Log unhandled promise rejections in the rageshake

[uhoreg]

Fixes element-hq/element-web#26639

Checklist

• Tests written for new code (and old code if feasible)
• Linter and other CI checks pass
• Sign-off given on the changes (see CONTRIBUTING.md)

---

This change is marked as an internal change (Task), so will not be included in the changelog.

[uhoreg]

Not sure what's the best way to test this. Is there a way to check if something got logged?

[t3chguy]

Is there a way to check if something got logged?

You could call IndexedDBLogStore::consume and see whether the line you expect made it?

[uhoreg]

It looks like Jest installs its own handler for unhandled rejections, which interferes with the handler that I've installed. I tried writing a test as:

import { init } from "../src/rageshake/rageshake";
import { sleep } from "matrix-js-sdk/src/utils";

describe("rageshake", () => {
    it("should log unhandled promise rejections", async () => {
        await init(false);

        new Promise((resolve, reject) => { reject("foo"); });

        await sleep(2000); // wait for the promise to reject

        const logs = global.mx_rage_logger.flush();

        expect(logs).toMatch(/Unhandled promise rejection: foo/);
    });
});

And get the following output from Jest:

yarn run jest test/Rageshake-test.ts
yarn run v1.22.19
$ /home/hubert/Projects/element/matrix-react-sdk/node_modules/.bin/jest test/Rageshake-test.ts
 FAIL  test/Rageshake-test.ts
  rageshake
    ✕ should log unhandled promise rejections (2006 ms)

  ● rageshake › should log unhandled promise rejections

    thrown: "foo"

      at _getError (node_modules/jest-circus/build/utils.js:432:18)
          at Array.map (<anonymous>)

  ● rageshake › should log unhandled promise rejections

    expect(received).toMatch(expected)

    Expected pattern: /Unhandled promise rejection: foo/
    Received string:  ""

      28 |         const logs = global.mx_rage_logger.flush();
      29 |
    > 30 |         expect(logs).toMatch(/Unhandled promise rejection: foo/);
         |                      ^
      31 |     });
      32 | });
      33 |

      at Object.<anonymous> (test/Rageshake-test.ts:30:22)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 total
Snapshots:   0 total
Time:        3.897 s, estimated 4 s
Ran all test suites matching /test\/Rageshake-test.ts/i.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

So you can see that Jest handles the rejection.

Any suggestions for how to get around this?

I did try in Element Web, and it does log unhandled promise rejections:

[t3chguy]

Any suggestions for how to get around this?

Expect the throw

...
await expect(() => new Promise((resolve, reject) => reject("foo"))).rejects.toThrowError();
const logs = global.mx_rage_logger.flush();
...

(or similar; untested)

Though I guess this may also handle it which means your handler won't fire either. urgh

[uhoreg]

Since Jest doesn't want to let me test the code, and none of the other rageshake code has tests either, does anyone mind if I bypass the testing quality gate?

[richvdh]

🚢