add ci conf and subscribe hook for the AsyncTopic

.gitignore

@@ -0,0 +1 @@
+*.out

.gitlab-ci.yml

@@ -0,0 +1,13 @@
+image: golang:latest
+
+stages:
+  - test
+
+format:
+  stage: test
+  script:
+    - go fmt gitlab.com/naterciom/gubgub
+    - go vet gitlab.com/naterciom/gubgub
+    - go test -race gitlab.com/naterciom/gubgub
+
+

async.go

@@ -20,7 +20,8 @@ type AsyncTopic[T any] struct {
 // NewAsyncTopic creates a Topic that publishes messages asynchronously.
 func NewAsyncTopic[T any](ctx context.Context, opts ...AsyncTopicOption) *AsyncTopic[T] {
 	options := AsyncTopicOptions{
-		onClose: func() {},
+		onClose:     func() {},
+		onSubscribe: func(count int) {},
 	}
 
 	for _, opt := range opts {
@@ -52,6 +53,7 @@ func (t *AsyncTopic[T]) run(ctx context.Context) {
 
 		case newCallback := <-t.subscribeCh:
 			subscribers = append(subscribers, newCallback)
+			t.options.onSubscribe(len(subscribers))
 
 		case msg := <-t.publishCh:
 			keepers := make([]Subscriber[T], 0, len(subscribers))
@@ -88,7 +90,6 @@ func (t *AsyncTopic[T]) Subscribe(fn Subscriber[T]) error {
 
 	if t.closed {
 		return fmt.Errorf("async topic subscribe: %w", ErrTopicClosed)
-		//	return nil
 	}
 
 	t.subscribeCh <- fn
@@ -104,13 +105,20 @@ func (t *AsyncTopic[T]) close() {
 }
 
 type AsyncTopicOptions struct {
-	onClose func()
+	onClose     func()
+	onSubscribe func(count int)
 }
 
 type AsyncTopicOption func(*AsyncTopicOptions)
 
 func WithOnClose(fn func()) AsyncTopicOption {
-	return func(a *AsyncTopicOptions) {
-		a.onClose = fn
+	return func(opts *AsyncTopicOptions) {
+		opts.onClose = fn
+	}
+}
+
+func WithOnSubscribe(fn func(count int)) AsyncTopicOption {
+	return func(opts *AsyncTopicOptions) {
+		opts.onSubscribe = fn
 	}
 }

async_test.go

@@ -107,6 +107,34 @@ func TestAsyncTopic_WithOnClose(t *testing.T) {
 	}
 }
 
+func TestAsyncTopic_WithOnSubscribe(t *testing.T) {
+	const totalSub = 10
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	feedback := make(chan int, totalSub)
+	defer close(feedback)
+
+	topic := NewAsyncTopic[int](ctx, WithOnSubscribe(func(count int) { feedback <- count }))
+
+	for range totalSub {
+		topic.Subscribe(func(i int) bool { return true })
+	}
+
+	count := 0
+	for count < totalSub {
+		select {
+		case c := <-feedback:
+			count++
+			assert.Equal(t, count, c, "expected %d but got %d instead", count, c)
+
+		case <-time.After(time.Second):
+			t.Fatalf("expected %d feedback items by now but only got %d", totalSub, count)
+		}
+	}
+}
+
 func TestAsyncTopic_SubscribeClosedTopicError(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()