Refactoring type 'Handler' to an interface.

Primarily, this is a future-proofing operation to protect in the case of having super-set contracts over Handle Message.

handler.go

@@ -0,0 +1,18 @@
+package servicebus
+
+import "context"
+
+type (
+	// Handler exposes the functionality required to process a Service Bus message.
+	Handler interface {
+		Handle(context.Context, *Message) DispositionAction
+	}
+
+	// HandlerFunc is a type converter that allows a func to be used as a `Handler`
+	HandlerFunc func(context.Context, *Message) DispositionAction
+)
+
+// Handle redirects this call to the func that was provided.
+func (hf HandlerFunc) Handle(ctx context.Context, msg *Message) DispositionAction {
+	return hf(ctx, msg)
+}

message.go

@@ -58,9 +58,6 @@ type (
 	// DispositionAction represents the action to notify Azure Service Bus of the Message's disposition
 	DispositionAction func(ctx context.Context)
 
-	// Handler is the function signature for any receiver of AMQP messages
-	Handler func(context.Context, *Message) DispositionAction
-
 	// MessageErrorCondition represents a well-known collection of AMQP errors
 	MessageErrorCondition string
 

package_examples_test.go

@@ -40,11 +40,13 @@ func Example_helloWorld() {
 	go func(ctx context.Context, client *servicebus.Queue, quitAfter int) {
 		received := make(chan struct{})
 
-		listenHandle, err := client.Receive(ctx, func(ctx context.Context, message *servicebus.Message) servicebus.DispositionAction {
-			fmt.Println(string(message.Data))
-			received <- struct{}{}
-			return message.Complete()
-		})
+		listenHandle, err := client.Receive(
+			ctx,
+			servicebus.HandlerFunc(func(ctx context.Context, message *servicebus.Message) servicebus.DispositionAction {
+				fmt.Println(string(message.Data))
+				received <- struct{}{}
+				return message.Complete()
+			}))
 		if err != nil {
 			errs <- err
 			return

queue_test.go

@@ -471,8 +471,9 @@ func testRequeueOnFail(ctx context.Context, t *testing.T, q *Queue) {
 		wg.Add(2)
 		var receivedMsg *Message
 		fail := true
+
 		listenHandle, err := q.Receive(context.Background(),
-			func(ctx context.Context, msg *Message) DispositionAction {
+			HandlerFunc(func(ctx context.Context, msg *Message) DispositionAction {
 				receivedMsg = msg
 				defer func() {
 					wg.Done()
@@ -482,7 +483,8 @@ func testRequeueOnFail(ctx context.Context, t *testing.T, q *Queue) {
 					return msg.Abandon()
 				}
 				return msg.Complete()
-			})
+			}))
+
 		if assert.NoError(t, err) {
 			defer listenHandle.Close(ctx)
 			end, _ := ctx.Deadline()
@@ -501,13 +503,13 @@ func testMessageProperties(ctx context.Context, t *testing.T, q *Queue) {
 		wg.Add(1)
 		var receivedMsg *Message
 		listenHandle, err := q.Receive(context.Background(),
-			func(ctx context.Context, msg *Message) DispositionAction {
+			HandlerFunc(func(ctx context.Context, msg *Message) DispositionAction {
 				receivedMsg = msg
 				defer func() {
 					wg.Done()
 				}()
 				return msg.Complete()
-			})
+			}))
 		if assert.NoError(t, err) {
 			defer listenHandle.Close(ctx)
 			end, _ := ctx.Deadline()
@@ -549,12 +551,12 @@ func testQueueSendAndReceiveInOrder(ctx context.Context, t *testing.T, queue *Qu
 	wg.Add(numMessages)
 	// ensure in-order processing of messages from the queue
 	count := 0
-	listener, err := queue.Receive(ctx, func(ctx context.Context, event *Message) DispositionAction {
+	listener, err := queue.Receive(ctx, HandlerFunc(func(ctx context.Context, event *Message) DispositionAction {
 		assert.Equal(t, messages[count], string(event.Data))
 		count++
 		wg.Done()
 		return event.Complete()
-	})
+	}))
 	if assert.NoError(t, err) {
 		defer listener.Close(ctx)
 		end, _ := ctx.Deadline()
@@ -580,11 +582,11 @@ func testQueueSendAndReceiveScheduled(ctx context.Context, t *testing.T, queue *
 	if assert.NoError(t, queue.Send(ctx, msg)) {
 		var wg sync.WaitGroup
 		wg.Add(1)
-		listener, err := queue.Receive(ctx, func(ctx context.Context, received *Message) DispositionAction {
+		listener, err := queue.Receive(ctx, HandlerFunc(func(ctx context.Context, received *Message) DispositionAction {
 			defer wg.Done()
 			assert.WithinDuration(t, time.Now(), futureTime, buffer)
 			return received.Complete()
-		})
+		}))
 		if assert.NoError(t, err) {
 			defer listener.Close(ctx)
 			end, _ := ctx.Deadline()
@@ -617,7 +619,7 @@ func testDuplicateDetection(ctx context.Context, t *testing.T, queue *Queue) {
 	wg.Add(2)
 	received := make(map[interface{}]string)
 	var all []*Message
-	queue.Receive(ctx, func(ctx context.Context, message *Message) DispositionAction {
+	queue.Receive(ctx, HandlerFunc(func(ctx context.Context, message *Message) DispositionAction {
 		all = append(all, message)
 		if _, ok := received[message.ID]; !ok {
 			// caught a new one
@@ -631,7 +633,7 @@ func testDuplicateDetection(ctx context.Context, t *testing.T, queue *Queue) {
 			}
 		}
 		return message.Complete()
-	})
+	}))
 	end, _ := ctx.Deadline()
 	waitUntil(t, &wg, time.Until(end))
 }
@@ -679,12 +681,12 @@ func testQueueSendAndReceiveWithReceiveAndDelete(ctx context.Context, t *testing
 	var wg sync.WaitGroup
 	wg.Add(numMessages)
 	count := 0
-	queue.Receive(ctx, func(ctx context.Context, msg *Message) DispositionAction {
+	queue.Receive(ctx, HandlerFunc(func(ctx context.Context, msg *Message) DispositionAction {
 		assert.Equal(t, messages[count], string(msg.Data))
 		count++
 		wg.Done()
 		return nil
-	})
+	}))
 	end, _ := ctx.Deadline()
 	waitUntil(t, &wg, time.Until(end))
 }

receiver.go

@@ -193,7 +193,7 @@ func (r *receiver) handleMessage(ctx context.Context, msg *amqp.Message, handler
 	id := messageID(msg)
 	span.SetTag("amqp.message-id", id)
 
-	dispositionAction := handler(ctx, event)
+	dispositionAction := handler.Handle(ctx, event)
 
 	if r.mode == ReceiveAndDeleteMode {
 		return

subscription_test.go

@@ -275,10 +275,10 @@ func testSubscriptionReceive(ctx context.Context, t *testing.T, topic *Topic, su
 	if assert.NoError(t, topic.Send(ctx, NewMessageFromString("hello!"))) {
 		var wg sync.WaitGroup
 		wg.Add(1)
-		_, err := sub.Receive(ctx, func(eventCtx context.Context, msg *Message) DispositionAction {
+		_, err := sub.Receive(ctx, HandlerFunc(func(eventCtx context.Context, msg *Message) DispositionAction {
 			wg.Done()
 			return msg.Complete()
-		})
+		}))
 		if !assert.NoError(t, err) {
 			t.FailNow()
 		}