Add enumerate combinator to Stream

[zaharidichev]

Motivation

Motivation is to provide an enumarete combinator, much like in Iterator. The issue for that can be found here: #741

Solution

Simply provided Stream::enumerate on StreamExt

Since this is my first PR any kind of feedback will be greatly appreaciated :)

[NeoLegends]

Sorry for my comment here since I'm not a maintainer of any kind, but I think this belongs into the futures-rs repository, since it doesn't need anything of the tokio runtime to work, does it? :)

see https://github.com/rust-lang-nursery/futures-rs

[zaharidichev]

@NeoLegends the issue is in this repository, so I thought that it can go here. Also, there is StreamExt that I thought has the purpose of adding such additional functionality on top of the Stream coming from futures-rs. Correct me if I am wrong...

[davidbarsky]

@zaharidichev Given that futures-rs is primarily targeted at Futures 0.3/std and Tokio isn't, I think Tokio is a good place to open a PR, but @carllerche can correct me.

[davidbarsky]

These changes look good to me, but I wonder if it makes sense to have a corresponding Sink implementation in the same way that Fuse.

[zaharidichev]

@davidbarsky The reason I did not put a forwarding sink impl is because I saw that throttle does not have one. Not sure whether this is a valid reason but in any case it would be helpful if somebody explains why throttle does not have a Sink and whether enumarete should have one :)

[davidbarsky]

Accident of history, as far as I can tell, but others can more clearly explain. Enumerate is closer to the “iterator-like” combinators than throttle. Since the iterator-like combinators tend to have Sink implementations (skip_while, chunks). I think that because of the more iterator-like features of enumerate, it should also have a corresponding Sink interface.

[zaharidichev]

thanks for the explanation @davidbarsky. I have added a sink impl

[davidbarsky]

Thanks @zaharidichev! I think this looks good. I can merge if build succeeds, @carllerche?

[zaharidichev]

Thanks @davidbarsky Since I am a bit new to this repo, is there some other biginner friendly ticket I can pick up ?

[davidbarsky]

@zaharidichev Anything under the label “Help Wanted”. In my opinion, the biggest return on effort (and the best way to go from “beginner” to “expert” extremely quickly) is documentation. Issues are tracked at tokio-rs/doc-push, and picking one of those issues up and opening a PR on https://github.com/tokio-rs/website would be extremely helpful.

[zaharidichev]

Yes, documentation sounds like a good way to self educate. I will pick something up from there :) Thanks !

[zaharidichev]

I wonder why the build is showing as in progress when it actually failed on stable ?

[LucioFranco]

@zaharidichev seems like the travis forgot to update the commit but it seems that try_ready! isn't in scope. https://travis-ci.org/tokio-rs/tokio/jobs/476408795#L672

[zaharidichev]

Yes @LucioFranco, sorry about that. It passes now.

[LucioFranco]

Overall this LGTM 👍

[carllerche]

LGTM 👍 Just some minor requests inline.

[carllerche]

I think this needs to be a pub export.

[carllerche]

Can we avoid making this public? Construction can happen via the stream trait.

[zaharidichev]

Sorry, not entirely sure how that works. Can you give me a clue. Essentially we need to make it module private but how does that tie in with the pub export that you mentioned earlier ?

[carllerche]

pub(crate) fn new(...) then call Enumerate::new in `StreamExt::enumerate().

[zaharidichev]

@carllerche I think I have addressed your comments. Is this good to merge now ?

[carllerche]

@zaharidichev Just one missing pub here then it should be good. (the use in futures.rs should be pub so that Enumerate can be named via tokio::util::futures::Enumerate.

[zaharidichev]

@carllerche Can that be merged now ?

[carllerche]

👍