ')}`
  },
}

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

Click to expand

{
  "*.{js,jsx}": "eslint"
}

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

Click to expand

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

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

Reuse npm script

Click to expand

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"
}

Use environment variables with linting commands

Click to expand

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"]
}

Automatically fix code style with prettier for any format Prettier supports

Click to expand

{
  "*": "prettier --ignore-unknown --write"
}

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

Click to expand

{
  "*.{js,jsx,ts,tsx,md,html,css}": "prettier --write"
}

Stylelint for CSS with defaults and for SCSS with SCSS syntax

Click to expand

{
  "*.css": "stylelint",
  "*.scss": "stylelint --syntax=scss"
}

Run PostCSS sorting and Stylelint to check

Click to expand

{
  "*.scss": ["postcss --config path/to/your/config --replace", "stylelint"]
}

Minify the images

Click to expand

{
  "*.{png,jpeg,jpg,gif,svg}": "imagemin-lint-staged"
}

More about imagemin-lint-staged

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.

Typecheck your staged files with flow

Click to expand

{
  "*.{js,jsx}": "flow focus-check"
}

Integrate with Next.js

Click to expand

// .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],
}

Frequently Asked Questions

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

Click to expand

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

• In Git 2.36 we revamped the way how hooks are invoked. One change that is end-user visible is that the output of a hook is no longer directly connected to the standard output of "git" that spawns the hook, which was noticed post release. This is getting corrected. (merge a082345372 ab/hooks-regression-fix later to maint).

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

Can I use lint-staged via node?

Click to expand

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.

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

Click to expand

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!

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

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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).

Can I lint files outside of the current project folder?

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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.

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

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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"

Can I use lint-staged with ng lint

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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.

How can I ignore files from .eslintignore?

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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

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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(' ')
  },
}

ESLint >= 7

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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}`]
  },
}

ESLint >= 8.51.0 && Flat ESLint config

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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.

Changelog

15.2.9

Patch Changes

• #1463 b69ce2d Thanks @iiroj! - Set the maximum number of event listeners to the number of tasks. This should silence the console warning MaxListenersExceededWarning: Possible EventEmitter memory leak detected.