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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 (v8.0.0+) and Rollup v1.20.0+. Due to the use of `tslib` to inject helpers, this plugin requires at least [TypeScript 2.1](https://github.com/Microsoft/TypeScript/wiki/Roadmap#21-december-2016). See also [here](https://blog.mariusschulz.com/2016/12/16/typescript-2-1-external-helpers-library#the-importhelpers-flag-and-tslib).

## 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/rollup-plugin-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({lib: ["es5", "es6", "dom"], target: "es5"})
  ]
}
```

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

### `exclude`

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

A [minimatch pattern](https://github.com/isaacs/minimatch), 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 [minimatch pattern](https://github.com/isaacs/minimatch), 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.

### `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')
});
```

### 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: `true`

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.
- `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` 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({ 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({ 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)
