ts-transformer-export-default-name

This is a TypeScript AST transformer ^[1] that assigns a name to each arrow/anonymous function and class exported as default (e.g. export default () ⇒ 42). The name is derived from the name of the source file or its directory, in the case of index file.

This transformer does basically the same as babel-plugin-transform-export-default-name but it’s implemented for the TypeScript compiler. See README of the aforesaid Babel plugin for the explanation why is this useful.

Examples

Arrow Function

forty-two.ts:

export default () => 42

This will be transformed to:

forty-two.js:

const fortyTwo = () => 42;
export default fortyTwo;

Anonymous Function Declaration

forty-two.ts:

export default function () {
  return 42
}

This will be transformed to:

forty-two.js:

export default function fortyTwo() {
  return 42;
}

Anonymous Class Declaration

forty-two.ts:

export default class {
  get answer () { return 42 }
}

This will be transformed to:

forty-two.js:

export default class FortyTwo {
  get answer() { return 42; }
}

How to Use

Add ts-transformer-export-default-name package to your project as a development dependency and register it as a custom transformer.

Unfortunately, TypeScript itself does not currently provide any easy way to use custom transformers (see Microsoft/TypeScript#14419). Fortunately, there are few solutions.

TTypescript

If you don’t use any bundler such as Rollup or webpack, TTypescript is the way to go. It provides wrappers ttsc and ttserver for the tsc and tsserver commands that add support for custom transformers. All you have to do is to use these wrappers instead of the original commands and define the transformer in your tsconfig.json:

tsconfig.json:

{
  "compilerOptions": {
    // ...
    "plugins": [
      { "transform": "ts-transformer-export-default-name" }
    ]
  },
  // ...
}

Rollup (with rollup-plugin-typescript2)

rollup.config.js:

import typescript from 'rollup-plugin-typescript2'
import exportDefaultNameTransformer from 'ts-transformer-export-default-name'

export default {
  // ...
  plugins: [
    typescript({
      transformers: [
        (service) => ({
          before: [ exportDefaultNameTransformer(service.getProgram()) ],
          after: [],
        }),
      ],
    }),
  ],
}

Webpack (with ts-loader or awesome-typescript-loader)

webpack.config.js:

const exportDefaultNameTransformer = require('ts-transformer-export-default-name').default

module.exports = {
  // ...
  module: {
    rules: [
      {
        test: /\.ts$/,
        loader: 'ts-loader', // or 'awesome-typescript-loader',
        options: {
          getCustomTransformers: (program) => ({
            before: [
              exportDefaultNameTransformer(program),
            ],
          }),
        },
      },
    ],
  },
}

Development

System Requirements

• NodeJS 10.13+

• Pandoc and Asciidoctor (used only for converting README.adoc to Markdown for npmjs)

Used Tools

• TypeScript the language

• yarn for dependencies management and building

• ESLint for linting JS/TypeScript code

• tape for testing

• Istanbul for tracking test coverage

How to Start

1. Clone this repository:

   git clone https://github.com/jirutka/ts-transformer-export-default-name.git
   cd ts-transformer-export-default-name

2. Install Yarn (if you don’t have it already):

   npm install -g yarn

3. Install all JS dependencies:

   yarn install

4. Build the project:

   yarn build

5. Run tests and generate code coverage:

   yarn test

6. Run linter:

   yarn lint

Visual Studio Code

If you use Visual Studio Code, you may find the following extensions useful:

• Coverage Gutters

• EditorConfig for VS Code

• ESLint

• yarn

Credits

• This project is highly inspired by babel-plugin-transform-export-default-name.

License

This project is licensed under MIT License. For the full text of the license, see the LICENSE file.

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1. If you’ve never heard about TypeScript transformers, I can recommend this blog post to dive into the topic.