user-guide.md

User Guide

💿 Installation

npm install --save-dev eslint eslint-plugin-svelte svelte

::: tip Requirements

• ESLint v7.0.0 and above
• Node.js v14.17.x, v16.x and above

:::

📖 Usage

Configuration

Use .eslintrc.* file to configure rules. See also: https://eslint.org/docs/user-guide/configuring.

Example .eslintrc.js:

module.exports = {
  extends: [
    // add more generic rule sets here, such as:
    // 'eslint:recommended',
    "plugin:svelte/recommended",
  ],
  rules: {
    // override/add rules settings here, such as:
    // 'svelte/rule-name': 'error'
  },
}

This plugin provides configs:

• plugin:svelte/base ... Configuration to enable correct Svelte parsing.
• plugin:svelte/recommended ... Above, plus rules to prevent errors or unintended behavior.
• plugin:svelte/prettier ... Turns off rules that may conflict with Prettier (You still need to configure prettier to work with svelte yourself, for example by using prettier-plugin-svelte.).

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

::: warning ❗ Attention

The eslint-plugin-svelte can not be used with the eslint-plugin-svelte3. If you are using eslint-plugin-svelte3 you need to remove it.

  "plugins": [
-   "svelte3"
  ]

:::

Parser Configuration

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

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

module.exports = {
  // ...
  extends: ["plugin:svelte/recommended"],
  // ...
  parser: "@babel/eslint-parser",
  // Add an `overrides` section to add a parser configuration for svelte.
  overrides: [
    {
      files: ["*.svelte"],
      parser: "svelte-eslint-parser",
    },
    // ...
  ],
  // ...
}

For example, if you are using the "@typescript-eslint/parser", and if you want to use TypeScript in <script> of .svelte, you need to add more parserOptions configuration.

module.exports = {
  // ...
  extends: ["plugin:svelte/recommended"],
  // ...
  parser: "@typescript-eslint/parser",
  parserOptions: {
    // ...
    project: "path/to/your/tsconfig.json",
    extraFileExtensions: [".svelte"], // This is a required setting in `@typescript-eslint/parser` v4.24.0.
  },
  overrides: [
    {
      files: ["*.svelte"],
      parser: "svelte-eslint-parser",
      // Parse the `<script>` in `.svelte` as TypeScript by adding the following configuration.
      parserOptions: {
        parser: "@typescript-eslint/parser",
      },
    },
    // ...
  ],
  // ...
}

If you have a mix of TypeScript and JavaScript in your project, use a multiple parser configuration.

module.exports = {
  // ...
  overrides: [
    {
      files: ["*.svelte"],
      parser: "svelte-eslint-parser",
      parserOptions: {
        parser: {
          // Specify a parser for each lang.
          ts: "@typescript-eslint/parser",
          js: "espree",
          typescript: "@typescript-eslint/parser",
        },
      },
    },
    // ...
  ],
  // ...
}

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

settings.svelte

You can change the behavior of this plugin with some settings.

• ignoreWarnings (optional) ... Specifies an array of rules that ignore reports in the template.
  For example, set rules on the template that cannot avoid false positives.
• compileOptions (optional) ... Specifies options for Svelte compile. Effects rules that use Svelte compile. The target rules are svelte/valid-compile and svelte/no-unused-svelte-ignore. Note that it has no effect on ESLint's custom parser.
  • postcss (optional) ... Specifies options related to PostCSS. You can disable the PostCSS process by specifying false.
    • configFilePath (optional) ... Specifies the path of the directory containing the PostCSS configuration.

e.g.

module.exports = {
  // ...
  settings: {
    svelte: {
      ignoreWarnings: [
        "@typescript-eslint/no-unsafe-assignment",
        "@typescript-eslint/no-unsafe-member-access",
      ],
      compileOptions: {
        postcss: {
          configFilePath: "./path/to/my/postcss.config.js",
        },
      },
    },
  },
  // ...
}

Running ESLint from the command line

If you want to run eslint from the command line, make sure you include the .svelte extension using the --ext option or a glob pattern, because ESLint targets only .js files by default.

Examples:

eslint --ext .js,.svelte src
eslint "src/**/*.{js,svelte}"

💻 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 .svelte files, because the extension targets only *.js or *.jsx files by default.

Example .vscode/settings.json:

{
  "eslint.validate": ["javascript", "javascriptreact", "svelte"]
}

❓ FAQ

Parsing the .svelte file fails

You should check the parser configuration.