Clarify why certain tests disable the React Compiler

With the React Compiler, our component code is transformed at build time to automatically apply various forms of memoization. This changes the runtime semantics of our code a little bit and therefore could surface new bugs in the next release cycle in case any components fail to follow the rules of React. See https://react.dev/learn/react-compiler for more information.

This results in a small bundle size increase and modest performance gains, but I think it's worth it given the potential for larger performance gains once we tune the component structure a bit more.

.github/workflows/test.yaml

@@ -7,10 +7,6 @@ jobs:
   vitest:
     name: Run unit tests
     runs-on: ubuntu-latest
-    container:
-      # Make sure to grab the latest version of the Playwright image
-      # https://playwright.dev/docs/docker#pull-the-image
-      image: mcr.microsoft.com/playwright:v1.61.1-noble
     steps:
       - name: Checkout code
         uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
@@ -26,6 +22,18 @@ jobs:
       - name: Install dependencies
         # ignore-pnpmfile should never be commited. Make CI crash if it happened (`pnpmfileChecksum` is present)
         run: "pnpm install --frozen-lockfile --ignore-pnpmfile"
+      - name: Get Playwright version
+        run: echo "PLAYWRIGHT_VERSION=$(pnpm list @playwright/test --depth=0 --json | jq -r '.[0].devDependencies["@playwright/test"].version')" >> $GITHUB_ENV
+      - name: Cache Playwright binaries
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6
+        id: playwright-cache
+        with:
+          path: |
+            ~/.cache/ms-playwright
+          key: ${{ runner.os }}-playwright-${{ env.PLAYWRIGHT_VERSION }}
+      - name: Install Playwright binaries
+        if: steps.playwright-cache.outputs.cache-hit != 'true'
+        run: pnpm playwright install --with-deps
       - name: Vitest
         run: "pnpm run test:coverage"
       - name: Upload to codecov
@@ -52,8 +60,18 @@ jobs:
       - name: Install dependencies
         # ignore-pnpmfile should never be commited. Make CI crash if it happened (`pnpmfileChecksum` is present)
         run: pnpm install --frozen-lockfile --ignore-pnpmfile
-      - name: Install Playwright Browsers
-        run: pnpm exec playwright install --with-deps
+      - name: Get Playwright version
+        run: echo "PLAYWRIGHT_VERSION=$(pnpm list @playwright/test --depth=0 --json | jq -r '.[0].devDependencies["@playwright/test"].version')" >> $GITHUB_ENV
+      - name: Cache Playwright binaries
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6
+        id: playwright-cache
+        with:
+          path: |
+            ~/.cache/ms-playwright
+          key: ${{ runner.os }}-playwright-${{ env.PLAYWRIGHT_VERSION }}
+      - name: Install Playwright binaries
+        if: steps.playwright-cache.outputs.cache-hit != 'true'
+        run: pnpm playwright install --with-deps
       - name: Run backend components
         run: |
           docker compose -f docker-compose-dev.yml -f docker-compose-playwright.yml pull

docker-compose-dev.yml

@@ -47,7 +47,7 @@ services:
       - ecbackend
 
   livekit:
-    image: livekit/livekit-server:v1.10.1
+    image: livekit/livekit-server:v1.13.4
     pull_policy: always
     hostname: livekit-sfu
     command: --dev --config /etc/livekit.yaml
@@ -70,7 +70,7 @@ services:
       - ecbackend
 
   livekit-1:
-    image: livekit/livekit-server:v1.10.1
+    image: livekit/livekit-server:v1.13.4
     pull_policy: always
     hostname: livekit-sfu-1
     command: --dev --config /etc/livekit.yaml

docker-compose-playwright.yml

@@ -13,7 +13,7 @@ services:
       - ./backend/playwright_homeserver-othersite.yaml:/data/cfg/homeserver.yaml:Z
   element-web:
     # Pin to a SHA so that upstream cannot break our tests. Renovate handles regular updates.
-    image: ghcr.io/element-hq/element-web:develop@sha256:d1841828a390d96da2ee64232949db641f11766fb506ec561374819d10533b9a
+    image: ghcr.io/element-hq/element-web:develop@sha256:0183c0a7f4292252349ddcff2de92a83a4571b283da49cc54adb9efbf3d20695
   element-web-1:
     # Pin to a SHA so that upstream cannot break our tests. Renovate handles regular updates.
-    image: ghcr.io/element-hq/element-web:develop@sha256:d1841828a390d96da2ee64232949db641f11766fb506ec561374819d10533b9a
+    image: ghcr.io/element-hq/element-web:develop@sha256:0183c0a7f4292252349ddcff2de92a83a4571b283da49cc54adb9efbf3d20695

docs/self_hosting.md

@@ -86,10 +86,11 @@ to implement
 In the context of MatrixRTC, we suggest using a single hostname for backend
 communication by implementing endpoint routing within a reverse proxy setup. For
 the example above, this results in:
-| Service | Endpoint | Example |
-| -------- | ------- | ------- |
+
+| Service                                                                           | Endpoint       | Example                              |
+| --------------------------------------------------------------------------------- | -------------- | ------------------------------------ |
 | [Livekit SFU](https://github.com/livekit/livekit) WebSocket signalling connection | `/livekit/sfu` | `matrix-rtc.example.com/livekit/sfu` |
-| [MatrixRTC Authorization Service](https://github.com/element-hq/lk-jwt-service) | `/livekit/jwt` | `matrix-rtc.example.com/livekit/jwt` |
+| [MatrixRTC Authorization Service](https://github.com/element-hq/lk-jwt-service)   | `/livekit/jwt` | `matrix-rtc.example.com/livekit/jwt` |
 
 Using Nginx, you can achieve this by:
 

package.json

@@ -54,6 +54,7 @@
     "@radix-ui/react-slider": "^1.1.2",
     "@radix-ui/react-visually-hidden": "^1.0.3",
     "@react-spring/web": "^10.0.0",
+    "@rolldown/plugin-babel": "^0.2.3",
     "@sentry/react": "^8.0.0",
     "@sentry/vite-plugin": "^3.0.0",
     "@storybook/addon-docs": "^10.3.6",
@@ -80,7 +81,8 @@
     "@vitejs/plugin-react": "^6.0.2",
     "@vitest/browser-playwright": "^4.1.5",
     "@vitest/coverage-v8": "^4.0.18",
-    "@vitest/ui": "4.1.9",
+    "@vitest/ui": "4.1.10",
+    "babel-plugin-react-compiler": "^1.0.0",
     "classnames": "^2.3.1",
     "copy-to-clipboard": "^3.3.3",
     "eslint-plugin-element-call": "link:eslint",
@@ -99,9 +101,9 @@
     "node-stdlib-browser": "^1.3.1",
     "normalize.css": "^8.0.1",
     "observable-hooks": "^4.2.3",
-    "oxfmt": "^0.56.0",
+    "oxfmt": "^0.61.0",
     "oxlint": "^1.70.0",
-    "oxlint-tsgolint": "^0.23.0",
+    "oxlint-tsgolint": "^0.25.0",
     "pako": "^2.0.4",
     "postcss": "^8.4.41",
     "postcss-preset-env": "^10.0.0",

playwright/widget/pip-call-button-interaction.test.ts

@@ -36,6 +36,7 @@ widgetTest("Footer interaction in PiP", async ({ addUser, browserName }) => {
   await valere.page.waitForTimeout(600);
 
   // Switch to the other room, the call should go to PIP
+  await TestHelpers.expandRoomList(valere.page);
   await TestHelpers.switchToRoomNamed(valere.page, "OtherRoom");
 
   // We should see the PIP overlay

playwright/widget/pip-call.test.ts

@@ -53,6 +53,7 @@ widgetTest("Put call in PIP", async ({ addUser, browserName }) => {
   });
 
   // Switch to the other room, the call should go to PIP
+  await TestHelpers.expandRoomList(valere.page);
   await TestHelpers.switchToRoomNamed(valere.page, "DoubleTask");
 
   // We should see the PIP overlay

playwright/widget/test-helpers.ts

@@ -346,6 +346,12 @@ export class TestHelpers {
     }
   }
 
+  public static async expandRoomList(page: Page): Promise<void> {
+    await page
+      .getByRole("separator", { name: "Click or drag to expand" })
+      .click();
+  }
+
   /**
    * Switches to a room in the room list by its name.
    * @param page - The EW page

src/index.css

@@ -15,8 +15,7 @@ Please see LICENSE in the repository root for full details.
 @import url("@fontsource/inconsolata/700.css");
 
 @import url("normalize.css/normalize.css") layer(normalize);
-@import url("@vector-im/compound-design-tokens/assets/web/css/compound-design-tokens.css")
-layer(compound);
+@import url("@vector-im/compound-design-tokens/assets/web/css/compound-design-tokens.css") layer(compound);
 @import url("@vector-im/compound-web/dist/style.css") layer(compound.components);
 
 :root {

src/livekit/MatrixAudioRenderer.test.tsx

@@ -99,7 +99,7 @@ function renderTestComponent(
     ),
   } as unknown as Room;
 
-  if (explicitTracks?.length ?? 0 > 0) {
+  if ((explicitTracks?.length ?? 0) > 0) {
     tracks = explicitTracks!.map(({ participantId, source, kind }) => {
       const participant =
         liveKitParticipants.find((p) => p.identity === participantId) ??

src/tile/SpotlightTile.test.tsx

@@ -32,6 +32,7 @@ import {
 global.IntersectionObserver = class MockIntersectionObserver {
   public observe(): void {}
   public unobserve(): void {}
+  public disconnect(): void {}
 } as unknown as typeof IntersectionObserver;
 
 test("SpotlightTile is accessible", async () => {

src/useEvents.test.tsx

@@ -28,6 +28,10 @@ test("useTypedEventEmitterState reacts to events", async () => {
   const emitter = new TestEmitter();
 
   const Test: FC = () => {
+    // Disable the React Compiler to work around the following bug:
+    // https://github.com/react/react/issues/34901
+    "use no memo";
+
     const value = useTypedEventEmitterState(
       emitter,
       "change",
@@ -51,6 +55,10 @@ test("useTypedEventEmitterState reacts to changes made by an effect mounted on t
   const emitter = new TestEmitter();
 
   const Test: FC = () => {
+    // Disable the React Compiler to work around the following bug:
+    // https://github.com/react/react/issues/34901
+    "use no memo";
+
     useEffect(() => emitter.setState(2), []);
     const value = useTypedEventEmitterState(
       emitter,
@@ -69,6 +77,10 @@ test("useTypedEventEmitterState reacts to changes in getState", async () => {
   const emitter = new TestEmitter();
 
   const Test: FC = () => {
+    // Disable the React Compiler to work around the following bug:
+    // https://github.com/react/react/issues/34901
+    "use no memo";
+
     const [fn, setFn] = useState(() => emitter.getState);
     const value = useTypedEventEmitterState(emitter, "change", fn);
     return (

vite.config.ts

@@ -7,7 +7,7 @@ Please see LICENSE in the repository root for full details.
 
 import {
   loadEnv,
-  PluginOption,
+  type PluginOption,
   searchForWorkspaceRoot,
   type ConfigEnv,
   type UserConfig,
@@ -19,8 +19,8 @@ import { codecovVitePlugin } from "@codecov/vite-plugin";
 import { sentryVitePlugin } from "@sentry/vite-plugin";
 import { nodePolyfills } from "vite-plugin-node-polyfills";
 import wasm from "vite-plugin-wasm";
-
-import react from "@vitejs/plugin-react";
+import babel from "@rolldown/plugin-babel";
+import react, { reactCompilerPreset } from "@vitejs/plugin-react";
 import { realpathSync } from "fs";
 import * as fs from "node:fs";
 
@@ -29,6 +29,9 @@ export const vitePluginsConfig = ({
 }: Pick<ConfigEnv, "mode">): UserConfig => {
   const env = loadEnv(mode, process.cwd());
   const plugins: PluginOption[] = [
+    babel({
+      presets: [reactCompilerPreset()],
+    }),
     react(),
     wasm(),
     nodePolyfills({