🚀 Feature: Support printing each error within AggregateErrors

[domenic]

Is your feature request related to a problem or a nice-to-have?? Please describe.

Sometimes I'm using Mocha to test something which can fail multiple ways. This is what AggregateError is designed for.

However, when an AggregateError is thrown in a Mocha test, nothing nice prints:

it("should work with AggregateErrors", () => {
  const err1 = new Error("1");
  const err2 = new Error("2");
  const aggErr = new AggregateError([err1, err2], "2 errors");

  throw aggErr;
});

gives

  1) should work with AggregateErrors:
     AggregateError: 2 errors
      at Context.<anonymous> (x.test.js:4:18)
      at process.processImmediate (node:internal/timers:478:21)

Describe the solution you'd like

It should probably print something for each error, as well as the AggregateError itself. Maybe

     AggregateError: 2 errors
      at Context.<anonymous> (x.test.js:4:18)
      at process.processImmediate (node:internal/timers:478:21)

      Error: 1
        at Context.<anonymous> (x.test.js:2:16)
        at process.processImmediate (node:internal/timers:478:21)

      Error: 2
        at Context.<anonymous> (x.test.js:3:16)
        at process.processImmediate (node:internal/timers:478:21)

Describe alternatives you've considered

I tried making a fake AggregateError:

it("should work with fake AggregateErrors", () => {
  const err1 = new Error("1");

  const err2 = new Error("2");

  const aggErr = new Error(`2 errors:\n\n${err1.stack}\n\n${err2.stack}`);

  throw aggErr;
});

This seems to confuse Mocha's stack trace defection code and result in printing the error twice:

  1) should work with fake AggregateErrors:
     2 errors:

Error: 1
    at Context.<anonymous> (C:\Users\Domenic\Dropbox\Programming\WIP\jest-aggregateerror-test\x.test.js:2:16)
    at callFn (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runnable.js:366:21)
    at Runnable.run (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runnable.js:354:5)
    at Runner.runTest (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:666:10)
    at C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:789:12
    at next (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:581:14)
    at C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:591:7
    at next (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:474:14)
    at Immediate._onImmediate (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:559:5)
    at process.processImmediate (node:internal/timers:478:21)

Error: 2
    at Context.<anonymous> (C:\Users\Domenic\Dropbox\Programming\WIP\jest-aggregateerror-test\x.test.js:4:16)
    at callFn (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runnable.js:366:21)
    at Runnable.run (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runnable.js:354:5)
    at Runner.runTest (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:666:10)
    at C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:789:12
    at next (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:581:14)
    at C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:591:7
    at next (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:474:14)
    at Immediate._onImmediate (C:\Users\Domenic\AppData\Local\npm-cache\_npx\508606763866ae01\node_modules\mocha\lib\runner.js:559:5)
    at process.processImmediate (node:internal/timers:478:21)
  Error: 2 errors:

  Error: 1
      at Context.<anonymous> (x.test.js:2:16)
      at process.processImmediate (node:internal/timers:478:21)

  Error: 2
      at Context.<anonymous> (x.test.js:4:16)
      at process.processImmediate (node:internal/timers:478:21)
      at Context.<anonymous> (x.test.js:6:18)
      at process.processImmediate (node:internal/timers:478:21)

This is my current best solution but it's pretty noisy to get duplicate errors.

[voxpelli]

Agree on the need for this 👍

Similar to the need for a better support for Error Causes: #4829