TypeScript Function Decorator Support

A TypeScript transformer that enables function decorators to transform function calls at compile time. This package provides a powerful way to modify function behavior through decorators while maintaining type safety.

Features

• 🔄 Function Transformation: Transform function calls at compile time
• 🔒 Type Safety: Full TypeScript support with proper type inference
• 🚀 Zero Runtime Overhead: Transformations happen at compile time
• 🛠️ Customizable: Create your own decorators with custom transformation logic

Installation

npm install -D ts-function-decorator ts-patch

Usage

1. Configure ts-patch to enable the transformer.

2. Add the transformer to your tsconfig.json:

{
  "compilerOptions": {
    "plugins": [
      {
        "transform": "ts-function-decorator",
        "transformProgram": true
      }
    ]
  }
}

2. Use Decorators

// Create a decorator
const log = function (fn: Function) {
  return function (...args: any[]) {
    console.log('Function called with args:', args);
    return fn.apply(this, args);
  };
};

// Use the decorator
@log
function example(arg: string): string {
  return arg;
}

The decorator will transform the function at compile time to:

function example(arg: string): string {
  return log((arg: string) => {
    return arg;
  })(arg);
}

Caveats

This transformer modifies the AST of the program before it is consumed by the compiler/language service. Therefore, if you include this transformer in your tsconfig.json, it may cause issues with syntax highlighting in your editor. To fix this, it is best to use one tsconfig.json for the project (that is used by your editor), and a tsconfig.build.json for the build process.

tsconfig.json

{
  ...
  "compilerOptions": {
    ...
    "plugins": [
      {
        "name": "ts-function-decorator-ls"
      }
    ]
  }
}

This will be used automatically by your editor and enable decorators in your editor.

tsconfig.build.json

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "plugins": [
      {
        "transform": "ts-function-decorator",
        "transformProgram": true
      }
    ]
  }
}

Use this via tsc -p tsconfig.build.json to build your project.

License

Apache-2.0