Make it easier to define implementations of NetworkBehaviour

[thomaseizinger]

See patches for details.

Not sure how controversial this proposal is :)

[mxinden]

Looks good to me other than inject_event. What do you think of my comment below @thomaseizinger?

[mxinden]

A NetworkBehaviour that does not receive any events from its ProtocolsHandler should use void::Void on their ProtocolsHandler::OutEvent, thus checked at compile time, no?

I would prefer the above over a default implementation. What do you think? If you agree, could you add a doc comment to inject_event?

[thomaseizinger]

We can do that yeah.

I approached this more from a prototyping perspective: If I want to define a new NetworkBehaviour, what is the least amount of stuff I am faced with?

I was also tempted to default poll actually. An AddressBook style NetworkBehaviour doesn't need poll for example :)

I am not sure inject_event with match event { } is actually cleaner. The only thing it protects you from is forgetting to deal with your events if you change the ProtocolsHandler.

For this to work, it implies that people actually override it with match event { } in the first place and not just leave it blank. At least rust-analyzer autocompletes trait-impls with todo!() though and the path of least resistance is to either leave those in or delete them 🤷‍♂️

In any case, defaulting the others is already an improvement so I'll do that.

[mxinden]

@thomaseizinger can you fix the failing tests below? Other than that, this looks good to me.

error[E0046]: not all trait items implemented, missing: `inject_event`
   --> swarm/src/test.rs:68:1

   ::: swarm/src/behaviour.rs:130:5

[thomaseizinger]

@thomaseizinger can you fix the failing tests below? Other than that, this looks good to me.

error[E0046]: not all trait items implemented, missing: `inject_event`
   --> swarm/src/test.rs:68:1

   ::: swarm/src/behaviour.rs:130:5

Ah damn. Still need to get used to my new RA based setup ...

[mxinden]

Can you take another look at the current failure @thomaseizinger?

error[E0223]: ambiguous associated type
  --> swarm/src/test.rs:89:12
   |
89 |         _: ProtocolsHandler::OutEvent
   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<Type as protocols_handler::ProtocolsHandler>::OutEvent`

error: aborting due to previous error

[thomaseizinger]

Can you take another look at the current failure @thomaseizinger?

error[E0223]: ambiguous associated type
  --> swarm/src/test.rs:89:12
   |
89 |         _: ProtocolsHandler::OutEvent
   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<Type as protocols_handler::ProtocolsHandler>::OutEvent`

error: aborting due to previous error

Argh, I ran clippy without --all-targets.

[thomaseizinger]

Hopefully everything is done now @mxinden !

Sorry about the mess, transitioning local setup at the moment and not quite used to it yet ...

[mxinden]

Thanks @thomaseizinger!