core/muxing: Replace `Into<io::Error>` bound on `StreamMuxer` with `std::error::Error` #2710

thomaseizinger · 2022-06-16T09:23:26Z

Description

This allows us to preserve the type information of a muxer's concrete
error as long as possible. For StreamMuxerBox, we leverage io::Error's
capability of wrapping any error that implements Into<Box<dyn Error>>.

Links to any relevant issues

~~This is a stacked PR on top of #2707 and thus a draft but is otherwise ready to review.~~

Open Questions

Change checklist

I have performed a self-review of my own code
I have made corresponding changes to the documentation
~~I have added tests that prove my fix is effective or that my feature works~~
A changelog entry has been made in the appropriate crates

elenaf9 · 2022-06-20T14:38:01Z

core/src/muxing/boxed.rs

@@ -38,6 +39,7 @@ impl<T> StreamMuxer for Wrap<T>
 where
    T: StreamMuxer,
    T::Substream: AsyncRead + AsyncWrite + Send + Unpin + 'static,
+    T::Error: Into<Box<dyn Error + Send + Sync>>,


Suggested change

T::Error: Into<Box<dyn Error + Send + Sync>>,

T::Error: Error + Send + Sync>,

Nit: Wouldn't this simpler trait bound also work, given that Into<Box<dyn ..>> is auto-implemented for E: Error + Send + Sync?

Probably yes. I've copied the bounds from std::io::Error::new because that is where I am passing the type to. Omitting the Into here is probably okay :)

I decided to put the Error bound directly on the associated type so I don't have to repeat it everywhere. The Send + Sync bounds stay on higher layers for consistency with other bounds.

I decided to put the Error bound directly on the associated type so I don't have to repeat it everywhere.

It is only in 4 locations, right? a479eb8 I would prefer bounds to be as close to where they are used as possible. If I am not mistaken StreamMuxer doesn't need type Error to implement Error, right? I liked how previously this pull request would remove the bound on StreamMuxer.

It doesn't. It also doesn't necessarily need Substream to implement AsyncRead + AsyncWrite but it is a bit pointless if it doesn't.

If we remove the Error bounds, we should also remove AsyncRead + AsyncWrite for consistency but that will get a bit redundant I think.

The current style seems to be that functional bounds are put on associated types and auto-traits are left off.

elenaf9 · 2022-06-20T14:42:24Z

swarm/src/connection/substream.rs

@@ -134,7 +134,7 @@ where
    pub fn poll(
        &mut self,
        cx: &mut Context<'_>,
-    ) -> Poll<Result<SubstreamEvent<TMuxer, TUserData>, IoError>> {
+    ) -> Poll<Result<SubstreamEvent<TMuxer, TUserData>, TMuxer::Error>> {


Not in scope for this PR, but while reviewing I was wondering: Do we even need the TMuxer generic on Muxing? I think the actual type is always StreamMuxerBox. Muxing is private the swarm crate and only used by Connection and there we already use the concrete StreamMuxerBox.

I am going to inline the entire Muxing type into Connection once poll_outbound is removed from StreamMuxer. This is already done in #2648 if you want to see what it looks like :)

I am also tempted to inline HandlerWrapper and centralize all the connection handling logic directly in Connection. This would remove quite a bit of indirection because substreams would directly be passed from the StreamMuxer to the ConnectionHandler.

thomaseizinger · 2022-06-20T15:27:48Z

Rebase only to stay up to date with #2707.

This allows us to preserve the type information of a muxer's concrete error as long as possible. For `StreamMuxerBox`, we leverage `io::Error`'s capability of wrapping any error that implements `Into<Box<dyn Error>>`.

thomaseizinger · 2022-06-23T11:56:02Z

Rebase only includes diff of master since this has been opened: https://github.com/libp2p/rust-libp2p/compare/c2106db78e6af1fc78f33c1f780498c4c5f59a70..a28a7c51eded33886ccd279e64c423afafb5e907

thomaseizinger changed the base branch from master to refactor/introduce-substream-box June 16, 2022 09:23

thomaseizinger mentioned this pull request Jun 16, 2022

core/muxing: Fix StreamMuxer::Error to io::Error #2664

Closed

4 tasks

thomaseizinger marked this pull request as ready for review June 16, 2022 09:29

thomaseizinger requested review from mxinden and elenaf9 June 16, 2022 09:29

thomaseizinger marked this pull request as draft June 16, 2022 09:29

thomaseizinger mentioned this pull request Jun 18, 2022

src/error: Add From<ConnectionError> for io::Error implementation libp2p/rust-yamux#136

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elenaf9 approved these changes Jun 20, 2022

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thomaseizinger changed the title ~~core/muxing: Remove Into<io::Error> bound from StreamMuxer::Error~~ core/muxing: Replace Into<io::Error> bound from StreamMuxer::Error with std::Error Jun 20, 2022

thomaseizinger changed the title ~~core/muxing: Replace Into<io::Error> bound from StreamMuxer::Error with std::Error~~ core/muxing: Replace Into<io::Error> bound on StreamMuxer with std::error::Error Jun 20, 2022

thomaseizinger force-pushed the refactor/introduce-substream-box branch from cdfa81e to f014c29 Compare June 20, 2022 15:22

thomaseizinger force-pushed the refactor/remove-io-error-bound branch from 37a23c4 to 27638ac Compare June 20, 2022 15:27

This was referenced Jun 22, 2022

core/muxing: Redesign StreamMuxer trait #2648

Closed

Re-design the StreamMuxer trait #2722

Closed

Base automatically changed from refactor/introduce-substream-box to master June 23, 2022 11:52

thomaseizinger added 9 commits June 23, 2022 13:53

core/muxing: Remove Into<io::Error> bound from StreamMuxer::Error

ed371e1

This allows us to preserve the type information of a muxer's concrete error as long as possible. For `StreamMuxerBox`, we leverage `io::Error`'s capability of wrapping any error that implements `Into<Box<dyn Error>>`.

Use ? in Connection::poll

8e222b1

Use ? in muxing::boxed::Wrap

88ce2f0

Use futures::ready! in muxing::boxed::Wrap

6cce828

Fill PR number into changelog

0dea55f

Put Error + Send + Sync bounds directly on StreamMuxer::Error

e017cae

Move Send + Sync bounds to higher layers

b5da12f

Use map_inbound_stream helper

80a35b8

Update changelog to match new implementation

a28a7c5

thomaseizinger force-pushed the refactor/remove-io-error-bound branch from c2106db to a28a7c5 Compare June 23, 2022 11:53

thomaseizinger marked this pull request as ready for review June 23, 2022 11:56

thomaseizinger mentioned this pull request Jun 23, 2022

core/muxing: Flatten StreamMuxer interface to poll_{inbound,outbound,address_change,close} #2724

Merged

4 tasks

mxinden approved these changes Jun 24, 2022

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thomaseizinger merged commit 0f40e51 into master Jun 24, 2022

thomaseizinger deleted the refactor/remove-io-error-bound branch June 24, 2022 06:26

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core/muxing: Replace `Into<io::Error>` bound on `StreamMuxer` with `std::error::Error` #2710

core/muxing: Replace `Into<io::Error>` bound on `StreamMuxer` with `std::error::Error` #2710

thomaseizinger commented Jun 16, 2022 •

edited

elenaf9 Jun 20, 2022

thomaseizinger Jun 20, 2022

thomaseizinger Jun 20, 2022

mxinden Jun 21, 2022 •

edited

thomaseizinger Jun 21, 2022 •

edited

elenaf9 Jun 20, 2022

thomaseizinger Jun 20, 2022

thomaseizinger commented Jun 20, 2022

thomaseizinger commented Jun 23, 2022

	T::Error: Into<Box<dyn Error + Send + Sync>>,
	T::Error: Error + Send + Sync>,

core/muxing: Replace Into<io::Error> bound on StreamMuxer with std::error::Error #2710

core/muxing: Replace Into<io::Error> bound on StreamMuxer with std::error::Error #2710

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thomaseizinger commented Jun 16, 2022 • edited

Description

Links to any relevant issues

Open Questions

Change checklist

elenaf9 Jun 20, 2022

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thomaseizinger Jun 20, 2022

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mxinden Jun 21, 2022 • edited

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thomaseizinger Jun 21, 2022 • edited

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thomaseizinger commented Jun 20, 2022

thomaseizinger commented Jun 23, 2022

core/muxing: Replace `Into<io::Error>` bound on `StreamMuxer` with `std::error::Error` #2710

core/muxing: Replace `Into<io::Error>` bound on `StreamMuxer` with `std::error::Error` #2710

thomaseizinger commented Jun 16, 2022 •

edited

mxinden Jun 21, 2022 •

edited

thomaseizinger Jun 21, 2022 •

edited