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aurelia / tools-ts

The shared set of tools that are used for TypeScript library builds.
MIT License
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tslib discussion #3

Open jods4 opened 6 years ago

jods4 commented 6 years ago

Per @StrahilKazlachev request:

We need to settle how we want to handle TS helpers in codegen.

When compiling to ES5 -- or even ES6 (e.g. decorators) -- TS makes use of a few helper functions, for example __extends when using class inheritance in ES5, __rest when using rest properties, __decorate when using decorators.

By default, used helpers are emitted at the top of each output file (only helpers used in that file, of course). Aurelia is made of many files and it really adds up to a lot of redundant code. Even more so if we use __awaiter or __generator, which are large.

Fortunately, Typescript has two options to address this problem:

--noEmitHelpers does what it says. The generated code won't run unless your provide helpers in some way (likely a set of global variables).

--importHelpers imports the required helpers from tslib at the top of generated file. Module tslib is distributed and maintained by MS.

I think the importHelpers solution is the simplest, is maintained by MS (when there's a new helper or one needs changing), optimizes with bundlers like Webpack or Rollup and works along other TS code compiled with importHelpers (e.g. app code or other libs).

The main drawback that @EisenbergEffect doesn't like is that this means Aurelia would have an external dependency on tslib, whereas today it has none.

I would point out that all serious projects today use a bundler and that if someone doesn't want to use tslib, it's easy to map the name to another arbitrary module, even one distributed with Aurelia if we really want to go this route.

EisenbergEffect commented 6 years ago

I think I'm ok with the dependency on tslib. How large is it?

jods4 commented 6 years ago

@EisenbergEffect The whole thing is 200 lines, 10K, before minification and gzip. Quite small: https://github.com/Microsoft/tslib/blob/master/tslib.js

There's even a smaller one when targetting es6.

aluanhaddad commented 6 years ago

I use tslib in my aurelia projects, it really cuts down on code size and makes the transpiled code much more readable since you don't have to scroll through the 50 lines of helpers otherwise emitted for say an async *.

It works out of the box with both the 0.19.x and 0.20.x forks of SystemJS as of 1.8.0.