Check native sliding sync support against an unstable feature flag

src/SlidingSyncManager.ts

@@ -372,26 +372,17 @@
  }
 
  /**
- * Check if the server "natively" supports sliding sync (at the unstable endpoint).
+ * Check if the server "natively" supports sliding sync (with an unstable endpoint).
  * @param client The MatrixClient to use
- * @return Whether the "native" (unstable) endpoint is up
+ * @return Whether the "native" (unstable) endpoint is supported
  */
  public async nativeSlidingSyncSupport(client: MatrixClient): Promise<boolean> {
- try {
- // We use OPTIONS to avoid causing a real sync to happen, as that may be intensive or encourage
- // middleware software to start polling as our access token (thus stealing our to-device messages).
- // See https://github.com/element-hq/element-web/issues/27426
- // XXX: Using client.http is a bad thing - it's meant to be private access. See `client.http` for details.
- await client.http.authedRequest<void>(Method.Options, "/sync", undefined, undefined, {
- localTimeoutMs: 10 * 1000, // 10s
- prefix: "/_matrix/client/unstable/org.matrix.msc3575",
- });
- } catch (e) {
- return false; // 404, M_UNRECOGNIZED
+ // Per https://github.com/matrix-org/matrix-spec-proposals/pull/3575/files#r1589542561
+ const support = await client.doesServerSupportUnstableFeature("org.matrix.msc3575");
+ if (support) {
+ logger.log("nativeSlidingSyncSupport: sliding sync advertised as unstable");
  }
-
- logger.log("nativeSlidingSyncSupport: sliding sync endpoint is up");
- return true; // 200, OK
+ return support;
  }
 
  /**

test/SlidingSyncManager-test.ts

@@ -16,8 +16,7 @@ limitations under the License.
 
 import { SlidingSync } from "matrix-js-sdk/src/sliding-sync";
 import { mocked } from "jest-mock";
-import { IRequestOpts, MatrixClient, MatrixEvent, Method, Room } from "matrix-js-sdk/src/matrix";
-import { QueryDict } from "matrix-js-sdk/src/utils";
+import { MatrixClient, MatrixEvent, Room } from "matrix-js-sdk/src/matrix";
 
 import { SlidingSyncManager } from "../src/SlidingSyncManager";
 import { stubClient } from "./test-utils";
@@ -261,41 +260,18 @@ describe("SlidingSyncManager", () => {
  it("should make an OPTIONS request to avoid unintended side effects", async () => {
  // See https://github.com/element-hq/element-web/issues/27426
 
- // Developer note: We mock this in a truly terrible way because of how the call is done. There's not
- // really much we can do to avoid it.
- client.http = {
- async authedRequest(
- method: Method,
- path: string,
- queryParams?: QueryDict,
- body?: Body,
- paramOpts: IRequestOpts & {
- doNotAttemptTokenRefresh?: boolean;
- } = {},
- ): Promise<any> {
- // XXX: Ideally we'd use ResponseType<> like in the real thing, but it's not exported
- expect(method).toBe(Method.Options);
- expect(path).toBe("/sync");
- expect(queryParams).toBeUndefined();
- expect(body).toBeUndefined();
- expect(paramOpts).toEqual({
- localTimeoutMs: 10 * 1000, // 10s
- prefix: "/_matrix/client/unstable/org.matrix.msc3575",
- });
- return {};
- },
- } as any;
-
+ const unstableSpy = jest
+ .spyOn(client, "doesServerSupportUnstableFeature")
+ .mockImplementation(async (feature: string) => {
+ expect(feature).toBe("org.matrix.msc3575");
+ return true;
+ });
  const proxySpy = jest.spyOn(manager, "getProxyFromWellKnown").mockResolvedValue("proxy");
 
  expect(SlidingSyncController.serverSupportsSlidingSync).toBeFalsy();
-
  await manager.checkSupport(client); // first thing it does is call nativeSlidingSyncSupport
-
- // Note: if this expectation is failing, it may mean the authedRequest mock threw an expectation failure
- // which got consumed by `nativeSlidingSyncSupport`. Log your errors to discover more.
  expect(proxySpy).not.toHaveBeenCalled();
-
+ expect(unstableSpy).toHaveBeenCalled();
  expect(SlidingSyncController.serverSupportsSlidingSync).toBeTruthy();
  });
  });