svelte-eslint-parser
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Svelte parser for ESLint
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# svelte-eslint-parser
[Svelte] parser for [ESLint].
You can check it on [Online DEMO](https://sveltejs.github.io/svelte-eslint-parser/playground).
**_Note that this parser has experimental support for Svelte v5, but may break with new versions of Svelte v5._**
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## ⤴️ Motivation
The [svelte-eslint-parser] aims to make it easy to create your own ESLint rules for [Svelte].
The [`eslint-plugin-svelte`] is an ESLint plugin that uses the [svelte-eslint-parser]. I have already [implemented some rules].
[`eslint-plugin-svelte`]: https://github.com/sveltejs/eslint-plugin-svelte
[implemented some rules]: https://sveltejs.github.io/eslint-plugin-svelte/rules/
### ESLint Plugins Using svelte-eslint-parser
#### [eslint-plugin-svelte](https://sveltejs.github.io/eslint-plugin-svelte/)
ESLint plugin for Svelte.
It provides many unique check rules by using the template AST.
#### [@intlify/eslint-plugin-svelte](https://github.com/intlify/eslint-plugin-svelte)
ESLint plugin for internationalization (i18n) with Svelte.
It provides rules to help internationalization your application created with Svelte.
## ❗ Attention
The [svelte-eslint-parser] can not be used with the [eslint-plugin-svelte3].
[svelte-eslint-parser]: https://github.com/sveltejs/svelte-eslint-parser
## 💿 Installation
```bash
npm install --save-dev eslint svelte-eslint-parser
```
## 📖 Usage
1. Write `parser` option into your ESLint Config file.
2. Use glob patterns or `--ext .svelte` CLI option.
### ESLint Config (`eslint.config.js`)
```js
import js from "@eslint/js";
import svelteParser from "svelte-eslint-parser";
export default [
js.configs.recommended,
{
files: ["**/*.svelte", "*.svelte"],
languageOptions: {
parser: svelteParser,
},
},
];
```
### ESLint Config (`.eslintrc.*`)
```json
{
"extends": "eslint:recommended",
"overrides": [
{
"files": ["*.svelte"],
"parser": "svelte-eslint-parser"
}
]
}
```
### CLI
```console
$ eslint "src/**/*.{js,svelte}"
# or
$ eslint src --ext .svelte
```
## 🔧 Options
[`parserOptions`] has the same properties as what [espree](https://github.com/eslint/espree#usage), the default parser of ESLint, is supporting.
For example:
```json
{
"parserOptions": {
"sourceType": "module",
"ecmaVersion": 2021,
"ecmaFeatures": {
"globalReturn": false,
"impliedStrict": false,
"jsx": false
}
}
}
```
[`parserOptions`]: https://eslint.org/docs/latest/use/configure/parser#configure-parser-options
### parserOptions.parser
You can use `parserOptions.parser` property to specify a custom parser to parse `<script>` tags.
Other properties than parser would be given to the specified parser.
For example in `eslint.config.js`:
```js
import tsParser from "@typescript-eslint/parser";
export default [
{
files: ["**/*.svelte", "*.svelte"],
languageOptions: {
parser: svelteParser,
parserOptions: {
parser: tsParser,
},
},
},
];
```
For example in `.eslintrc.*`:
```json
{
"parser": "svelte-eslint-parser",
"parserOptions": {
"parser": "@typescript-eslint/parser"
}
}
```
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.
For example in `eslint.config.js`:
```js
import tsParser from "@typescript-eslint/parser";
export default [
// ...
{
// ...
languageOptions: {
parser: tsParser,
parserOptions: {
// ...
project: "path/to/your/tsconfig.json",
extraFileExtensions: [".svelte"], // This is a required setting in `@typescript-eslint/parser` v4.24.0.
},
},
},
{
files: ["**/*.svelte", "*.svelte"],
languageOptions: {
parser: svelteParser,
// Parse the `<script>` in `.svelte` as TypeScript by adding the following configuration.
parserOptions: {
parser: tsParser,
},
},
// ...
},
];
```
For example in `.eslintrc.*`:
```js
module.exports = {
// ...
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",
},
},
// ...
],
// ...
};
```
#### Multiple parsers
If you want to switch the parser for each lang, specify the object.
For example in `eslint.config.js`:
```js
import tsParser from "@typescript-eslint/parser";
import espree from "espree";
export default [
{
files: ["**/*.svelte", "*.svelte"],
languageOptions: {
parser: svelteParser,
parserOptions: {
parser: {
ts: tsParser,
js: espree,
typescript: tsParser,
},
},
},
},
];
```
For example in `.eslintrc.*`:
```json
{
"parser": "svelte-eslint-parser",
"parserOptions": {
"parser": {
"ts": "@typescript-eslint/parser",
"js": "espree",
"typescript": "@typescript-eslint/parser"
}
}
}
```
### parserOptions.svelteConfig
If you are using `eslint.config.js`, you can provide a `svelte.config.js` in the `parserOptions.svelteConfig` property.
For example:
```js
import svelteConfig from "./svelte.config.js";
export default [
{
files: ["**/*.svelte", "*.svelte"],
languageOptions: {
parser: svelteParser,
parserOptions: {
svelteConfig: svelteConfig,
},
},
},
];
```
If `parserOptions.svelteConfig` is not specified, some config will be statically parsed from the `svelte.config.js` file.
The `.eslintrc.*` style configuration cannot load `svelte.config.js` because it cannot use ESM. We recommend using the `eslint.config.js` style configuration.
### parserOptions.svelteFeatures
You can use `parserOptions.svelteFeatures` property to specify how to parse related to Svelte features.
For example in `eslint.config.js`:
```js
export default [
{
files: ["**/*.svelte", "*.svelte"],
languageOptions: {
parser: svelteParser,
parserOptions: {
svelteFeatures: {
/* -- Experimental Svelte Features -- */
/* It may be changed or removed in minor versions without notice. */
// This option is for Svelte 5. The default value is `true`.
// If `false`, ESLint will not recognize rune symbols.
// If not configured this option, The parser will try to read the option from `compilerOptions.runes` from `svelte.config.js`.
// If `parserOptions.svelteConfig` is not specified and the file cannot be parsed by static analysis, it will behave as `true`.
runes: true,
/* -- Experimental Svelte Features -- */
/* It may be changed or removed in minor versions without notice. */
// Whether to parse the `generics` attribute.
// See https://github.com/sveltejs/rfcs/pull/38
experimentalGenerics: false,
},
},
},
},
];
```
For example in `.eslintrc.*`:
```jsonc
{
"parser": "svelte-eslint-parser",
"parserOptions": {
"svelteFeatures": {
/* -- Experimental Svelte Features -- */
/* It may be changed or removed in minor versions without notice. */
// This option is for Svelte 5. The default value is `true`.
// If `false`, ESLint will not recognize rune symbols.
// If not configured this option, The parser will try to read the option from `compilerOptions.runes` from `svelte.config.js`.
// If `parserOptions.svelteConfig` is not specified and the file cannot be parsed by static analysis, it will behave as `true`.
"runes": true,
/* -- Experimental Svelte Features -- */
/* It may be changed or removed in minor versions without notice. */
// Whether to parse the `generics` attribute.
// See https://github.com/sveltejs/rfcs/pull/38
"experimentalGenerics": false,
},
},
}
```
### Runes support
**_This is an experimental feature. It may be changed or removed in minor versions without notice._**
If you install Svelte v5 the parser will be able to parse runes, and will also be able to parse `*.js` and `*.ts` files.
If you don't want to use Runes, you may need to configure. Please read [parserOptions.svelteFeatures](#parseroptionssveltefeatures) for more details.
When using this mode in an ESLint configuration, it is recommended to set it per file pattern as below.
For example in `eslint.config.js`:
```js
import svelteConfig from "./svelte.config.js";
export default [
{
files: ["**/*.svelte", "*.svelte"],
languageOptions: {
parser: svelteParser,
parserOptions: {
parser: "...",
svelteConfig,
/* ... */
},
},
},
{
files: ["**/*.svelte.js", "*.svelte.js"],
languageOptions: {
parser: svelteParser,
parserOptions: {
svelteConfig,
/* ... */
},
},
},
{
files: ["**/*.svelte.ts", "*.svelte.ts"],
languageOptions: {
parser: svelteParser,
parserOptions: {
parser: "...(ts parser)...",
svelteConfig,
/* ... */
},
},
},
];
```
For example in `.eslintrc.*`:
```jsonc
{
"overrides": [
{
"files": ["*.svelte"],
"parser": "svelte-eslint-parser",
"parserOptions": {
"parser": "...",
/* ... */
},
},
{
"files": ["*.svelte.js"],
"parser": "svelte-eslint-parser",
"parserOptions": {
/* ... */
},
},
{
"files": ["*.svelte.ts"],
"parser": "svelte-eslint-parser",
"parserOptions": {
"parser": "...(ts parser)...",
/* ... */
},
},
],
}
```
## :computer: Editor Integrations
### Visual Studio Code
Use the [dbaeumer.vscode-eslint](https://marketplace.visualstudio.com/items?itemName=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**:
```json
{
"eslint.validate": ["javascript", "javascriptreact", "svelte"]
}
```
## Usage for Custom Rules / Plugins
- [AST.md](./docs/AST.md) is AST specification. You can check it on the [Online DEMO](https://sveltejs.github.io/svelte-eslint-parser/).
- The parser will generate its own [ScopeManager](https://eslint.org/docs/developer-guide/scope-manager-interface). You can check it on the [Online DEMO](https://sveltejs.github.io/svelte-eslint-parser/scope).
- I have already [implemented some rules] in the [`eslint-plugin-svelte`]. The source code for these rules will be helpful to you.
## :beers: Contributing
Welcome contributing!
Please use GitHub's Issues/PRs.
See also the documentation for the internal mechanism.
- [internal-mechanism.md](./docs/internal-mechanism.md)
## :lock: License
See the [LICENSE](LICENSE) file for license rights and limitations (MIT).
[Svelte]: https://svelte.dev/
[ESLint]: https://eslint.org/
[eslint-plugin-svelte3]: https://github.com/sveltejs/eslint-plugin-svelte3