[Feature]: Support `Error.prototype.cause`

[silverwind]

🚀 Feature Proposal

Some new APIs like fetch make use of Error.prototype.cause which jest does not display at all for thrown errors, which makes debugging these errors harder than necessary.

Motivation

It will make errors with cause easier to debug.

Example

test("cause", () => {
  try {
    throw new Error("cause");
  } catch (err) {
    throw new Error("wrapped", {cause: err});
  }
});

Will output only the wrapped error message, which is often unhelpful:

 FAIL  ./test.js
  ● cause

    wrapped

It'd be better if the cause message would also be shown:

 FAIL  ./test.js
  ● cause

    wrapped
    cause

Pitch

Because Error.prototype.cause is a standard Javascript feature.

[SimenB]

We should definitely add this, yeah! I added support to our logger at work just a few weeks ago 😀

PR welcome, most changes should be in https://github.com/facebook/jest/blob/d1626e9395263b0c7c207777c0ca570b2147aaa8/packages/jest-message-util/src/index.ts

[silverwind]

As errors in error.cause can contain more errors with causes attached, I guess a recursion limit will be necessary to prevent circular references and such. I guess a limit of 10 should work for most cases.

[SimenB]

And like node, duplicate traces should be removed.

$ node -p "new Error('asdasd', {cause: new Error('cause')})"
Error: asdasd
    at [eval]:1:1
    at Script.runInThisContext (node:vm:129:12)
    ... 4 lines matching cause stack trace ...
    at node:internal/main/eval_string:27:3 {
  [cause]: Error: cause
      at [eval]:1:29
      at Script.runInThisContext (node:vm:129:12)
      at Object.runInThisContext (node:vm:313:38)
      at node:internal/process/execution:76:19
      at [eval]-wrapper:6:22
      at evalScript (node:internal/process/execution:75:60)
      at node:internal/main/eval_string:27:3
}

(note 4 lines matching cause stack trace )

---

Not necessary for an initial implementation, of course

[davecardwell]

util.inspect() on an Error will produce a string with the cause in the expected format:

$ node -e "console.log(util.inspect(new Error('asdasd', {cause: new Error('cause')})))"
Error: asdasd
    at [eval]:1:26
    at Script.runInThisContext (node:vm:129:12)
    ... 4 lines matching cause stack trace ...
    at node:internal/main/eval_string:27:3 {
  [cause]: Error: cause
      at [eval]:1:54
      at Script.runInThisContext (node:vm:129:12)
      at Object.runInThisContext (node:vm:305:38)
      at node:internal/process/execution:76:19
      at [eval]-wrapper:6:22
      at evalScript (node:internal/process/execution:75:60)
      at node:internal/main/eval_string:27:3
}

[silverwind]

Related change there is https://github.com/nodejs/node/pull/41002.

[kkyusufk]

I can take this up if no one has started work @SimenB

[SimenB]

Go for it! 🙂

[kkyusufk]

Hey apologies, I am starting work on this today. I got caught in some other work.

[SimenB]

Duplicate of #12053.

PR is of course still very much welcome!

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