streaming / iterative fs.readdir

[jonathanong]

since we're in ES6 territory now, i'm thinking the sync version should be an iterable

var dirs = fs.readdirIter(__dirname);
for (dir of dirs) {

}

and have the async version be an object stream:

var stream = fs.readdirStream(__dirname);
stream.on('data', dir => )

See: nodejs/node-v0.x-archive#388

[novacrazy]

Using generators/iterators in io.js where they make sense would be a good addition.

[cjb]

Does this depend on the work in joyent/libuv#1574 to be merged first? I don't think it's in libuv yet.

[vkurchatkin]

👍

in the future asynchronous version could return an observable:

for (dir on fs.readdir(__dirname)) {

}

[hemanth]

👍

[Qard]

I'm all for the new named versions. We don't want to break compatibility with existing code by changing behaviour of existing functions, but new stuff could work. I'm not sure what the policy is yet on new interfaces that deviate from node.js though.

@iojs/tc Thoughts?

[rvagg]

Where else does an interface like this make sense? Would this be a one-off of would there be a flood of requests to add the same style interface to other core APIs?

[jonathanong]

@rvagg I looked for any other APIs that would look like this but I couldn't find any. I think this may be a one-off.

[rvagg]

I think the way forward on this is for someone here to propose a change in a PR and then we'll escalate that to a TC discussion because it would be good to cover the question of whether adopting a new style of API is desirable. If it's too much work to come up with an initial implementation then we could just elevate this issue, it'd just be more of a hypothetical discussion then.

[Qard]

I think the streams version makes sense. I would test the iterator design in userland though. It can apply to any sort of stream, really. And it's easy enough to abstract a stream as an iterator in userland.

[Fishrock123]

The eventual observables thing sounds pretty rad.

[jonathanong]

@Qard how would you create an iterator from a stream? streams are async... iterators are not...

@cjb i don't think it's merged. i'm going to open an issue in libuv now

[Qard]

Just use co? (or something similar)

[domenic]

OK, a few things:

• Iterables make no sense here; they are synchronous. (Generators are just iterables with .throw() and .return() methods; they don't make any sense either.)
• There are vague designs by one TC39 committee member for adding RxJS-style observables to the language, along with for-on syntax. I doubt that will make the ES2016 train since no implementers have yet expressed interest, but I could be wrong. Regardless, it's very tentative. (There's another competing proposal, async iterables, that might be a better fit for this use case in particular.)
• In the meantime, Node.js has an awkward version of observables/async-iterables/etc. already: object-mode streams. That's clearly the right choice for this situation, even if in the long run there becomes a language-level primitive for plural asynchronous values (similar to promises being the primitive for singular asynchronous values, or iterables being the primitive for plural synchronous values).

So I don't think this should be a new style of API. Just an object mode stream is fine.