Modularize polyfills

[nippur72]

As far as I know, polyfill functions are repeated in each file they are needed, resulting in lot of duplicate code.

I suggest to optionally emit them as a module, so that they appear once in a bundled project.

E.g. instead of:

var __extends = (this && this.__extends) || function (d, b) {
    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};

var myclass= (function (_super) {
    __extends(myclass, _super);
    // ...

emit this:

var __extends = require("typescript-polyfills").extends;

var myclass= (function (_super) {
    __extends(myclass, _super);
    // ...

[kitsonk]

var __extends = require("typescript-polyfills").extends;

This assumes everyone is using the Common JS module loader. What about those using an AMD loader, a SystemJS loader, etc?

[nippur72]

oh that was just an example, I guess we could actually use the existing TypeScript capability of turning any import code into the chosen module loader. E.g. a sort of intermediate compilation with:

import { extends as __extends } from "typescript-polyfills";

var myclass= (function (_super) {
    __extends(myclass, _super);
    // ...

The basic idea here is to put polyfills into modules to save space. But perhaps that work might be delegated to the bundlers (webpack/browserify/etc...) by the use of a specific plugin.

[kitsonk]

Still doesn't deal with how the module will be resolvable...

Anyways a quick search shows that this is a dupe of #1350 which was discussed and the solution was #2901 (noEmitHelpers) flag.

[nippur72]

thanks and sorry for the dupe--I always check but sometimes you don't know what terms to look for.

[kitsonk]

Also, for completeness, #3364 is delivering the helpers as a module for TS2.0 as per the roadmap.