Fix a second load() leaking a core, name a non-wasm wasmURL, types for TS < 4.4, rename the internal setTimeout

- load() on a loaded instance keeps its core (#494)
- a wasmURL serving HTML says which URL is wrong (#609)
- Callbacks is a Record, which TypeScript < 4.4 accepts (#701)
- bind.js no longer shadows the global setTimeout inside the core (#611)

Author: lucasgelfond

packages/ffmpeg/src/classes.ts

@@ -304,13 +304,10 @@ export class FFmpeg {
   public terminate = (): void => this.#terminate(ERROR_TERMINATED);
 
   #terminate = (reason: Error): void => {
-    const ids = Object.keys(this.#rejects);
     // rejects all incomplete Promises.
-    for (const id of ids) {
-      this.#rejects[id](reason);
-      delete this.#rejects[id];
-      delete this.#resolves[id];
-    }
+    Object.values(this.#rejects).forEach((reject) => reject(reason));
+    this.#rejects = {};
+    this.#resolves = {};
 
     if (this.#worker) {
       this.#worker.terminate();

packages/ffmpeg/src/types.ts

@@ -164,9 +164,7 @@ export type CallbackData =
   | FSNode[]
   | undefined;
 
-export interface Callbacks {
-  [id: number | string]: (data: CallbackData) => void;
-}
+export type Callbacks = Record<number, (data: CallbackData) => void>;
 
 export type LogEventCallback = (event: LogEvent) => void;
 export type ProgressEventCallback = (event: ProgressEvent) => void;

packages/ffmpeg/src/worker.ts

@@ -47,7 +47,9 @@ const load = async ({
   coreURL: _coreURL,
   wasmURL: _wasmURL,
 }: FFMessageLoadConfig): Promise<IsFirst> => {
-  const first = !ffmpeg;
+  // A second core would leak the first one's memory and threads (#494);
+  // terminate() and load() again to switch cores.
+  if (ffmpeg) return false;
 
   // ffmpeg-core runs FFmpeg's threads on a SharedArrayBuffer.
   if (typeof SharedArrayBuffer === "undefined") throw ERROR_NOT_ISOLATED;
@@ -77,9 +79,15 @@ const load = async ({
   // URL for _locateFile() in bind.js. In Node.js (file: URLs) emscripten
   // starts them from the core module itself and finds the wasm next to it.
   const mainScriptUrlOrBlob = `${coreURL}#${btoa(JSON.stringify({ wasmURL }))}`;
-  ffmpeg = await (self as WorkerGlobalScope).createFFmpegCore(
-    coreURL.startsWith("file:") ? {} : { mainScriptUrlOrBlob }
-  );
+  try {
+    ffmpeg = await (self as WorkerGlobalScope).createFFmpegCore(
+      coreURL.startsWith("file:") ? {} : { mainScriptUrlOrBlob }
+    );
+  } catch (e) {
+    // e.g. an HTML 404 page or SPA fallback served instead of the wasm (#609)
+    if (String(e).includes("magic word")) throw new Error(`${wasmURL} is not a WebAssembly file (${e})`);
+    throw e;
+  }
   ffmpeg.setLogger((data) =>
     self.postMessage({ type: FFMessageType.LOG, data })
   );
@@ -89,7 +97,7 @@ const load = async ({
       data,
     })
   );
-  return first;
+  return true;
 };
 
 const exec = ({ args, timeout = -1 }: FFMessageExecData): ExitCode => {

src/bind/ffmpeg/bind.js

@@ -83,7 +83,8 @@ function setLogger(logger) {
   Module["logger"] = logger;
 }
 
-function setTimeout(timeout) {
+// Not named setTimeout: that would shadow the global inside the core (#611).
+function setExecTimeout(timeout) {
   Module["timeout"] = timeout;
 }
 
@@ -134,7 +135,7 @@ Module["locateFile"] = _locateFile;
 Module["exec"] = exec;
 Module["ffprobe"] = ffprobe;
 Module["setLogger"] = setLogger;
-Module["setTimeout"] = setTimeout;
+Module["setTimeout"] = setExecTimeout;
 Module["setProgress"] = setProgress;
 Module["reset"] = reset;
 Module["terminateThreads"] = terminateThreads;

tests/ffmpeg/issues/494-double-load.test.js

@@ -4,7 +4,7 @@
 import { expect } from "vitest";
 import { test, coreURL } from "../../helpers/ffmpeg.js";
 
-test.fails("load() again keeps the loaded core (#494)", { timeout: 60000 }, async ({ ffmpeg }) => {
+test("load() again keeps the loaded core", { timeout: 60000 }, async ({ ffmpeg }) => {
   await ffmpeg.writeFile("/kept.txt", "hello");
   expect(await ffmpeg.load({ coreURL: coreURL() })).to.equal(false);
   expect(await ffmpeg.readFile("/kept.txt", "utf8")).to.equal("hello");

tests/ffmpeg/issues/609-wasm-not-wasm.test.js

@@ -5,7 +5,7 @@
 import { expect } from "vitest";
 import { test, coreURL } from "../../helpers/ffmpeg.js";
 
-test.fails("names the URL when the wasm file is not WebAssembly (#609)", async ({ unloaded }) => {
+test("names the URL when the wasm file is not WebAssembly", async ({ unloaded }) => {
   const wasmURL = `${location.origin}/tests/README.md`;
   await expect(unloaded.load({ coreURL: coreURL(), wasmURL })).rejects.toThrow(wasmURL);
 });