delay.reject()

[sindresorhus]

Idea from: https://github.com/ariporad/ava/blob/c7b0154f8ae181e892d58ab1d50aee6154a9a743/test/test.js#L7-L12

delay.reject(100, 'message');
delay.reject(100, new Error('message')); // equivalent to the above

If a string, it's converted to an Error, otherwise passed through.

I know the first case is not like Promise.reject(), but is there any good reason not to reject with an error?

@ariporad @jamestalmage Do you think it would be useful to have this here?

[ariporad]

Absolutely. I think this wouldn't be hard to add, and would be rather useful. However, I think that if we were to add this we should also do delay.resolve, and not do the error conversion thing (that makes sense in the context of those AVA tests, but not really in general).

I'm happy to submit a PR if you want.

[sindresorhus]

However, I think that if we were to add this we should also do delay.resolve

Why? Do you need it for something? I kinda like how I can just write delay(), which is the 95% use-case. .reject() is just an added bonus.

[ariporad]

Completeness. It would be strange to have one and not the other. Plus, it's really trivial to write.

[sindresorhus]

But now you have two ways of doing the same thing, which I'm not a big fan of. I usually have one default export for the main use-case and then if there's any nice-to-haves, they're put as methods.

Example: https://github.com/sindresorhus/log-update#logupdatetext-

[sindresorhus]

and not do the error conversion thing (that makes sense in the context of those AVA tests, but not really in general).

Why do think we shouldn't do it? Most will use new Error(), so I thought it would be nice to make the main use-case simpler. And also prevent anyone from shooting themselves in the foot and rejecting a string or something non-error. I think Promise.reject() only supports this for consistency with throw. I don't see why we can't improve the IMHO broken default behavior.

[ariporad]

In regard to the two-ways to do something: Sometimes its worth a little redundancy to avoid confusion down the road.

Imagine that six months ago you wrote the following code:

var delay = require('delay');

// ...

return delay.reject(1000, new Error('foo'));

Without looking at the docs, you'd assume that you can use delay.reject. Now imagine that you're in the same file, and you see this:

// FIXME: every once in a while, this resolves before the promise from #doSomethingElse, and causes problems.
return Promise.reject('foo');

You'd assume that you could just do this:

// FIXME: every once in a while, this resolves before the promise from #doSomethingElse, and causes problems.
return delay.reject(10, 'foo');

[sindresorhus]

Ok, how about we add it undocumented then?

[jamestalmage]

I am 👍 for the idea. Not sure where i stand on the string to error conversion. Seems a little magic. Also, this is primarily for testing - and if I am accepting user generated promises in my API, correctly handling non-error rejections is a something I want to test.

[ariporad]

Here's three reasons why I wouldn't do that:

1. Then they'll have to go digging in the source code to figure out why
   their string is being cast to an error.
2. If it's not documented, it doesn't exist. Semver doesn't apply. Don't
   use it.
3. No.

[jamestalmage]

👎 for resolve. Keep it simple.

[sindresorhus]

Ok. No .resolve() (sorry @ariporad, but I'm an extreme minimalist) and no magic string to error conversion. PR welcome :)

[jamestalmage]

What should we do if used like this:

someprise.then(delay.reject(100));

someprise.then(delay.reject(100, new Error()));

[sindresorhus]

@jamestalmage Same as Promise.reject() I assume? Or do you have a better suggestion?

[jamestalmage]

With delay we just delay and then pass through the result. I think delay.reject(100) with only one arg should delay and reject with whatever it was called with.

You can then do:

somePromise.then(delay(100), delay.reject(100))

To delay resolution and rejection

[ariporad]

Never mind. That makes sense.

[ariporad]

When I'm home in an hour or so I'll submit a PR

[sindresorhus]

👍 Good idea.