eslint-plugin-yml

Introduction

eslint-plugin-yml is ESLint plugin provides linting rules for YAML.

Features

This ESLint plugin provides linting rules for YAML.

• You can use ESLint to lint YAML.
• You can find out the problem with your YAML files.
• You can apply consistent code styles to your YAML files.
• Supports Vue SFC custom blocks such as <i18n lang="yaml">.
  Requirements vue-eslint-parser v7.3.0 and above.
• Supports ESLint directives. e.g. # eslint-disable-next-line
• You can check your code in real-time using the ESLint editor integrations.

You can check on the Online DEMO.

How is it different from other YAML plugins?

Plugins that do not use AST

e.g. eslint-plugin-yaml

These plugins use the processor to parse and return the results independently, without providing the ESLint engine with AST and source code text.

Plugins don't provide AST, so you can't use directive comments (e.g. # eslint-disable).
Plugins don't provide source code text, so you can't use it with plugins and rules that use text (e.g. eslint-plugin-prettier, eol-last).

eslint-plugin-yml works by providing AST and source code text to ESLint.

Documentation

See documents.

Installation

npm install --save-dev eslint eslint-plugin-yml

Requirements

• ESLint v9.38.0 and above
• Node.js v20.19.0 or higher (in the 20.x line), v22.13.0 or higher (in the 22.x line), or v24.0.0 and above

Usage

Configuration

Use eslint.config.js file to configure rules. See also: https://eslint.org/docs/latest/use/configure/configuration-files-new.

Example eslint.config.js:

import eslintPluginYml from 'eslint-plugin-yml';
export default [
  // add more generic rule sets here, such as:
  // js.configs.recommended,
  ...eslintPluginYml.configs.recommended,
  {
    rules: {
      // override/add rules settings here, such as:
    // 'yml/rule-name': 'error'
    }
  }
];

This plugin provides configs:

• *.configs.base ... Configuration to enable correct YAML parsing.
• *.configs.recommended ... Above, plus rules to prevent errors or unintended behavior.
• *.configs.standard ... Above, plus rules to enforce the common stylistic conventions.
• *.configs.prettier ... Turn off rules that may conflict with Prettier.

See the rule list to get the rules that this plugin provides.

Note: The *.configs['flat/*'] configs are still available for backward compatibility, but it is recommended to use the new config names without the flat/ prefix.

Parser Configuration

If you have specified a parser, you need to configure a parser for .yaml.

For example, if you are using the "@babel/eslint-parser", configure it as follows:

import eslintPluginYml from 'eslint-plugin-yml';
import babelParser from '@babel/eslint-parser';

export default [
  ...eslintPluginYml.configs.standard,
  {
    files: ['**/*.js'],
    languageOptions: {
      parser: babelParser,
    },
  },
  // YAML files are already configured by the plugin
];

Parser Options

The following parser options for yaml-eslint-parser are available by specifying them in parserOptions in the ESLint configuration file.

import eslintPluginYml from 'eslint-plugin-yml';

export default [
  ...eslintPluginYml.configs.recommended,
  {
    files: ['**/*.yaml', '**/*.yml'],
    languageOptions: {
      parserOptions: {
        defaultYAMLVersion: '1.2',
      },
    },
  },
];

See also https://github.com/ota-meshi/yaml-eslint-parser#readme.

Running ESLint from the command line

With ESLint v9 and flat config, ESLint automatically lints all files matched by your config. You typically don't need the --ext option anymore.

Examples:

eslint .
eslint "src/**/*.{js,yaml,yml}"

Languages

This plugin provides the following language identifiers for use in ESLint configurations:

• yml/yaml ... YAML files

For example, to apply settings specifically to YAML files, you can use the language field in your ESLint configuration:

import eslintPluginYml from 'eslint-plugin-yml';
export default [
  {
    files: ["*.yaml", "*.yml", "**/*.yaml", "**/*.yml"],
    plugins: {
      yml: eslintPluginYml,
    },
    language: "yml/yaml",
  }
]

The configuration above is included in the shareable configs provided by this plugin, so using configs is generally recommended.

See also https://eslint.org/docs/latest/use/configure/plugins#specify-a-language

Editor Integrations

Visual Studio Code

Use the dbaeumer.vscode-eslint extension that Microsoft provides officially.

You have to configure the eslint.validate option of the extension to check .yaml files, because the extension targets only *.js or *.jsx files by default.

Example .vscode/settings.json:

{
  "eslint.validate": [
    "javascript",
    "javascriptreact",
    "yaml",
    "github-actions-workflow" // for GitHub Actions workflow files
  ]
}

JetBrains WebStorm IDEs

In any of the JetBrains IDEs you can configure the linting scope. Following the steps in their help document, you can add YAML files to the scope like so:

1. Open the Settings/Preferences dialog, go to Languages and Frameworks | JavaScript | Code Quality Tools | ESLint, and select Automatic ESLint configuration or Manual ESLint configuration.
2. In the Run for files field, update the pattern that defines the set of files to be linted to include YAML files as well:

{**/*,*}.{js,ts,jsx,tsx,html,vue,yaml,yml}
                                 ^^^^ ^^^

Rules

The --fix option on the command line automatically fixes problems reported by rules which have a wrench below.
The rules with the following star are included in the config.

YAML Rules

Rule ID	Description	Fixable	RECOMMENDED	STANDARD
yml/block-mapping-colon-indicator-newline	enforce consistent line breaks after : indicator
yml/block-mapping-question-indicator-newline	enforce consistent line breaks after ? indicator
yml/block-mapping	require or disallow block style mappings.
yml/block-sequence-hyphen-indicator-newline	enforce consistent line breaks after - indicator
yml/block-sequence	require or disallow block style sequences.
yml/file-extension	enforce YAML file extension
yml/indent	enforce consistent indentation
yml/key-name-casing	enforce naming convention to key names
yml/no-empty-document	disallow empty document
yml/no-empty-key	disallow empty mapping keys
yml/no-empty-mapping-value	disallow empty mapping values
yml/no-empty-sequence-entry	disallow empty sequence entries
yml/no-tab-indent	disallow tabs for indentation.
yml/no-trailing-zeros	disallow trailing zeros for floats
yml/plain-scalar	require or disallow plain style scalar.
yml/quotes	enforce the consistent use of either double, or single quotes
yml/require-string-key	disallow mapping keys other than strings
yml/sort-keys	require mapping keys to be sorted
yml/sort-sequence-values	require sequence values to be sorted
yml/vue-custom-block/no-parsing-error	disallow parsing errors in Vue custom blocks

Extension Rules

Rule ID	Description	Fixable	RECOMMENDED	STANDARD
yml/flow-mapping-curly-newline	enforce consistent line breaks inside braces
yml/flow-mapping-curly-spacing	enforce consistent spacing inside braces
yml/flow-sequence-bracket-newline	enforce linebreaks after opening and before closing flow sequence brackets
yml/flow-sequence-bracket-spacing	enforce consistent spacing inside flow sequence brackets
yml/key-spacing	enforce consistent spacing between keys and values in mapping pairs
yml/no-irregular-whitespace	disallow irregular whitespace
yml/no-multiple-empty-lines	disallow multiple empty lines
yml/no-trailing-spaces	disallow trailing whitespace at the end of lines
yml/spaced-comment	enforce consistent spacing after the # in a comment

To Do More Verification

Verify using JSON Schema

You can verify using JSON Schema by checking and installing eslint-plugin-json-schema-validator.

Verify the Vue I18n message resource files

You can verify the message files by checking and installing @intlify/eslint-plugin-vue-i18n.

Semantic Versioning Policy

eslint-plugin-yml follows Semantic Versioning and ESLint's Semantic Versioning Policy.

Contributing

Welcome contributing!

Please use GitHub's Issues/PRs.

Development Tools

• npm test runs tests and measures coverage.
• npm run update runs in order to update readme and recommended configuration.

Working With Rules

This plugin uses yaml-eslint-parser for the parser. Check here to find out about AST.

Related Packages

• eslint-plugin-jsonc ... ESLint plugin for JSON, JSON with comments (JSONC) and JSON5.
• eslint-plugin-toml ... ESLint plugin for TOML.
• eslint-plugin-json-schema-validator ... ESLint plugin that validates data using JSON Schema Validator.
• jsonc-eslint-parser ... JSON, JSONC and JSON5 parser for use with ESLint plugins.
• yaml-eslint-parser ... YAML parser for use with ESLint plugins.
• toml-eslint-parser ... TOML parser for use with ESLint plugins.

License

See the LICENSE file for license rights and limitations (MIT).