feat(core): make the upgrade module an implementation detail

[thomaseizinger]

Description

Resolves: #3748.

Notes & open questions

Draft because stacked.

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

[thomaseizinger]

In a later step, we can simplify some of this code down to use boxed futures which should save us quite a bit of code!

[mxinden]

Can you remove the usage in libp2p-plaintext @thomaseizinger?

See CI failure:

---- src/lib.rs - PlainText1Config (line 58) stdout ----
error[E0603]: function `apply` is private
error: doctest failed, to rerun pass `-p libp2p-plaintext --doc`
Error:   --> src/lib.rs:64:27
   |
9  |     libp2p_core::upgrade::apply(
   |                           ^^^^^ private function
   |
note: the function `apply` is defined here
  --> /home/runner/work/rust-libp2p/rust-libp2p/core/src/upgrade.rs:70:5
   |
70 |     apply, apply_inbound, apply_outbound, InboundUpgradeApply, OutboundUpgradeApply,
   |     ^^^^^

error: aborting due to previous error

[thomaseizinger]

Can you remove the usage in libp2p-plaintext @thomaseizinger?

I thought I had removed all usages before! Fixed now :)

[mxinden]

@thomaseizinger libp2p-plaintext tests still failing:

---- src/lib.rs - PlainText1Config (line 58) stdout ----
error[E0271]: type mismatch resolving `<PlainText1Config as InboundUpgrade<Negotiated<RwStreamSink<Chan>>>>::Output == (PeerId, _)`
Error:    --> src/lib.rs:64:17
    |
9   |   .authenticate(PlainText1Config {})
    |    ------------ ^^^^^^^^^^^^^^^^^^^ expected `(PeerId, _)`, found `Negotiated<RwStreamSink<Chan>>`
    |    |
    |    required by a bound introduced by this call
    |
    = note: expected tuple `(libp2p_identity::peer_id::PeerId, _)`
              found struct `multistream_select::negotiated::Negotiated<rw_stream_sink::RwStreamSink<Chan>>`
note: required by a bound in `libp2p_core::transport::upgrade::Builder::<T>::authenticate`
   --> /home/runner/work/rust-libp2p/rust-libp2p/core/src/transport/upgrade.rs:104:42
    |
104 |         U: InboundUpgrade<Negotiated<C>, Output = (PeerId, D), Error = E>,
    |                                          ^^^^^^^^^^^^^^^^^^^^ required by this bound in `Builder::<T>::authenticate`

error[E0271]: type mismatch resolving `<PlainText1Config as OutboundUpgrade<Negotiated<RwStreamSink<Chan>>>>::Output == (PeerId, _)`

[thomaseizinger]

Yeah I noticed. Should we just bin Plaintext1Config? It is not compatible with the upgrade API so why would anyone use that at all?

[mxinden]

Removing Plaintext1Config sounds good to me. I don't see a use-case where Plaintext2Config is not enough.

[thomaseizinger]

Removing Plaintext1Config sounds good to me. I don't see a use-case where Plaintext2Config is not enough.

Opened a PR here: #3940