stream: have SnapshotFunc accept a non-pointer SubscribeRequest

The value is not expected to be modified. Passing a value makes that explicit.

agent/consul/state/store_integration_test.go

@@ -376,7 +376,7 @@ var topicService stream.Topic = topic("test-topic-service")
 
 func newTestSnapshotHandlers(s *Store) stream.SnapshotHandlers {
 	return stream.SnapshotHandlers{
-		topicService: func(req *stream.SubscribeRequest, snap stream.SnapshotAppender) (uint64, error) {
+		topicService: func(req stream.SubscribeRequest, snap stream.SnapshotAppender) (uint64, error) {
 			idx, nodes, err := s.ServiceNodes(nil, req.Key, nil)
 			if err != nil {
 				return idx, err

agent/consul/stream/event_publisher.go

@@ -61,7 +61,11 @@ type changeEvents struct {
 // SnapshotHandlers is a mapping of Topic to a function which produces a snapshot
 // of events for the SubscribeRequest. Events are appended to the snapshot using SnapshotAppender.
 // The nil Topic is reserved and should not be used.
-type SnapshotHandlers map[Topic]func(*SubscribeRequest, SnapshotAppender) (index uint64, err error)
+type SnapshotHandlers map[Topic]SnapshotFunc
+
+// SnapshotFunc builds a snapshot for the subscription request, and appends the
+// events to the Snapshot using SnapshotAppender.
+type SnapshotFunc func(SubscribeRequest, SnapshotAppender) (index uint64, err error)
 
 // SnapshotAppender appends groups of events to create a Snapshot of state.
 type SnapshotAppender interface {

agent/consul/stream/event_publisher_test.go

@@ -58,7 +58,7 @@ func TestEventPublisher_PublishChangesAndSubscribe_WithSnapshot(t *testing.T) {
 
 func newTestSnapshotHandlers() SnapshotHandlers {
 	return SnapshotHandlers{
-		testTopic: func(req *SubscribeRequest, buf SnapshotAppender) (uint64, error) {
+		testTopic: func(req SubscribeRequest, buf SnapshotAppender) (uint64, error) {
 			if req.Topic != testTopic {
 				return 0, fmt.Errorf("unexpected topic: %v", req.Topic)
 			}
@@ -117,7 +117,7 @@ func TestEventPublisher_ShutdownClosesSubscriptions(t *testing.T) {
 	t.Cleanup(cancel)
 
 	handlers := newTestSnapshotHandlers()
-	fn := func(req *SubscribeRequest, buf SnapshotAppender) (uint64, error) {
+	fn := func(req SubscribeRequest, buf SnapshotAppender) (uint64, error) {
 		return 0, nil
 	}
 	handlers[intTopic(22)] = fn

agent/consul/stream/event_snapshot.go

@@ -18,8 +18,6 @@ type eventSnapshot struct {
 	snapBuffer *eventBuffer
 }
 
-type snapFunc func(req *SubscribeRequest, buf SnapshotAppender) (uint64, error)
-
 // newEventSnapshot creates a snapshot buffer based on the subscription request.
 // The current buffer head for the topic requested is passed so that once the
 // snapshot is complete and has been delivered into the buffer, any events
@@ -27,7 +25,7 @@ type snapFunc func(req *SubscribeRequest, buf SnapshotAppender) (uint64, error)
 // missed. Once the snapshot is delivered the topic buffer is spliced onto the
 // snapshot buffer so that subscribers will naturally follow from the snapshot
 // to wait for any subsequent updates.
-func newEventSnapshot(req *SubscribeRequest, topicBufferHead *bufferItem, fn snapFunc) *eventSnapshot {
+func newEventSnapshot(req *SubscribeRequest, topicBufferHead *bufferItem, fn SnapshotFunc) *eventSnapshot {
 	buf := newEventBuffer()
 	s := &eventSnapshot{
 		Head:       buf.Head(),
@@ -35,7 +33,7 @@ func newEventSnapshot(req *SubscribeRequest, topicBufferHead *bufferItem, fn sna
 	}
 
 	go func() {
-		idx, err := fn(req, s.snapBuffer)
+		idx, err := fn(*req, s.snapBuffer)
 		if err != nil {
 			s.snapBuffer.AppendItem(&bufferItem{Err: err})
 			return

agent/consul/stream/event_snapshot_test.go

@@ -161,8 +161,8 @@ func genSequentialIDs(start, end int) []string {
 	return ids
 }
 
-func testHealthConsecutiveSnapshotFn(size int, index uint64) snapFunc {
-	return func(req *SubscribeRequest, buf SnapshotAppender) (uint64, error) {
+func testHealthConsecutiveSnapshotFn(size int, index uint64) SnapshotFunc {
+	return func(req SubscribeRequest, buf SnapshotAppender) (uint64, error) {
 		for i := 0; i < size; i++ {
 			// Event content is arbitrary we are just using Health because it's the
 			// first type defined. We just want a set of things with consecutive