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feat(core): specify event listener API #14735

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merged 6 commits into from
Jan 24, 2023
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@aaronc aaronc commented Jan 23, 2023

Description

Ref #14683

This adds an API for modules to register event listeners in core.


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@aaronc aaronc marked this pull request as ready for review January 23, 2023 16:41
@aaronc aaronc requested a review from a team as a code owner January 23, 2023 16:41
@github-prbot github-prbot requested review from a team, kocubinski and tac0turtle and removed request for a team January 23, 2023 16:41
Comment on lines +11 to +16
type HasEventListeners interface {
AppModule

// RegisterEventListeners registers the module's events listeners.
RegisterEventListeners(registrar *EventListenerRegistrar)
}
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I have a question on why to expose EventListenerRegistrar in core, shouldn't that be runtime?

The core interface could simply be:

Suggested change
type HasEventListeners interface {
AppModule
// RegisterEventListeners registers the module's events listeners.
RegisterEventListeners(registrar *EventListenerRegistrar)
}
type HasEventListeners interface {
AppModule
RegisterEventListeners() []func(context.Context, protoiface.MessageV1)
RegisterEventInterceptors() []func(context.Context, protoiface.MessageV1) error
}

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It's just a more ergonomic API this way I think

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EventListenerRegistrar is just a dummy struct to make using generics easy

core/appmodule/event.go Outdated Show resolved Hide resolved
@aaronc aaronc mentioned this pull request Jan 23, 2023
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@aaronc aaronc changed the title feat(core): add event listener API feat(core): specify event listener API Jan 23, 2023
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Some questions about usage of any  instead of an interface

// RegisterEventListener registers an event listener for event type E. If a non-nil error is returned by the listener,
// it will cause the process which emitted the event to fail.
func RegisterEventListener[E protoiface.MessageV1](registrar *EventListenerRegistrar, listener func(context.Context, E) error) {
registrar.listeners = append(registrar.listeners, listener)
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why not this instead of using []any.

Suggested change
registrar.listeners = append(registrar.listeners, listener)
listenerF := func(ctx context.Context, iMsg protoiface.MessageV1) error {
concrete, ok := iMsg.(E)
if !ok { return fmt.Errorf("...")
return listener(ctx, concrete)
}
registrar.listeners = append(registrar.listeners, listenerF)

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Because the caller will be doing a type check anyway. I think this would just add extra type checking. Also in core we don't want to add any implementation details. This should be defer all those details to runtime


// EventListenerRegistrar allows registering event listeners.
type EventListenerRegistrar struct {
listeners []any
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Suggested change
listeners []any
listeners []func(ctx context.Context, iMsg protoiface.MessageV1) error

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aaronc commented Jan 24, 2023

Are we okay to merge this? I think this should have a standalone ADR by the way. I can work on that after #12972.

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aaronc commented Jan 24, 2023

I'm taking the 👍 as a yes

@aaronc aaronc enabled auto-merge (squash) January 24, 2023 17:22
@aaronc aaronc merged commit e822585 into main Jan 24, 2023
@aaronc aaronc deleted the aaronc/core-api-event-listeners branch January 24, 2023 17:41
@coderabbitai coderabbitai bot mentioned this pull request May 3, 2024
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5 participants