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# @rollup/plugin-typescript

🍣 A Rollup plugin for seamless integration between Rollup and Typescript.

## Requirements

This plugin requires an [LTS](https://github.com/nodejs/Release) Node version (v14.0.0+) and Rollup v2.14.0+. This plugin also requires at least [TypeScript 3.7](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html).

## Install

Using npm:

```console
npm install @rollup/plugin-typescript --save-dev
```

Note that both `typescript` and `tslib` are peer dependencies of this plugin that need to be installed separately.

## Why?

See [@rollup/plugin-babel](https://github.com/rollup/plugins/tree/master/packages/babel).

## Usage

Create a `rollup.config.js` [configuration file](https://www.rollupjs.org/guide/en/#configuration-files) and import the plugin:

```js
// rollup.config.js
import typescript from '@rollup/plugin-typescript';

export default {
  input: 'src/index.ts',
  output: {
    dir: 'output',
    format: 'cjs'
  },
  plugins: [typescript()]
};
```

Then call `rollup` either via the [CLI](https://www.rollupjs.org/guide/en/#command-line-reference) or the [API](https://www.rollupjs.org/guide/en/#javascript-api).

## Options

The plugin loads any [`compilerOptions`](http://www.typescriptlang.org/docs/handbook/compiler-options.html) from the `tsconfig.json` file by default. Passing options to the plugin directly overrides those options:

```js
...
export default {
  input: './main.ts',
  plugins: [
      typescript({ compilerOptions: {lib: ["es5", "es6", "dom"], target: "es5"}})
  ]
}
```

The following options are unique to `@rollup/plugin-typescript`:

### `exclude`

Type: `String` | `Array[...String]`<br>
Default: `null`

A [picomatch pattern](https://github.com/micromatch/picomatch), or array of patterns, which specifies the files in the build the plugin should _ignore_. By default no files are ignored.

### `include`

Type: `String` | `Array[...String]`<br>
Default: `null`

A [picomatch pattern](https://github.com/micromatch/picomatch), or array of patterns, which specifies the files in the build the plugin should operate on. By default all `.ts` and `.tsx` files are targeted.

### `filterRoot`

Type: `String` | `Boolean`<br>
Default: `rootDir` ?? `tsConfig.compilerOptions.rootDir` ?? `process.cwd()`

Optionally resolves the include and exclude patterns against a directory other than `process.cwd()`. If a String is specified, then the value will be used as the base directory. Relative paths will be resolved against `process.cwd()` first. If `false`, then the patterns will not be resolved against any directory.

By default, patterns resolve against the rootDir set in your TS config file.

This can fix plugin errors when parsing files outside the current working directory (process.cwd()).

### `tsconfig`

Type: `String` | `Boolean`<br>
Default: `true`

When set to false, ignores any options specified in the config file. If set to a string that corresponds to a file path, the specified file will be used as config file.

### `typescript`

Type: `import('typescript')`<br>
Default: _peer dependency_

Overrides the TypeScript module used for transpilation.

```js
typescript({
  typescript: require('some-fork-of-typescript')
});
```

### `tslib`

Type: `String`<br>
Default: _peer dependency_

Overrides the injected TypeScript helpers with a custom version.

```js
typescript({
  tslib: require.resolve('some-fork-of-tslib')
});
```

### `transformers`

Type: `{ [before | after | afterDeclarations]: TransformerFactory[] }`<br>
Default: `undefined`

Allows registration of TypeScript custom transformers at any of the supported stages:

- **before**: transformers will execute before the TypeScript's own transformers on raw TypeScript files
- **after**: transformers will execute after the TypeScript transformers on transpiled code
- **afterDeclarations**: transformers will execute after declaration file generation allowing to modify existing declaration files

Supported transformer factories:

- all **built-in** TypeScript custom transformer factories:

  - `import('typescript').TransformerFactory` annotated **TransformerFactory** bellow
  - `import('typescript').CustomTransformerFactory` annotated **CustomTransformerFactory** bellow

- **ProgramTransformerFactory** represents a transformer factory allowing the resulting transformer to grab a reference to the **Program** instance

  ```js
  {
    type: 'program',
    factory: (program: Program) => TransformerFactory | CustomTransformerFactory
  }
  ```

- **TypeCheckerTransformerFactory** represents a transformer factory allowing the resulting transformer to grab a reference to the **TypeChecker** instance
  ```js
  {
    type: 'typeChecker',
    factory: (typeChecker: TypeChecker) => TransformerFactory | CustomTransformerFactory
  }
  ```

```js
typescript({
  transformers: {
    before: [
      {
        // Allow the transformer to get a Program reference in it's factory
        type: 'program',
        factory: (program) => {
          return ProgramRequiringTransformerFactory(program);
        }
      },
      {
        type: 'typeChecker',
        factory: (typeChecker) => {
          // Allow the transformer to get a TypeChecker reference in it's factory
          return TypeCheckerRequiringTransformerFactory(typeChecker);
        }
      }
    ],
    after: [
      // You can use normal transformers directly
      require('custom-transformer-based-on-Context')
    ],
    afterDeclarations: [
      // Or even define in place
      function fixDeclarationFactory(context) {
        return function fixDeclaration(source) {
          function visitor(node) {
            // Do real work here

            return ts.visitEachChild(node, visitor, context);
          }

          return ts.visitEachChild(source, visitor, context);
        };
      }
    ]
  }
});
```

### `cacheDir`

Type: `String`<br>
Default: _.rollup.cache_

When compiling with `incremental` or `composite` options the plugin will
store compiled files in this folder. This allows the use of incremental
compilation.

```js
typescript({
  cacheDir: '.rollup.tscache'
});
```

### `noForceEmit`

Type: `Boolean`<br>
Default: `false`

Earlier version of `@rollup/plugin-typescript` required that the `compilerOptions` `noEmit` and `emitDeclarationOnly` both false to guarantee that source code was fed into the next plugin/output. This is no longer true. This option disables the plugin forcing the values of those options and instead defers to the values set in `tsconfig.json`.

`noForceEmit` can be very useful if you use with `@rollup/plugin-babel` and `@babel/preset-typescript`. Having `@rollup/plugin-typescript` only do typechecking / declarations with `"emitDeclarationOnly": true` while deferring to `@rollup/plugin-babel` for transpilation can dramatically reduce `rollup` build times for large projects.

### Typescript compiler options

Some of Typescript's [CompilerOptions](https://www.typescriptlang.org/docs/handbook/compiler-options.html) affect how Rollup builds files.

#### `noEmitOnError`

Type: `Boolean`<br>
Default: `false`

If a type error is detected, the Rollup build is aborted when this option is set to true.

#### `files`, `include`, `exclude`

Type: `Array[...String]`<br>
Default: `[]`

Declaration files are automatically included if they are listed in the `files` field in your `tsconfig.json` file. Source files in these fields are ignored as Rollup's configuration is used instead.

#### Ignored options

These compiler options are ignored by Rollup:

- `noEmitHelpers`, `importHelpers`: The `tslib` helper module always must be used.
- `noEmit`, `emitDeclarationOnly`: Typescript needs to emit code for the plugin to work with.
  - _Note: While this was true for early iterations of `@rollup/plugin-typescript`, it is no longer. To override this behavior, and defer to `tsconfig.json` for these options, see the [`noForceEmit`](#noForceEmit) option_
- `noResolve`: Preventing Typescript from resolving code may break compilation

### Importing CommonJS

Though it is not recommended, it is possible to configure this plugin to handle imports of CommonJS files from TypeScript. For this, you need to specify `CommonJS` as the module format and add [`@rollup/plugin-commonjs`](https://github.com/rollup/plugins/tree/master/packages/commonjs) to transpile the CommonJS output generated by TypeScript to ES Modules so that rollup can process it.

```js
// rollup.config.js
import typescript from '@rollup/plugin-typescript';
import commonjs from '@rollup/plugin-commonjs';

export default {
  input: './main.ts',
  plugins: [
    typescript({ compilerOptions: { module: 'CommonJS' } }),
    commonjs({ extensions: ['.js', '.ts'] }) // the ".ts" extension is required
  ]
};
```

Note that this will often result in less optimal output.

### Preserving JSX output

Whenever choosing to preserve JSX output to be further consumed by another transform step via `tsconfig` `compilerOptions` by setting `jsx: 'preserve'` or [overriding options](#options), please bear in mind that, by itself, this plugin won't be able to preserve JSX output, usually failing with:

```sh
[!] Error: Unexpected token (Note that you need plugins to import files that are not JavaScript)
file.tsx (1:15)
1: export default <span>Foobar</span>
                  ^
```

To prevent that, make sure to use the acorn plugin, namely `acorn-jsx`, which will make Rollup's parser acorn handle JSX tokens. (See https://rollupjs.org/guide/en/#acorninjectplugins)

After adding `acorn-jsx` plugin, your Rollup config would look like the following, correctly preserving your JSX output.

```js
import jsx from 'acorn-jsx';
import typescript from '@rollup/plugin-typescript';

export default {
  // … other options …
  acornInjectPlugins: [jsx()],
  plugins: [typescript({ compilerOptions: { jsx: 'preserve' } })]
};
```

### Faster compiling

Previous versions of this plugin used Typescript's `transpileModule` API, which is faster but does not perform typechecking and does not support cross-file features like `const enum`s and emit-less types. If you want this behaviour, you can use [@rollup/plugin-sucrase](https://github.com/rollup/plugins/tree/master/packages/sucrase) instead.

## Meta

[CONTRIBUTING](/.github/CONTRIBUTING.md)

[LICENSE (MIT)](/LICENSE)
