Differentiate file suffixes between channel messages and conversations

src/internal/m365/collection/groups/backup_test.go

@@ -61,6 +61,11 @@ func (bh mockBackupHandler) augmentItemInfo(
 	// no-op
 }
 
+//lint:ignore U1000 false linter issue due to generics
+func (bh mockBackupHandler) supportsItemMetadata() bool {
+	return false
+}
+
 func (bh mockBackupHandler) canMakeDeltaQueries() bool {
 	return true
 }

src/internal/m365/collection/groups/channel_handler.go

@@ -125,6 +125,12 @@ func (bh channelsBackupHandler) augmentItemInfo(
 	// no-op
 }
 
+//lint:ignore U1000 false linter issue due to generics
+func (bh channelsBackupHandler) supportsItemMetadata() bool {
+	// No .data and .meta files for channel messages
+	return false
+}
+
 func channelContainer(ch models.Channelable) container[models.Channelable] {
 	return container[models.Channelable]{
 		storageDirFolders:   path.Elements{ptr.Val(ch.GetId())},

src/internal/m365/collection/groups/collection.go

@@ -348,8 +348,12 @@ func (col *lazyFetchCollection[C, I]) streamItems(ctx context.Context, errs *fau
 			// deleted items in a conversation. It might be added in the future
 			// if graph supports it, so make sure we put up both .data and .meta
 			// files for deletions.
-			col.stream <- data.NewDeletedItem(id + metadata.DataFileSuffix)
-			col.stream <- data.NewDeletedItem(id + metadata.MetaFileSuffix)
+			if col.getAndAugment.supportsItemMetadata() {
+				col.stream <- data.NewDeletedItem(id + metadata.DataFileSuffix)
+				col.stream <- data.NewDeletedItem(id + metadata.MetaFileSuffix)
+			} else {
+				col.stream <- data.NewDeletedItem(id)
+			}
 
 			atomic.AddInt64(&streamedItems, 1)
 			col.Counter.Inc(count.StreamItemsRemoved)
@@ -378,6 +382,10 @@ func (col *lazyFetchCollection[C, I]) streamItems(ctx context.Context, errs *fau
 				"item_id", id,
 				"parent_path", path.LoggableDir(col.LocationPath().String()))
 
+			// Conversation posts carry a .data suffix, while channel messages
+			// don't have any suffix. Metadata files are only supported for conversations.
+			dataFile := id
+
 			// Handle metadata before data so that if metadata file fails,
 			// we are not left with an orphaned data file.
 			//
@@ -396,15 +404,14 @@ func (col *lazyFetchCollection[C, I]) streamItems(ctx context.Context, errs *fau
 			if err != nil && !errors.Is(err, errMetadataFilesNotSupported) {
 				errs.AddRecoverable(ctx, clues.StackWC(ctx, err))
 
-				return
-			}
+					return
+				}
 
-			if err == nil {
 				// Skip adding progress reader for metadata files. It doesn't add
 				// much value.
 				storeItem, err := data.NewPrefetchedItem(
 					itemMeta,
-					id+metadata.MetaFileSuffix,
+					metaFile,
 					// Use the same last modified time as post's.
 					modTime)
 				if err != nil {
@@ -422,12 +429,12 @@ func (col *lazyFetchCollection[C, I]) streamItems(ctx context.Context, errs *fau
 					modTime:       modTime,
 					getAndAugment: col.getAndAugment,
 					resourceID:    col.protectedResource,
-					itemID:        id,
+					itemID:        dataFile,
 					containerIDs:  col.FullPath().Folders(),
 					contains:      col.contains,
 					parentPath:    col.LocationPath().String(),
 				},
-				id+metadata.DataFileSuffix,
+				dataFile,
 				modTime,
 				col.Counter,
 				el)

src/internal/m365/collection/groups/collection_test.go

@@ -180,6 +180,11 @@ func (getAndAugmentChannelMessage) augmentItemInfo(*details.GroupsInfo, models.C
 	// no-op
 }
 
+//lint:ignore U1000 false linter issue due to generics
+func (getAndAugmentChannelMessage) supportsItemMetadata() bool {
+	return false
+}
+
 func (suite *CollectionUnitSuite) TestPrefetchCollection_streamItems() {
 	var (
 		t             = suite.T()
@@ -322,6 +327,11 @@ func (m *getAndAugmentConversation) augmentItemInfo(*details.GroupsInfo, models.
 	// no-op
 }
 
+//lint:ignore U1000 false linter issue due to generics
+func (m *getAndAugmentConversation) supportsItemMetadata() bool {
+	return true
+}
+
 func (m *getAndAugmentConversation) check(t *testing.T, expected []string) {
 	// Sort before comparing. We could use a set, but that would prevent us from
 	// detecting duplicates.

src/internal/m365/collection/groups/conversation_handler.go

@@ -170,6 +170,11 @@ func (bh conversationsBackupHandler) augmentItemInfo(
 	dgi.Post.Topic = ptr.Val(c.GetTopic())
 }
 
+//lint:ignore U1000 false linter issue due to generics
+func (bh conversationsBackupHandler) supportsItemMetadata() bool {
+	return true
+}
+
 func conversationThreadContainer(
 	c models.Conversationable,
 	t models.ConversationThreadable,

src/internal/m365/collection/groups/handlers.go

@@ -36,6 +36,7 @@ type getItemAndAugmentInfoer[C graph.GetIDer, I groupsItemer] interface {
 	getItemer[I]
 	getItemMetadataer[C, I]
 	augmentItemInfoer[C]
+	supportsItemMetadataer[C, I]
 }
 
 type augmentItemInfoer[C graph.GetIDer] interface {
@@ -60,6 +61,10 @@ type getItemMetadataer[C graph.GetIDer, I groupsItemer] interface {
 	) (io.ReadCloser, int, error)
 }
 
+type supportsItemMetadataer[C graph.GetIDer, I groupsItemer] interface {
+	supportsItemMetadata() bool
+}
+
 // gets all containers for the resource
 type getContainerser[C graph.GetIDer] interface {
 	getContainers(