TypeScript loader for webpack

This is the typescript loader for webpack.

Getting Started

Examples

We have a number of example setups to accomodate different workflows. From "vanilla" ts-loader, to using ts-loader in combination with babel for transpilation, happypack for faster builds and fork-ts-checker-webpack-plugin for performing type checking in a separate process. Our examples can be found here.

Babel

ts-loader works very well in combination with babel and babel-loader. There is an example of this in the official TypeScript Samples. Alternatively take a look at our own example.

Faster Builds

As your project becomes bigger and bigger, compilation time increases linearly. It's because typescript's semantic checker has to inspect all files on every rebuild. The simple solution is to disable it by using the transpileOnly: true option, but doing so leaves you without type checking.

You probably don't want to give up type checking; that's rather the point of TypeScript. So what you can do is use the fork-ts-checker-webpack-plugin. It runs the type checker on a separate process, so your build remains fast thanks to transpileOnly: true but you still have the type checking. Also, the plugin has several optimizations to make incremental type checking faster (AST cache, multiple workers).

If you'd like to see a simple setup take a look at our simple example. For a more complex setup take a look at our more involved example.

If you'd like to make things even faster still (I know, right?) then you might want to consider using ts-loader with happypack which speeds builds by parallelising work. (This should be used in combination with fork-ts-checker-webpack-plugin for typechecking.) If you'd like to see a simple setup take a look at our simple example. For a more complex setup take a look at our more involved example.

Installation

npm install ts-loader

You will also need to install TypeScript if you have not already.

npm install typescript

Running

Use webpack like normal, including webpack --watch and webpack-dev-server, or through another build system using the Node.js API.

Configuration

Create or update webpack.config.js like so:

module.exports = {
  entry: './app.ts',
  output: {
    filename: 'bundle.js'
  },
  resolve: {
    // Add `.ts` and `.tsx` as a resolvable extension.
    extensions: ['.ts', '.tsx', '.js'] // note if using webpack 1 you'd also need a '' in the array as well
  },
  module: {
    loaders: [ // loaders will work with webpack 1 or 2; but will be renamed "rules" in future
      // all files with a `.ts` or `.tsx` extension will be handled by `ts-loader`
      { test: /\.tsx?$/, loader: 'ts-loader' }
    ]
  }
}

Add a tsconfig.json file. (The one below is super simple; but you can tweak this to your hearts desire)
```
{
  "compilerOptions": {
    "sourceMap": true
  }
}
```

The tsconfig.json file controls TypeScript-related options so that your IDE, the tsc command, and this loader all share the same options. For ts-loader to produce sourcemaps, you will need to set the tsconfig.json option as "sourceMap": true.

Code Splitting and Loading Other Resources

Loading css and other resources is possible but you will need to make sure that you have defined the require function in a declaration file.

declare var require: {
    <T>(path: string): T;
    (paths: string[], callback: (...modules: any[]) => void): void;
    ensure: (paths: string[], callback: (require: <T>(path: string) => T) => void) => void;
};

Then you can simply require assets or chunks per the webpack documentation.

require('!style!css!./style.css');

The same basic process is required for code splitting. In this case, you import modules you need but you don't directly use them. Instead you require them at split points. See this example and this example for more details.

TypeScript 2.4 provides support for ECMAScript's new import() calls. These calls import a module and return a promise to that module. This is also supported in webpack - details on usage can be found here. Happy code splitting!

Compatibility

TypeScript / Webpack

ts-loader supports the latest and greatest version of TypeScript right back to v1.6.

ts-loader supports webpack 2. It may well still work with webpack 1 but it does not officially support webpack 1 any longer. Our continuous integration test suites run against webpack 2; not webpack 1.

A full test suite runs each night (and on each pull request). It runs both on Linux and Windows, testing ts-loader against each major release of TypeScript from the latest right back to 1.6. The test suite also runs against TypeScript@next (because we want to use it as much as you do).

If you become aware of issues not caught by the test suite then please let us know. Better yet, write a test and submit it in a PR!

Failing the build on TypeScript compilation error

When the build fails (i.e. at least one typescript compile error occured), ts-loader does not propagate the build failure to webpack. The upshot of this is you can fail to notice an erroring build. This is inconvenient; particularly in continuous integration scenarios. If you want to ensure that the build failure is propogated it is advised that you make use of the webpack-fail-plugin. This plugin that will make the process return status code 1 when it finishes with errors in single-run mode. Et voilà! Build failure.

For more background have a read of this issue.

Options

There are two types of options: TypeScript options (aka "compiler options") and loader options. TypeScript options should be set using a tsconfig.json file. Loader options can be set either using a query when specifying the loader or through the options property in the webpack configuration:

module.exports = {
  ...
  module: {
    rules: [
      { 
        test: /\.tsx?$/, 
        loader: 'ts-loader', 
        options: {
          transpileOnly: true
        } 
      }
    ]
  }
}

Alternatively this can be configured using a query:

module.exports = {
  ...
  module: {
    loaders: [
      // specify option using query
      { 
        test: /\.tsx?$/,
        loader: 'ts-loader?' + JSON.stringify({
          transpileOnly: true
        }) }
    ]
  }
}

For a full breakdown of the power of query syntax have a read of this.

Loader Options

transpileOnly (boolean) (default=false)

If you want to speed up compilation significantly you can set this flag. However, many of the benefits you get from static type checking between different dependencies in your application will be lost. You should also set the isolatedModules TypeScript option if you plan to ever make use of this.

happyPackMode (boolean) (default=false)

Enables happypack compatibility mode. This implicitly sets *transpileOnly* to true. WARNING! Some errors will be silently ignored in happypack mode (tsconfig.json parsing errors, dependency resolution errors, etc.).

It's advisable to use happypack alongside fork-ts-checker-webpack-plugin to get full type checking again. To see what this looks like in practice then either take a look at our simple example. For a more complex setup take a look at our more involved example.

getCustomTransformers ( () => { before?: TransformerFactory[]; after?: TransformerFactory[]; } )

Provide custom transformers - only compatible with TypeScript 2.3+ (and 2.4 if using transpileOnly mode). For example usage take a look at typescript-plugin-styled-components or our test.

logInfoToStdOut (boolean) (default=false)

This is important if you read from stdout or stderr and for proper error handling. The default value ensures that you can read from stdout e.g. via pipes or you use webpack -j to generate json output.

logLevel (string) (default=info)

Can be info, warn or error which limits the log output to the specified log level. Beware of the fact that errors are written to stderr and everything else is written to stderr (or stdout if logInfoToStdOut is true).

silent (boolean) (default=false)

If true, no console.log messages will be emitted. Note that most error messages are emitted via webpack which is not affected by this flag.

ignoreDiagnostics (number[]) (default=[])

You can squelch certain TypeScript errors by specifying an array of diagnostic codes to ignore.

compiler (string) (default='typescript')

Allows use of TypeScript compilers other than the official one. Should be set to the NPM name of the compiler, eg ntypescript.

configFileName (string) (default='tsconfig.json')

Allows you to specify a custom configuration file.

visualStudioErrorFormat (boolean) (default=false)

If true, the TypeScript compiler output for an error or a warning, e.g. (3,14): error TS4711: you did something very wrong, in file myFile will instead be myFile(3,14): error TS4711: you did something very wrong (notice the file name at the beginning). This way Visual Studio will interpret this line and show any errors or warnings in the error list. This enables navigation to the file/line/column through double click.

compilerOptions (object) (default={})

Allows overriding TypeScript options. Should be specified in the same format as you would do for the compilerOptions property in tsconfig.json.

instance (string)

Advanced option to force files to go through different instances of the TypeScript compiler. Can be used to force segregation between different parts of your code.

entryFileIsJs (boolean) (default=false)

To be used in concert with the allowJs compiler option. If your entry file is JS then you'll need to set this option to true. Please note that this is rather unusual and will generally not be necessary when using allowJs.

appendTsSuffixTo (RegExp[]) (default=[])

A list of regular expressions to be matched against filename. If filename matches one of the regular expressions, a .ts suffix will be appended to that filename.

This is useful for *.vue file format for now. (Probably will benefit from the new single file format in the future.)

Example:

webpack.config.js:

module.exports = {
    entry: './index.vue',
    output: { filename: 'bundle.js' },
    resolve: {
        extensions: ['.ts', '.vue']
    },
    module: {
        rules: [
            { test: /\.vue$/, loader: 'vue-loader' },
            { test: /\.ts$/, loader: 'ts-loader', options: { appendTsSuffixTo: [/\.vue$/] } }
        ]
    } 
}

index.vue

<template><p>hello {{msg}}</p></template>
<script lang="ts">
export default {
  data(): Object {
    return {
      msg: "world"
    }
  },
}
</script>

`LoaderOptionsPlugin`

There's a known "gotcha" if you are using webpack 2 with the LoaderOptionsPlugin. If you are faced with the Cannot read property 'unsafeCache' of undefined error then you probably need to supply a resolve object as below: (Thanks @jeffijoe!)

new LoaderOptionsPlugin({		
  debug: false,		
  options: {		
    resolve: {
      extensions: ['.ts', '.tsx', '.js']
    }	
  }		
})

It's worth noting that use of the LoaderOptionsPlugin is only supposed to be a stopgap measure. You may want to look at removing it entirely.

Contributing

This is your TypeScript loader! We want you to help make it even better. Please feel free to contribute; see the contributor's guide to get started.

License

MIT License

schmuli / ts-loader