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Jul 31, 2023
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docs: mention EXPERIMENTAL_useProjectService in parser package docs #7352

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docs: mention EXPERIMENTAL_useProjectService in parser package docs
JoshuaKGoldberg Jul 28, 2023
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nit: projects
JoshuaKGoldberg Jul 28, 2023
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27 changes: 27 additions & 0 deletions docs/packages/Parser.mdx
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Expand Up @@ -249,6 +249,33 @@ Please only submit bug reports when using the officially supported version.
=============
```

### `EXPERIMENTAL_useProjectService`

An experimental alternative to `parserOptions.project`.
This directs the parser to use a more seamless TypeScript API to generate type information for rules.
It will automatically detect the TSConfig for each file (like `project: true`), and will also allow type information to be computed for JavaScript files without the `allowJs` compiler option (unlike `project: true`).

```js
module.exports = {
parser: '@typescript-eslint/parser',
parserOptions: {
EXPERIMENTAL_useProjectService: true,
},
};
```

This option should bring two main benefits:

- Simpler configurations: most projects shouldn't need to explicitly configure `project` paths or create `tsconfig.eslint.json`s
- Improved performance: this API is optimized on the TypeScript side for speed
- Initial versions of this option demonstrated performance changes in subsets of the typescript-eslint monorepo ranging from 11% slower to 70% faster

We're hopeful this option will eventually become the standard way to enable typed linting.
It switches the parser from manually creating TypeScript programs to instead calling the same "project services" API used by editors such as VS Code.
However, because it's so new and untested, we're keeping it under the `EXPERIMENTAL_` prefix for at least all of the `6.X` versions.
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fyi @jakebailey, just in case our phrasing is offputting for TypeScript-ers. I have a reminder set to merge this in time for our weekly deployment on Monday.


See [feat(typescript-estree): add EXPERIMENTAL_useProjectService option to use TypeScript project service](https://github.com/typescript-eslint/typescript-eslint/pull/6754) for more information.

## Utilities

### `createProgram(configFile, projectDirectory)`
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