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https://github.com/sveltejs/svelte-eslint-parser

Svelte parser for ESLint
https://github.com/sveltejs/svelte-eslint-parser

eslint eslint-custom-parser eslint-parser parser svelte sveltejs

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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]
> This README is in development.\
> Please refer to the README for the version you are using.\
> For example,

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## โคด๏ธ 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.

## ๐Ÿ’ฟ Installation

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

## ๐Ÿ“– 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,
},
},
];
```

### CLI

```console
$ eslint "src/**/*.{js,svelte}"
# or
$ eslint src --ext .svelte
```

## ๐Ÿ”ง Options

[`parserOptions`] has the same properties as what [espree](https://github.com/eslint/espree#usage), the default parser of ESLint, is supporting.
For example:

```js
import svelteParser from "svelte-eslint-parser";
export default [
// ...
{
files: ["**/*.svelte", "*.svelte"],
languageOptions: {
parser: svelteParser,
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 `` 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,
},
},
},
];
```

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,
},
},
// ...
},
];
```

#### 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,
},
},
},
},
];
```

### 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: {
// 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,
},
},
},
},
];
```

### Runes support

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,
/* ... */
},
},
},
];
```

## :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/