Merge pull request #393 from matrix-org/kegan/sync-accumulator-limited

Handle 'limited' timeline responses in the SyncAccumulator

spec/unit/sync-accumulator.spec.js

@@ -141,6 +141,41 @@ describe("SyncAccumulator", function() {
         expect(output.timeline.prev_batch).toEqual("pinned_to_8");
     });
 
+    it("should remove the stored timeline on limited syncs", () => {
+        sa.accumulate(syncSkeleton({
+            state: { events: [member("alice", "join")] },
+            timeline: {
+                events: [
+                    msg("alice", "1"),
+                    msg("alice", "2"),
+                    msg("alice", "3"),
+                ],
+                prev_batch: "pinned_to_1",
+            },
+        }));
+        // some time passes and now we get a limited sync
+        sa.accumulate(syncSkeleton({
+            state: { events: [] },
+            timeline: {
+                limited: true,
+                events: [
+                    msg("alice", "51"),
+                    msg("alice", "52"),
+                    msg("alice", "53"),
+                ],
+                prev_batch: "pinned_to_51",
+            },
+        }));
+
+        const output = sa.getJSON().roomsData.join["!foo:bar"];
+
+        expect(output.timeline.events.length).toEqual(3);
+        output.timeline.events.forEach((e, i) => {
+            expect(e.content.body).toEqual(""+(i+51));
+        });
+        expect(output.timeline.prev_batch).toEqual("pinned_to_51");
+    });
+
     it("should drop typing notifications", () => {
         const res = syncSkeleton({
             ephemeral: {

src/sync-accumulator.js

@@ -290,6 +290,12 @@ class SyncAccumulator {
             });
         }
 
+        // if we got a limited sync, we need to remove all timeline entries or else
+        // we will have gaps in the timeline.
+        if (data.timeline && data.timeline.limited) {
+            currentData._timeline = [];
+        }
+
         // Work out the current state. The deltas need to be applied in the order:
         // - existing state which didn't come down /sync.
         // - State events under the 'state' key.