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feat(core): specify event listener API #14735

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merged 6 commits into from
Jan 24, 2023
Merged

feat(core): specify event listener API #14735

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cf90c23
feat(core): add event listener API
aaronc Jan 23, 2023
82e6f5f
add test
aaronc Jan 23, 2023
14a8225
simplify API
aaronc Jan 23, 2023
a4b69fd
Merge branch 'main' into aaronc/core-api-event-listeners
aaronc Jan 23, 2023
25bb942
Merge branch 'main' into aaronc/core-api-event-listeners
aaronc Jan 24, 2023
d8669fd
Merge branch 'main' into aaronc/core-api-event-listeners
aaronc Jan 24, 2023
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32 changes: 32 additions & 0 deletions core/appmodule/event.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
package appmodule

import (
"context"

"google.golang.org/protobuf/runtime/protoiface"
)

// HasEventListeners is the extension interface that modules should implement to register
// event listeners.
type HasEventListeners interface {
AppModule

// RegisterEventListeners registers the module's events listeners.
RegisterEventListeners(registrar *EventListenerRegistrar)
}
Comment on lines +11 to +16
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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


// EventListenerRegistrar allows registering event listeners.
type EventListenerRegistrar struct {
listeners []any
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@testinginprod testinginprod Jan 23, 2023 •
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Suggested change
listeners []any
listeners []func(ctx context.Context, iMsg protoiface.MessageV1) error

}

// GetListeners gets the event listeners that have been registered
func (e *EventListenerRegistrar) GetListeners() []any {
return e.listeners
}
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// 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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@testinginprod testinginprod Jan 23, 2023 •
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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

}
17 changes: 17 additions & 0 deletions core/appmodule/event_test.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
package appmodule

import (
"context"
"reflect"
"testing"

"github.com/stretchr/testify/require"
"google.golang.org/protobuf/types/known/timestamppb"
)

func TestEventListenerRegistrar(t *testing.T) {
registrar := &EventListenerRegistrar{}
RegisterEventListener(registrar, func(ctx context.Context, dummy *timestamppb.Timestamp) error { return nil })
require.Len(t, registrar.listeners, 1)
require.Equal(t, reflect.Func, reflect.TypeOf(registrar.listeners[0]).Kind())
}