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Svelte parser for ESLint

sveltejs.github.io/svelte-eslint-parser/

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svelte-eslint-parser

Svelte parser forESLint

Live DEMO •Discord

Motivation

Thesvelte-eslint-parser aims to make it easy to create your own ESLint rules forSvelte.

eslint-plugin-svelte is an ESLint plugin built upon this parser, and it alreadyimplements some rules.

ESLint Plugins Using svelte-eslint-parser

eslint-plugin-svelte

ESLint plugin for Svelte.
Provides a variety of template-based checks using the Svelte AST.

@intlify/eslint-plugin-svelte

ESLint plugin for internationalization (i18n) in Svelte applications, offering helpful i18n-related rules.

Installation

npm install --save-dev eslint svelte-eslint-parser

Usage

ESLint Config (`eslint.config.js`)

importjsfrom"@eslint/js";importsvelteParserfrom"svelte-eslint-parser";exportdefault[js.configs.recommended,{files:["**/*.svelte","*.svelte",// Need to specify the file extension for Svelte 5 with rune symbols"**/*.svelte.js","*.svelte.js","**/*.svelte.ts","*.svelte.ts",],languageOptions:{parser:svelteParser,},},];

CLI

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

Options

TheparserOptions for this parser generally match whatespree—ESLint's default parser—supports.

For example:

importsvelteParserfrom"svelte-eslint-parser";exportdefault[// ...{files:[// Set .svelte/.js/.ts files. See above for more details.],languageOptions:{parser:svelteParser,parserOptions:{sourceType:"module",ecmaVersion:2024,ecmaFeatures:{globalReturn:false,impliedStrict:false,jsx:false,},},},},];

parserOptions.parser

Use theparserOptions.parser property to define a custom parser for<script> tags. Any additional parser options (besides the parser itself) are passed along to the specified parser.

importtsParserfrom"@typescript-eslint/parser";exportdefault[{files:[// Set .svelte/.js/.ts files. See above for more details.],languageOptions:{parser:svelteParser,parserOptions:{parser:tsParser,},},},];

Using TypeScript in`<script>`

If you use@typescript-eslint/parser for TypeScript within<script> of.svelte files, additional configuration is needed. For example:

importtsParserfrom"@typescript-eslint/parser";exportdefault[// Other config for non-Svelte files{languageOptions:{parser:tsParser,parserOptions:{project:"path/to/your/tsconfig.json",extraFileExtensions:[".svelte"],},},},// Svelte config{files:[// Set .svelte/.js/.ts files. See above for more details.],languageOptions:{parser:svelteParser,// Parse the `<script>` in `.svelte` as TypeScript by adding the following configuration.parserOptions:{parser:tsParser,},},},];

Multiple parsers

To switch parsers for each language, provide an object:

importtsParserfrom"@typescript-eslint/parser";importespreefrom"espree";exportdefault[{files:[// Set .svelte/.js/.ts files. See above for more details.],languageOptions:{parser:svelteParser,parserOptions:{parser:{ts:tsParser,js:espree,typescript:tsParser,},},},},];

parserOptions.svelteConfig

If you useeslint.config.js, you can specify asvelte.config.js file viaparserOptions.svelteConfig.

importsvelteConfigfrom"./svelte.config.js";exportdefault[{files:[// Set .svelte/.js/.ts files. See above for more details.],languageOptions:{parser:svelteParser,parserOptions:{        svelteConfig,},},},];

IfparserOptions.svelteConfig is not set, the parser attempts to statically read some config fromsvelte.config.js.

parserOptions.svelteFeatures

You can configure how Svelte-specific features are parsed viaparserOptions.svelteFeatures.

For example:

exportdefault[{files:[// Set .svelte/.js/.ts files. See above for more details.],languageOptions:{parser:svelteParser,parserOptions:{svelteFeatures:{// This is for Svelte 5. The default is true.// If false, ESLint won't recognize rune symbols.// If not specified, the parser tries to read compilerOptions.runes from `svelte.config.js`.// If `parserOptions.svelteConfig` is not given and static analysis fails, it defaults to true.runes:true,},},},},];

Editor Integrations

Visual Studio Code

Use thedbaeumer.vscode-eslint extension provided by Microsoft.

By default, it only targets*.js and*.jsx, so you need to configure.svelte file support. For example, in.vscode/settings.json:

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

Usage for Custom Rules / Plugins

SeeAST.md for the AST specification. You can explore it on theLive DEMO.
This parser generates its ownScopeManager. Check theLive DEMO.
Several rules are [already implemented] in [eslint-plugin-svelte], and their source code can be a helpful reference.