Leaky timeout in Deno with wasm.js and esbuild.build

[hansottowirtz]

Running deno test --allow-all --trace-ops index.ts on this file results in the following error:

running 1 test from ./index.ts
esbuild ... FAILED (208ms)

 ERRORS 

esbuild => ./index.ts:41:6
error: Leaking async ops:
  - 1 async operation to sleep for a duration was started in this test, but never completed. This is often caused by not cancelling a `setTimeout` or `setInterval` call. The operation was started here:
    at handleOpCallTracing (ext:core/01_core.js:561:42)
    at op_sleep (ext:core/01_core.js:378:21)
    at runAfterTimeout (ext:deno_web/02_timers.js:229:20)
    at initializeTimer (ext:deno_web/02_timers.js:187:3)
    at setTimeout (ext:deno_web/02_timers.js:331:10)
    at runtime.scheduleTimeoutEvent (https://deno.land/x/esbuild@v0.19.9/wasm.js:1794:3686)
    at <anonymous> (https://deno.land/x/esbuild@v0.19.9/esbuild.wasm:1:940909)
    at <anonymous> (https://deno.land/x/esbuild@v0.19.9/esbuild.wasm:1:110194)
    at <anonymous> (https://deno.land/x/esbuild@v0.19.9/esbuild.wasm:1:605886)
    at <anonymous> (https://deno.land/x/esbuild@v0.19.9/esbuild.wasm:1:619713)

 FAILURES 

esbuild => ./index.ts:41:6

FAILED | 0 passed | 1 failed (216ms)

error: Test failed

File:

import * as esbuild from "https://deno.land/x/esbuild@v0.19.9/wasm.js";

await esbuild.initialize({
  wasmURL: "https://deno.land/x/esbuild@v0.19.9/esbuild.wasm",
  worker: false,
});

async function bundle(script: string) {
  const esbuildResult = await esbuild.build({
    entryPoints: ['entrypoint.js'],
    sourcemap: 'external',
    target: 'es2022',
    format: 'esm',
    write: false,
    outdir: 'out',
    bundle: true,
    plugins: [
      {
        name: 'simple',
        setup(build) {
          build.onResolve({ filter: /^entrypoint\.js$/ }, () => {
            return {
              path: "/entrypoint.js",
              namespace: 'file',
            }
          })
          build.onLoad({ filter: /^\/entrypoint\.js$/ }, () => {
            return {
              contents: script,
              loader: 'js',
            }
          })
        }
      }
    ]
  });
  esbuild.stop();
  return esbuildResult.outputFiles[0].text;
}

Deno.test("esbuild", async () => {
  await bundle(`
    function add(a, b) {
      return a + b;
    }
    console.log(add(1, 2));
  `);
});

We're running this file in Deno Deploy, which is why we have to use the wasm version with worker: false.

[evanw]

The Go runtime is doing this. You could try asking them about it here: https://github.com/golang/go. Although I’m guessing this is normal. The Go language is garbage collected and the garbage collector has its own timers and scheduling logic that is designed for long-running tasks. Another option could be to look into how to disable this false-positive warning in Deno. I don’t use Deno myself so I don’t know how to do that. Anyway this does not appear to be a problem with esbuild.

[evanw]

Actually, I think I can hack esbuild's WASM runner to clear these timeouts from Go. I'll give that a try.