Extra worklet module loading and mock it in tests

jest.config.ts

@@ -33,7 +33,7 @@ const config: Config = {
         "waveWorker\\.min\\.js": "<rootDir>/__mocks__/empty.js",
         "workers/(.+)Factory": "<rootDir>/__mocks__/workerFactoryMock.js",
         "^!!raw-loader!.*": "jest-raw-loader",
-        "RecorderWorklet": "<rootDir>/__mocks__/empty.js",
+        "recorderWorkletFactory": "<rootDir>/__mocks__/empty.js",
     },
     transformIgnorePatterns: ["/node_modules/(?!matrix-js-sdk).+$"],
     collectCoverageFrom: [

src/audio/VoiceRecording.ts

@@ -28,11 +28,7 @@ import { UPDATE_EVENT } from "../stores/AsyncStore";
 import { createAudioContext } from "./compat";
 import { FixedRollingArray } from "../utils/FixedRollingArray";
 import { clamp } from "../utils/numbers";
-// This import is needed for dead code analysis but not actually used because the
-// built-in worker / worklet handling in Webpack 5 only supports static paths
-// @ts-ignore no-unused-locals
-// eslint-disable-next-line @typescript-eslint/no-unused-vars
-import mxRecorderWorkletPath from "./RecorderWorklet";
+import recorderWorkletFactory from "./recorderWorkletFactory";
 
 const CHANNELS = 1; // stereo isn't important
 export const SAMPLE_RATE = 48000; // 48khz is what WebRTC uses. 12khz is where we lose quality.
@@ -133,12 +129,7 @@ export class VoiceRecording extends EventEmitter implements IDestroyable {
             if (this.recorderContext.audioWorklet) {
                 // Set up our worklet. We use this for timing information and waveform analysis: the
                 // web audio API prefers this be done async to avoid holding the main thread with math.
-
-                // The audioWorklet.addModule syntax is required for Webpack 5 to correctly recognise
-                // this as a worklet rather than an asset. This also requires the parser.javascript.worker
-                // configuration described in https://github.com/webpack/webpack.js.org/issues/6869.
-                const audioWorklet = this.recorderContext.audioWorklet;
-                await audioWorklet.addModule(new URL("./RecorderWorklet.ts", import.meta.url));
+                await recorderWorkletFactory(this.recorderContext);
 
                 this.recorderWorklet = new AudioWorkletNode(this.recorderContext, WORKLET_NAME);
                 this.recorderSource.connect(this.recorderWorklet);

src/audio/recorderWorkletFactory.ts

@@ -0,0 +1,28 @@
+/*
+Copyright 2023 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// This import is needed for dead code analysis but not actually used because the
+// built-in worker / worklet handling in Webpack 5 only supports static paths
+// @ts-ignore no-unused-locals
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+import mxRecorderWorkletPath from "./RecorderWorklet";
+
+export default function recorderWorkletFactory(context: AudioContext): Promise<void> {
+  // The context.audioWorklet.addModule syntax is required for Webpack 5 to correctly recognise
+  // this as a worklet rather than an asset. This also requires the parser.javascript.worker
+  // configuration described in https://github.com/webpack/webpack.js.org/issues/6869.
+  return context.audioWorklet.addModule(new URL("./RecorderWorklet.ts", import.meta.url));
+}