Add test for type definition validation?

[kwonoj]

There are some cases of type definition does not work as expected like reported issue #660, #642, #635, Came to feel it'd be helpful if there's compile-time type signature validation test is included CI.

It'll not be kind of unit test, simply write down basic signatures of operator invocation in typescript instead of plain javascript, let CI try to compile it only (does not execute). Compilation result will tell if current type signature works in expected way or not. Course it can't cover whole aspect of signature, but at least can have minimum lines of basic usages.

[benlesh]

It sounds cool... @robwormald @jeffbcross what do you think about this? Do you guys do anything similar for Angular?

[robwormald]

Yeah, I think this is a great idea. It's a little tricky to test, but the original issue that I posted cropped up by doing something similar:

class Response {
  constructor(private _text:string){}
  toJson():Object { return JSON.stringify(this._text); }
}

let o = new Observable(obs => {
  obs.next(new Response('{"foo":"bar"}'));
  obs.complete();
});

obs.map(res => res.toJson()).subscribe() //complains - {} does not have a .toJson() method!

should be just a matter of setting up TS to compile some basic usage code with some typed classes. Would be happy to contribute here if you can get the mechanics set up @kwonoj

[robwormald]

In angular2, our tests are written in TS and so such issues get caught when the tests are being compiled.

[kwonoj]

As @robwormald mentioned, main difference between ng2 is RxJS test cases are written in JS.

I'll try to spend some times to think about ergonomics setup for this and create PR for proposal.

[kwonoj]

This could be achieved moving current test cases into typescript based one as same as Angular2 does, if circumstances allows.

[kwonoj]

I'm assigning this myself for evaluating if current test cases can be moved into typescript based one.

[kwonoj]

Currently there are 3 (including this) way proposed,

• convert unit test to typescript based, add additional test cases in existing tests (Proposal : migrate unit test to typescript  #826)
• separate test running for type validation only with custom runner using compiler api (Proposal for type validation test runner #667)
• separate test, running with compiler out of box (test(typings): Added tests for typings. #1189) by @david-driscoll