TypeScript Closure Compiler

This patches the TypeScript compiler to generate JSDoc annotations ready for Google Closure Compiler. A demo is available online at http://sagifogel.github.io/typescript-closure-compiler/. The current version is compatible with TypeScript 1.8.10. For the purposes of clarity each npm package that will be released will match TypeScript`s major and minor version. For example each version of typescript-closure-compiler that is compatible with TypeScript 1.7.5 will be constructed as 1.7.x and each version that is compatible with TypeScript 1.8.10 will be constructed as 1.8.x.

Installing

For the latest stable version:

npm install -g typescript-closure-compiler

If you work with a specific version of TypeScript (for instance 1.7.5), Then you need to install it globally using the @{version} after the typescript-closure-compiler name:

npm install -g [email protected]

Usage

The patched version of the TypeScript compiler is available as tscc after installing globally with npm install -g typescript-closure-compiler. Substitute tsc with tscc in your build script. Note that the --module flag is supported only for the compilation phase (you can write your code using any preferred module system), it won't be present in the output files since the intent is to compile and optimize all code into one big bundle. Also the output of the tscc will transpile into ECMAScript 5

tscc app.ts

Using the gulp task

tscc is a command line compiler much like TypeScript`s tsc file. You can also choose to compile your code using a gulp plugin for typescript-closure-compiler

Additional options

The patched compiler provides couple of additional options that help you to control the output of the closure compiler library.

Export symbols to the global scope

Exporting types to the global scope is done using two additional options. --entry and --exportAs. Both options should be explicitly set in order for this feature to work properly.

entry - main file that contains all exported types. exportAs - the name of the main symbol that will be exported to the global scope.

tscc app.ts --module commonjs --entry app.ts --exportAs App

Declaring Extern symbols

If you use third party libraries in your code and you don't want Closure Compiler to rename its symbols, you need to declare some externs. Declaring externs is done using additional option --externs. All you need to do is specify the list of extern files after the externs option.

tscc app.ts --module commonjs --externs externs/app-extern.d.ts...

You can also specify the files in a tsconfig.json file. use the project option to locate the tsconfig.json file:

tscc --project [project specific directory]

and declare the options in the tsconfig.json file:

{
  "compilerOptions": {
    "module": "commonjs"
  },
  "files": [
    "app.ts"
  ],
  "externs": [
    "externs/app-externs.d.ts"
  ]
}

you can also use the externsOutFile option in order to emit all extern files to a single file.

tscc app.ts --module commonjs --externs externs/app-extern.d.ts --externsOutFile externs.js

or declaring it in the config.ts file:

{
  "compilerOptions": {
    "module": "commonjs",
    "externsOutFile": "externs.js"
  },
  "files": [
    "app.ts"
  ],
  "externs": [
    "externs/app-externs.d.ts"
  ]
}

One side enums

By default typescript-closure-compiler emits bi-directional enums, which means that the key could also be resolved using the value.

enum EventType {
    mouseup = 0,
    mousedown = 1
}

will be translated to:

var EventType = {
    mouseup: 0,
    mousedown: 1,
    "0": "mouseup",
    "1": "mousedown"
};

In order to resolve the key from the value you can write:

console.log(EventType[0]); 

"mouseup" will be printed

You can use the emitOneSideEnums property to override this behaviour and to just emit one side enums:

tscc app.ts --module commonjs --emitOneSideEnums

Now for the same enum the emitted code will be:

var EventType = {
    mouseup: 0,
    mousedown: 1
};

experimentalDecorators and ignoreDecoratorsWarning

In case you annotate your class/methods/params with decorators without enabling the experimentalDecorators option, TypeScript will emit all the code that enables this feature, but will output a warning message to enable this option.

function f() {
    console.log("f(): evaluated");
    return function (target, propertyKey: string, descriptor: PropertyDescriptor) {
        console.log("f(): called");
    } 
}

class C {
    @f()
    method() {}
}

The output will be:

Experimental support for decorators is a feature that is subject to change in a future release. Set the 'experimentalDecorators' option to remove this warning.

typescript-closure-compiler changes this behaviour and omits all decorators relevant code when the experimentalDecorators is not enabled, thus ensuring that the generated javascript will not include unnecessary code. In addition typescript-closure-compiler enables you to use the ignoreDecoratorsWarning option in order to ignore the warning message. These two options enables you to write your code once using decorations, but to omit the decorations related code using configuration, much like choosing the verbosity of a logger using configuration. A reasonable scenario would be to decorate your class/methods/params with decorators for debug purposes but to omit this code in the final release. All you have to do is create two tsconfig.json files one for debug and one for release. The release file should include the ignoreDecoratorsWarning. The debug file should include the experimentalDecorators.

release

{
  "compilerOptions": {
    "ignoreDecoratorsWarning": true
  }
  "files": [
  ]
}

debug

{
  "compilerOptions": {
    "experimentalDecorators": true
  }
  "files": [
  ]
}

Usage Examples

See an example of typescript-closure-compiler using gulp-typescript-closure-compiler plugin in the TSFunq project.

Building

The build tool that was chosen for this project is Jake, for compatibility reasons with TypeScript`s build system.

git clone https://github.com/sagifogel/typescript-closure-compiler.git

Install Jake tools and the dev dependencies of typescript-closure-compiler

npm install -g jake
npm install

Clone the submodule

cd .\TypeScript
git submodule update --init

Navigate to the TypeScript folder and install its dependencies

npm install

Return to the folder of typescript-closure-compiler and execute the build

jake build

License

Like the TypeScript compiler itself, this code is licensed under the Apache License 2.0.