feat: enable tslib helpers

Type of Issue

[ ] Bug Report
[x] Feature Request

Description

Not sure if you already have considered this, however, doesn’t make sense to enable tslib helpers by default? if not some kind of config override might be needed in order to allow this.

all it needs

    "compilerOptions": {
        "importHelpers": true
    }

1. add tslib as dependency

https://github.com/Microsoft/tslib

Expected Behaviour

tslib helpers not emitted in the output, as this will make the build smaller.

Version Information

ng-packagr: v2.0.0-rc.4

[stephenlautier]

Sure I will check it out 👍

Not sure if it make sense to add tslib as a dependency in the generated package.json, or you recommend simply have to it to add it to your main package.json manually?

[dherges]

Hi @stephenlautier,

considered, yes. Aren’t the __ decorate, __extends, and so on helpers not required to be included at least once in the esm5 bundle?

You made me check Angular’s GitHub builds repos and @angular/common is:

FESM’5 Bundle:

import { __assign, __extends } from 'tslib';

https://github.com/angular/common-builds/blob/master/esm5/common.js

UMD Bundle:

var extendStatics = Object.setPrototypeOf ||
    ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
    function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };

function __extends(d, b) {
    extendStatics(d, b);
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
}

var __assign = Object.assign || function __assign(t) {
    for (var s, i = 1, n = arguments.length; i < n; i++) {
        s = arguments[i];
        for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p)) t[p] = s[p];
    }
    return t;
};

https://github.com/angular/common-builds/blob/master/bundles/common.umd.js#L32-L44

---

TL;DR: you’re right … the quickest way to get there is to set "importHelpers": true and then let rollup inline the tslib helpers to the top of the bundles.