Clutz - Closure to TypeScript Declarations (`.d.ts`) generator.

Clutz has been archived, which means the repository is in a read-only state. Clutz will not receive updates, and issues and pull requests will be locked.

We don’t believe that Clutz satisfies the needs of the open-source community. The use-case it was designed for is very limited, and only works with the full stack of Google TypeScript tooling. Clutz has also proven to be difficult to use: due to the tight integration with Closure Compiler it is only usable when building the latest versions of each. Additionally, many have tried to use it as a general JavaScript to TypeScript migrator and it fails at this.

We have updated the default branch to be buildable so that existing users may continue using Clutz as-is.

This project uses the Closure Compiler to parse Closure-style JSDoc type annotations from ES5/ES2015 code, and generates a suitable TypeScript type definition file (.d.ts) for the exported API.

The intent is to allow TypeScript code to import libraries written with Closure-style type declarations. Having the clutz generated declarations allows type-checking in the TypeScript compiler and IDE tooling (for highlighting errors and type-sensitive auto-complete) as if the imported code was written in TypeScript.

Supported versions

We lack the resources to make Clutz releases or support multiple versions of dependent tools simultaneously. You'll have the most success with Clutz if you use it with:

Closure Compiler at HEAD: whatever maven thinks -SNAPSHOT is.
A recent version of TypeScript: the test suite runs against the version of typescript in npm-shrinkwrap.json, so that is always a good choice.

Example usage

We don't offer a binary distribution, so first you need to build from source. From the root directory run:

$ npm install
$ ./gradlew build installDist # or just "gradlew" on Windows
...
BUILD SUCCESSFUL

You can use Clutz from the command line using the wrapper script produced by Grade or by executing the JAR file in build/libs/ yourself. Here is a sample execution:

$ PATH=$PATH:./build/install/clutz/bin
$ clutz path/to/my/source1.js path/to/my/source2.js ...
        --externs path/to/closure-compiler/externs/es3.js path/to/closure-compiler/externs/es5.js ...
        -o out.d.ts

This creates TypeScript type definitions in out.d.ts for all the closure types discovered in the inputs. Symbols which were declared with goog.provide('x') may be imported in TypeScript as import x from 'goog:x';. For full explanation of what TypeScript types are produced for different Closure usages, see the .js and .d.ts files in src/test/com/google/javascript/clutz.

When compiling TypeScript code that depends on the closure code, include the src/resources/closure.lib.d.ts file along with out.d.ts.

Note that clutz requires that your code can be compiled with Closure Compiler. If you get errors, try reproducing them without clutz, by compiling your code with Closure alone. The arguments for invoking clutz are intentionally similar to the arguments for invoking the Closure compiler. You can find the additional compiler flags that clutz passes to Closure Compiler in src/main/java/com/google/javascript/clutz/Options.java. If the failure is reproducible this way, then you have a closure type error in your code (or a bug in Closure Compiler).

Gents - Closure to TypeScript converter

This repository also hosts gents - tool that generates TypeScript code out of Closure annotated .js. We host it in this repo together with clutz because they both wrap Closure Compiler to get the type information. As such gents shares clutz restriction that it only accepts code that is valid well-typed Closure JavaScript.

Details about some specific conversions follow:

Module Conversion

gents converts Closure goog.module and goog.provide module/namespaces into TypeScript modules. On the exporting side, it converts export assignments into TypeScript export statements. On the importing side, it converts goog.require statements into TypeScript imports. Due to naming issues, this may result in the renaming of the imported symbols.

// file a.js
goog.module('mod.A');
exports = function(n) { return n; };

// file b.js
goog.provide('provided.B');
provided.B.val = 4;

// file c.js
goog.module('importer.C');
var A = goog.require('mod.A');
var B = goog.require('provided.B');

/** @type {number} */
var num = A(B.val);

Is converted to:

// file a.ts
export const A = function(n) { return n; };

// file b.ts
export const val = 4;

// file c.ts
export {};
import {A} from "./a";
import * as B from "./b";

let num: number = A(B.val);

Class Conversion

gents converts @constructor annotated functions and goog.defineClass into ES6 class declarations. Additionally, it moves all prototype and static method/field declarations into the class.

/**
 * @param {number} n
 * @constructor
 */
function A(n) {
  /** @type {number} */
  this.num = n;
}

/** @return {number} */
A.prototype.foo = function() { return 4; };
/** @return {boolean} */
A.bar = function() { return false; };
/** @type {boolean} */
A.x = true;

Is converted to:

class A {
  num: number;
  static x: boolean = true;

  constructor(n: number) {
    this.num = n;
  }
  foo(): number {
    return 4;
  }
  static bar(): boolean {
    return false;
  }
}

Type Conversion

gents converts JSDoc annotated JavaScript into the proper TypeScript declaration. Note that just like with classes, gents only converts explicitly annotated types. This is to make sure gents doesn't accidentally aggressively infer the types of every variable and generate giant type declarations.

Known Issues and TODOs

Github issues

rrdelaney/clutz

Clutz - Closure to TypeScript Declarations (.d.ts) generator.