improved delivery tests

async.go

@@ -69,7 +69,6 @@ func (t *AsyncTopic[T]) run() {
 		select {
 		case newCallback, more := <-t.subscribeCh:
 			if !more {
-				// Ignore subscribeCh close. The publishCh will dictate when to exit this loop.
 				drainedSubscribe = true
 				break
 			}
@@ -79,7 +78,6 @@ func (t *AsyncTopic[T]) run() {
 
 		case msg, more := <-t.publishCh:
 			if !more {
-				// No more published messages, promise was fulfilled and we can return
 				drainedPublish = true
 				break
 			}
@@ -123,7 +121,7 @@ func (t *AsyncTopic[T]) Subscribe(fn Subscriber[T]) error {
 	return nil
 }
 
-// Feed allows you to for/range to consume future published messages. The supporting subscriber will eventually be discarded after you exit the for loop.
+// Feed allows the usage of for/range to consume future published messages. The supporting subscriber will eventually be discarded after you exit the for loop.
 func (t *AsyncTopic[T]) Feed() iter.Seq[T] {
 	feed := make(chan T, 1)
 	done := make(chan struct{})

delivery.go

@@ -1,7 +1,8 @@
 package gubgub
 
-// sequentialDelivery delivers a message to each subscriber sequentially. For performance reasons
+// sequentialDelivery effentiently delivers a message to each subscriber sequentially. For
-// this might mutate the subscribers slice inplace. Please overwrite it with the result of this
+// performance reasons this might mutate the subscribers slice inplace. Please overwrite it with
+// the result of this
 // call.
 func sequentialDelivery[T any](msg T, subscribers []Subscriber[T]) []Subscriber[T] {
 	last := len(subscribers) - 1

delivery_test.go

@@ -12,18 +12,18 @@ func TestSequentialDelivery(t *testing.T) {
 	feedback := make([]int, 0, 3)
 
 	subscribers := []Subscriber[int]{
-		func(i int) bool {
+		func(msg int) bool {
-			assert.Equalf(t, testMsg, i, "expected %d but got %d", testMsg, i)
+			assert.Equalf(t, testMsg, msg, "expected %d but got %d", testMsg, msg)
 			feedback = append(feedback, 1)
-			return true
-		},
-		func(i int) bool {
-			assert.Equalf(t, testMsg, i, "expected %d but got %d", testMsg, i)
-			feedback = append(feedback, 2)
 			return false
 		},
-		func(i int) bool {
+		func(msg int) bool {
-			assert.Equalf(t, testMsg, i, "expected %d but got %d", testMsg, i)
+			assert.Equalf(t, testMsg, msg, "expected %d but got %d", testMsg, msg)
+			feedback = append(feedback, 2)
+			return true
+		},
+		func(msg int) bool {
+			assert.Equalf(t, testMsg, msg, "expected %d but got %d", testMsg, msg)
 			feedback = append(feedback, 3)
 			return true
 		},
@@ -38,4 +38,25 @@ func TestSequentialDelivery(t *testing.T) {
 
 	assert.Len(t, finalSubscribers, len(nextSubscribers), "expected to have the same subscribers")
 	assert.Len(t, feedback, 5, "one or more subscriber was not called")
+
+	assertContainsExactlyN(t, 1, 1, feedback)
+	assertContainsExactlyN(t, 2, 2, feedback)
+	assertContainsExactlyN(t, 3, 2, feedback)
+}
+
+func assertContainsExactlyN[T comparable](t testing.TB, exp T, n int, slice []T) {
+	t.Helper()
+
+	var found int
+	for _, v := range slice {
+		if exp == v {
+			found++
+		}
+	}
+
+	if n > found {
+		t.Errorf("contains too few '%v': expected %d but found %d", exp, n, found)
+	} else if n < found {
+		t.Errorf("contains too many '%v': expected %d but found %d", exp, n, found)
+	}
 }

sync.go

@@ -2,8 +2,8 @@ package gubgub
 
 import "sync"
 
-// SyncTopic allows any message T to be broadcast to subscribers. Publishing and Subscribing
+// SyncTopic is the simplest and most naive topic. It allows any message T to be broadcast to
-// happens synchronously (block).
+// subscribers. Publishing and Subscribing happens synchronously (block).
 type SyncTopic[T any] struct {
 	mu          sync.Mutex
 	subscribers []Subscriber[T]
@@ -19,16 +19,7 @@ func (t *SyncTopic[T]) Publish(msg T) error {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
-	keepers := make([]Subscriber[T], 0, len(t.subscribers))
+	t.subscribers = sequentialDelivery(msg, t.subscribers)
-
-	for _, callback := range t.subscribers {
-		keep := callback(msg)
-		if keep {
-			keepers = append(keepers, callback)
-		}
-	}
-
-	t.subscribers = keepers
 
 	return nil
 }