Support `register` to allow users to just require `.ts` files

[basarat]

Proposal

You simply do require('typescript').register() and then all require calls e.g. var foo = require('./foo') would load foo.ts if foo.js/json/etc are not found.

This would mean we would compile in-memory and completely skip all type checking and do a fast emit. This would however greatly help increase .ts adaption IMHO.

Currently there is a userland maintained : https://github.com/TypeStrong/ts-node

Motivation

CoffeeScript supports this via require('coffee-script').register(); (synonym for require('coffee-script/register');) so that once you call this function it patches require to support .coffee files.

E.g.

• Atom does this for coffee : here and here
• Grunt does this here

The implementation for coffeescript can be found here : http://coffeescript.org/documentation/docs/register.html

Where in typescript

This can potentially be done in an external NPM package, but:

• having it officially support would enhance adaption.
• give better statistics for typescript npm package as users would start requireing typescript (coffeescript downloads https://www.npmjs.com/package/coffee-script)

[billti]

I left a comment in the pull request also to this effect, but this functionality is deprecated in the Node API. Specifically, it states at https://nodejs.org/api/globals.html#globals_require_extensions

*Deprecated* In the past, this list has been used to load non-JavaScript modules into Node by compiling them on-demand. However, in practice, there are much better ways to do this, such as loading modules via some other Node program, or compiling them to JavaScript ahead of time.

While it does go on to say, Since the Module system is locked, this feature will probably never go away, it still seems undesirable to add new features the depend on deprecated features.

[mkusher]

@billti I can replace this register hook with bin ts-node(like babel-node), which will hook require and start application. And there'll be no way to "pollute" npm using this bin, what do you think?

[mhegazy]

We have been getting consistent feedback about this. i think we should reconsider the current position.

[basarat]

We have been getting consistent feedback about this. i think we should reconsider the current position.

FWIW @blakeembrey has done an excellent job : https://github.com/TypeStrong/ts-node 🌹

[blakeembrey]

Also just a note, but I don't recommend making it too easy to do this. It's good in specific contexts which should be heavily documented (yeah, guilty, missing in ts-node - I made assumptions on the context people would try to use it), but you don't want to get into the situation like CoffeeScript where every CoffeeScript module was published as is on NPM and everyone used the register functionality which really brought down the quality in the node ecosystem (E.g. non-JS published on NPM won't work out of the box with package bundlers).

[igl]

Having it in a stand-alone module ala require('typescript/register') wouldn't clutter up lib/typescript.js with node specific code that is not used/would break in other envs.
Same reason why coffee and babel have it in seperate modules.

I like the idea of having a fast compile-without-type-checks for hot module reloading.
Type-checking can be done in a slow threaded rebuild on the side.

[amcdnl]

@blakeembrey how many people are going to use a TS project that don't use TS though? I think you should start tspm ;)

[blakeembrey]

@amcdnl I think I missed some context, but you're joking about creating a TypeScript package manager so we can skip the JavaScript publishing? I think your first question is my point, most peoples main audience is still non-TS users. Anyway, not a fun idea - that'll take a long time to build, even though I got a bit of experience building typings now 😉

[amcdnl]

@blakeembrey Yes, I was joking! I think it doesn't really matter whether ur a TS user or not, u want to take advantage of the rich JS community.

Side note: I was able to get this working w/ ts-node but breakpoints are never hit in my IDE ( VSCode ).

@basarat If this would "...greatly help increase .ts adaption IMHO", why is it not landing til 2.0? That seems pretty far out ATM.

[felixfbecker]

The only reason I want this is so I can do gulp --require "typescript/register" and name my gulpfile gulpfile.ts