<div align="center">
<h1>Fork TS Checker Webpack Plugin</h1>
<p>Webpack plugin that runs TypeScript type checker on a separate process.</p>
[](https://www.npmjs.com/package/fork-ts-checker-webpack-plugin)
[](https://github.com/TypeStrong/fork-ts-checker-webpack-plugin/actions?query=branch%3Amain+event%3Apush)
[](https://npmjs.org/package/fork-ts-checker-webpack-plugin)
[](http://commitizen.github.io/cz-cli/)
[](https://github.com/prettier/prettier)
[](https://github.com/semantic-release/semantic-release)
</div>
## Features
* Speeds up [TypeScript](https://github.com/Microsoft/TypeScript) type checking and [ESLint](https://eslint.org/) linting (by moving each to a separate process) 🏎
* Supports modern TypeScript features like [project references](https://www.typescriptlang.org/docs/handbook/project-references.html) and [incremental mode](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-4.html#faster-subsequent-builds-with-the---incremental-flag) ✨
* Supports [Vue Single File Component](https://vuejs.org/v2/guide/single-file-components.html) ✅
* Displays nice error messages with the [code frame](https://babeljs.io/docs/en/next/babel-code-frame.html) formatter 🌈
## Installation
This plugin requires minimum **Node.js 10**, **Webpack 4**, **TypeScript 2.7** and optionally **ESLint 6**
* If you depend on **Webpack 2**, **Webpack 3**, or **TSLint 4**, please use [version 3](https://github.com/TypeStrong/fork-ts-checker-webpack-plugin/tree/v3.1.1) of the plugin.
* If you depend on **TypeScript >= 2.1** and **< 2.7** or you can't update to **Node 10**, please use [version 4](https://github.com/TypeStrong/fork-ts-checker-webpack-plugin/tree/v4.1.4) of the plugin.
```sh
# with npm
npm install --save-dev fork-ts-checker-webpack-plugin
# with yarn
yarn add --dev fork-ts-checker-webpack-plugin
```
The minimal webpack config (with [ts-loader](https://github.com/TypeStrong/ts-loader))
```js
// webpack.config.js
const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');
module.exports = {
context: __dirname, // to automatically find tsconfig.json
entry: './src/index.ts',
resolve: {
extensions: [".ts", ".tsx", ".js"],
},
module: {
rules: [
{
test: /\.tsx?$/,
loader: 'ts-loader',
exclude: /node_modules/,
options: {
// disable type checker - we will use it in fork plugin
transpileOnly: true
}
}
]
},
plugins: [new ForkTsCheckerWebpackPlugin()]
};
```
> Examples how to configure it with [babel-loader](https://github.com/babel/babel-loader), [ts-loader](https://github.com/TypeStrong/ts-loader),
> [eslint](https://github.com/eslint/eslint) and [Visual Studio Code](https://code.visualstudio.com/) are in the
> [**examples**](./examples) directory.
## Modules resolution
It's very important to be aware that **this plugin uses [TypeScript](https://github.com/Microsoft/TypeScript)'s, not
[webpack](https://github.com/webpack/webpack)'s modules resolution**. It means that you have to setup `tsconfig.json` correctly.
> It's because of the performance - with TypeScript's module resolution we don't have to wait for webpack to compile files.
>
> To debug TypeScript's modules resolution, you can use `tsc --traceResolution` command.
## ESLint
If you'd like to use ESLint with the plugin, ensure you have the relevant dependencies installed:
```sh
# with npm
npm install --save-dev eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin
# with yarn
yarn add --dev eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin
```
Then set up ESLint in the plugin. This is the minimal configuration:
```js
// webpack.config.js
const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');
module.exports = {
// ...the webpack configuration
plugins: [
new ForkTsCheckerWebpackPlugin({
eslint: {
files: './src/**/*.{ts,tsx,js,jsx}' // required - same as command `eslint ./src/**/*.{ts,tsx,js,jsx} --ext .ts,.tsx,.js,.jsx`
}
})
]
};
```
You should also have an ESLint configuration file in your root project directory.
Here is a sample `.eslintrc.js` configuration for a TypeScript project:
```js
module.exports = {
parser: '@typescript-eslint/parser',
parserOptions: {
ecmaVersion: 2018,
sourceType: 'module',
},
extends: [
'plugin:@typescript-eslint/recommended'
],
rules: {
// place to specify ESLint rules - can be used to overwrite rules specified from the extended configs
// e.g. "@typescript-eslint/explicit-function-return-type": "off",
}
};
```
There's a [good explanation on setting up TypeScript ESLint support by Robert Cooper](https://dev.to/robertcoopercode/using-eslint-and-prettier-in-a-typescript-project-53jb).
## Options
This plugin uses [`cosmiconfig`](https://github.com/davidtheclark/cosmiconfig). This means that besides the plugin constructor,
you can place your configuration in the:
* `"fork-ts-checker"` field in the `package.json`
* `.fork-ts-checkerrc` file in JSON or YAML format
* `fork-ts-checker.config.js` file exporting a JS object
Options passed to the plugin constructor will overwrite options from the cosmiconfig (using [deepmerge](https://github.com/TehShrike/deepmerge)).
| Name | Type | Default value | Description |
| ----------------- | ---------------------------------- | ------------------------------------------------------------------ | ----------- |
| `async` | `boolean` | `compiler.options.mode === 'development'` | If `true`, reports issues **after** webpack's compilation is done. Thanks to that it doesn't block the compilation. Used only in the `watch` mode. |
| `typescript` | `object` or `boolean` | `true` | If a `boolean`, it enables/disables TypeScript checker. If an `object`, see [TypeScript options](#typescript-options). |
| `eslint` | `object` | `undefined` | If `undefined`, it disables ESLint linter. If an `object`, see [ESLint options](#eslint-options). |
| `issue` | `object` | `{}` | See [Issues options](#issues-options). |
| `formatter` | `string` or `object` or `function` | `codeframe` | Available formatters are `basic`, `codeframe` and a custom `function`. To [configure](https://babeljs.io/docs/en/babel-code-frame#options) `codeframe` formatter, pass object: `{ type: 'codeframe', options: { <coderame options> } }`. |
| `logger` | `object` | `{ infrastructure: 'silent', issues: 'console', devServer: true }` | Available loggers are `silent`, `console`, and `webpack-infrastructure`. Infrastructure logger prints additional information, issue logger prints `issues` in the `async` mode. If `devServer` is set to `false`, errors will not be reported to Webpack Dev Server. |
### TypeScript options
Options for the TypeScript checker (`typescript` option object).
| Name | Type | Default value | Description |
| -------------------- | --------- | -------------------------------------------------------------------------------------------------------------- | ----------- |
| `enabled` | `boolean` | `true` | If `true`, it enables TypeScript checker. |
| `memoryLimit` | `number` | `2048` | Memory limit for the checker process in MB. If the process exits with the allocation failed error, try to increase this number. |
| `configFile` | `string` | `'tsconfig.json'` | Path to the `tsconfig.json` file (path relative to the `compiler.options.context` or absolute path) |
| `configOverwrite` | `object` | `{ compilerOptions: { skipLibCheck: true, sourceMap: false, inlineSourceMap: false, declarationMap: false } }` | This configuration will overwrite configuration from the `tsconfig.json` file. Supported fields are: `extends`, `compilerOptions`, `include`, `exclude`, `files`, and `references`. |
| `context` | `string` | `dirname(configuration.configFile)` | The base path for finding files specified in the `tsconfig.json`. Same as the `context` option from the [ts-loader](https://github.com/TypeStrong/ts-loader#context). Useful if you want to keep your `tsconfig.json` in an external package. Keep in mind that **not** having a `tsconfig.json` in your project root can cause different behaviour between `fork-ts-checker-webpack-plugin` and `tsc`. When using editors like `VS Code` it is advised to add a `tsconfig.json` file to the root of the project and extend the config file referenced in option `configFile`. |
| `build` | `boolean` | `false` | The equivalent of the `--build` flag for the `tsc` command. |
| `mode` | `'readonly'` or `'write-tsbuildinfo'` or `'write-dts'` or `'write-references'` | `'write-tsbuildinfo'` | If you use the `babel-loader`, it's recommended to use `write-references` mode to improve initial compilation time. If you use `ts-loader`, it's recommended to use `write-tsbuildinfo` mode to not overwrite files emitted by the `ts-loader`. If you use `ts-loader` with `transpileOnly` flag set to `true`, use `'write-dts` to emit the type definition files. |
| `diagnosticOptions` | `object` | `{ syntactic: false, semantic: true, declaration: false, global: false }` | Settings to select which diagnostics do we want to perform. |
| `extensions` | `object` | `{}` | See [TypeScript extensions options](#typescript-extensions-options). |
| `profile` | `boolean` | `false` | Measures and prints timings related to the TypeScript performance. |
| `typescriptPath` | `string` | `require.resolve('typescript')` | If supplied this is a custom path where TypeScript can be found. |
#### TypeScript extensions options
Options for the TypeScript checker extensions (`typescript.extensions` option object).
| Name | Type | Default value | Description |
| -------------------- | --------------------- | ------------------------- | ----------- |
| `vue` | `object` or `boolean` | `false` | If `true`, it enables Vue [Single File Component](https://vuejs.org/v2/guide/single-file-components.html) support. |
| `vue.enabled` | `boolean` | `false` | Same as the `vue` option |
| `vue.compiler` | `string` | `'vue-template-compiler'` | The package name of the compiler that will be used to parse `.vue` files. You can use `'nativescript-vue-template-compiler'` if you use [nativescript-vue](https://github.com/nativescript-vue/nativescript-vue) |
### ESLint options
Options for the ESLint linter (`eslint` option object).
| Name | Type | Default value | Description |
| -------------------- | ---------------------- | ------------------------- | ----------- |
| `enabled` | `boolean` | `false` | If `true`, it enables ESLint linter. If you set the `files` option, it will be `true` by default. |
| `files` | `string` or `string[]` | This value is required | One or more [glob patterns](https://en.wikipedia.org/wiki/Glob_(programming)) to the files that should be linted. Works the same as the `eslint` command. |
| `memoryLimit` | `number` | `2048` | Memory limit for the linter process in MB. If the process exits with the allocation failed error, try to increase this number. |
| `options` | `object` | `{}` | [Options](https://eslint.org/docs/developer-guide/nodejs-api#cliengine) that can be used to initialize ESLint. |
### Issues options
Options for the issues filtering (`issue` option object).
I could write some plain text explanation of these options but I think code will explain it better:
```typescript
interface Issue {
origin: 'typescript' | 'eslint';
severity: 'error' | 'warning';
code: string;
file?: string;
}
type IssueMatch = Partial<Issue>; // file field supports glob matching
type IssuePredicate = (issue: Issue) => boolean;
type IssueFilter = IssueMatch | IssuePredicate | (IssueMatch | IssuePredicate)[];
```
| Name | Type | Default value | Description |
| --------- | ------------- | ------------- | ----------- |
| `include` | `IssueFilter` | `undefined` | If `object`, defines issue properties that should be [matched](./src/issue/IssueMatch.ts). If `function`, acts as a predicate where `issue` is an argument. |
| `exclude` | `IssueFilter` | `undefined` | Same as `include` but issues that match this predicate will be excluded. |
<details>
<summary>Expand example</summary>
Include issues from the `src` directory, exclude eslint issues from `.spec.ts` files:
```js
module.exports = {
// ...the webpack configuration
plugins: [
new ForkTsCheckerWebpackPlugin({
issue: {
include: [
{ file: '**/src/**/*' }
],
exclude: [
{ origin: 'eslint', file: '**/*.spec.ts' }
]
}
})
]
};
```
</details>
## Vue.js
⚠️ There are additional **constraints** regarding Vue.js Single File Component support: ⚠️
* It requires **TypeScript >= 3.8.0** (it's a limitation of the `transpileOnly` mode from `ts-loader`)
* It doesn't work with the `build` mode (project references)
To enable Vue.js support, follow these steps:
<details>
<summary>Expand Vue.js set up instruction</summary>
1. Ensure you have all required packages installed:
```sh
# with npm
npm install --save vue vue-class-component
npm install --save-dev vue-loader ts-loader css-loader vue-template-compiler
# with yarn
yarn add vue vue-class-component
yarn add --dev vue-loader ts-loader css-loader vue-template-compiler
```
2. Add `tsconfig.json` configuration:
```json
{
"compilerOptions": {
"experimentalDecorators": true,
"jsx": "preserve",
"target": "ES5",
"lib": ["ES6", "DOM"],
"baseUrl": ".",
"paths": {
"@/*": ["src/*"],
"~/*": ["src/*"]
},
"sourceMap": true,
"importsNotUsedAsValues": "preserve"
},
"include": [
"src/**/*.ts",
"src/**/*.vue"
],
"exclude": [
"node_modules"
]
}
```
3. Add `webpack.config.js` configuration:
```js
const path = require('path');
const VueLoaderPlugin = require('vue-loader/lib/plugin');
const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');
module.exports = {
entry: './src/index.ts',
output: {
filename: 'index.js',
path: path.resolve(__dirname, 'dist'),
},
module: {
rules: [
{
test: /\.vue$/,
loader: 'vue-loader'
},
{
test: /\.ts$/,
loader: 'ts-loader',
exclude: /node_modules/,
options: {
appendTsSuffixTo: [/\.vue$/],
transpileOnly: true
}
},
{
test: /\.css$/,
loader: 'css-loader'
},
],
},
resolve: {
extensions: ['.ts', '.js', '.vue', '.json'],
alias: {
'@': path.resolve(__dirname, './src'),
'~': path.resolve(__dirname, './src'),
}
},
plugins: [
new VueLoaderPlugin(),
new ForkTsCheckerWebpackPlugin({
typescript: {
extensions: {
vue: true
}
}
})
]
};
```
4. Add `src/types/vue.d.ts` file to shim `.vue` modules:
```typescript
declare module "*.vue" {
import Vue from "vue";
export default Vue;
}
```
5. If you are working in VSCode, you can get the [Vetur](https://marketplace.visualstudio.com/items?itemName=octref.vetur) extension to complete the developer workflow.
</details>
## Plugin hooks
This plugin provides some custom webpack hooks:
| Hook key | Type | Params | Description |
| ---------- | -------------------------- | --------------------- | ----------- |
| `start` | `AsyncSeriesWaterfallHook` | `change, compilation` | Starts issues checking for a compilation. It's an async waterfall hook, so you can modify the list of changed and removed files or delay the start of the service. |
| `waiting` | `SyncHook` | `compilation` | Waiting for the issues checking. |
| `canceled` | `SyncHook` | `compilation` | Issues checking for the compilation has been canceled. |
| `error` | `SyncHook` | `compilation` | An error occurred during issues checking. |
| `issues` | `SyncWaterfallHook` | `issues, compilation` | Issues have been received and will be reported. It's a waterfall hook, so you can modify the list of received issues. |
To access plugin hooks and tap into the event, we need to use the `getCompilerHooks` static method.
When we call this method with a [webpack compiler instance](https://webpack.js.org/api/node/), it returns the object with
[tapable](https://github.com/webpack/tapable) hooks where you can pass in your callbacks.
```js
// ./src/webpack/MyWebpackPlugin.js
const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');
class MyWebpackPlugin {
apply(compiler) {
const hooks = ForkTsCheckerWebpackPlugin.getCompilerHooks(compiler);
// log some message on waiting
hooks.waiting.tap('MyPlugin', () => {
console.log('waiting for issues');
});
// don't show warnings
hooks.issues.tap('MyPlugin', (issues) =>
issues.filter((issue) => issue.severity === 'error')
);
}
}
module.exports = MyWebpackPlugin;
// webpack.config.js
const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');
const MyWebpackPlugin = require('./src/webpack/MyWebpackPlugin');
module.exports = {
/* ... */
plugins: [
new ForkTsCheckerWebpackPlugin(),
new MyWebpackPlugin()
]
};
```
## Typings
To use the plugin typings, you have to install `@types/webpack`. It's not included by default to not collide with your
existing typings (`@types/webpack` imports `@types/node`). [It's an old TypeScript issue](https://github.com/microsoft/TypeScript/issues/18588),
the alternative is to set `skipLibCheck: true` in the `compilerOptions` 😉
```sh
# with npm
npm install --save-dev @types/webpack
# with yarn
yarn add --dev @types/webpack
```
## Profiling types resolution
Starting from TypeScript 4.1.0, you can profile long type checks by
setting "generateTrace" compiler option. This is an instruction from [microsoft/TypeScript#40063](https://github.com/microsoft/TypeScript/pull/40063):
1. Set "generateTrace": "{folderName}" in your `tsconfig.json`
2. Look in the resulting folder. If you used build mode, there will be a `legend.json` telling you what went where.
Otherwise, there will be `trace.json` file and `types.json` files.
3. Navigate to [edge://tracing](edge://tracing) or [chrome://tracing](chrome://tracing) and load `trace.json`
4. Expand Process 1 with the little triangle in the left sidebar
5. Click on different blocks to see their payloads in the bottom pane
6. Open `types.json` in an editor
7. When you see a type ID in the tracing output, go-to-line {id} to find data about that type
## Related projects
* [`ts-loader`](https://github.com/TypeStrong/ts-loader) - TypeScript loader for webpack.
* [`babel-loader`](https://github.com/babel/babel-loader) - Alternative TypeScript loader for webpack.
* [`fork-ts-checker-notifier-webpack-plugin`](https://github.com/johnnyreilly/fork-ts-checker-notifier-webpack-plugin) - Notifies about build status using system notifications (similar to the [webpack-notifier](https://github.com/Turbo87/webpack-notifier)).
## Credits
This plugin was created in [Realytics](https://www.realytics.io/) in 2017. Thank you for supporting Open Source.
## License
MIT License