Prevent Error.captureStackTrace from erasing Error stack

[bvaughn]

I'm working on some custom Jest matchers for the React repo and I noticed a quirk that I believe is intentional, but doesn't seem optimal. Essentially the problem is this: I'm unable to throw an error from within a custom matcher without the stack being overridden by Jest via Error.captureStackTrace.

So a meaningful stack like this:

ReferenceError: asdf is not defined

  38 |   const foo = () => bar();
  39 |   const bar = () => baz();
> 40 |   const baz = () => asdf();
  41 |   expect(() => {
  42 |     foo();
  43 |   }).toWarnDev([

  at baz (path/to/test.js:40:28)
  at bar (path/to/test.js:39:35)
  at foo (path/to/test.js:38:35)
  at path/to/test.js:42:7
  at Object.matcher (path/to/matcher.js:47:11)
  at Object.<anonymous> (path/to/test.js:43:8)

Becomes a generic stack like this:

ReferenceError: asdf is not defined

  41 |   expect(() => {
  42 |     foo();
> 43 |   }).toWarnDev([
  44 |     'foo',
  45 |     'bar',
  46 |   ]);

  at Object.<anonymous> (path/to/matcher.js:43:8)

I'd like a way to preserve the original stack since it contains useful information. I don't object to the current default behavior, but it would be nice if there was a way to mark a specific error to be skipped. Looking at the source code though, it seems like there aren't really any good options:

• A custom matcher can't throw an instance of JestAssertionError (since the class isn't exposed externally).
• I could set the error.name to "PrettyFormatPluginError" but this is a pretty major hack for a few reasons (it relies on undocumented internals and it would modify the error message logged to the developer).
• I could override Error.captureStackTrace, but this could not be done within the matcher; rather it would need to be done in a global beforeEach hook.

What would you think of an approach like the one React uses for error logging (eg a special property Jest checks for on an error like dangerousDontCaptureStack that prevents the stack from being overridden)?

[bvaughn]

What would you think of an approach like the one React uses for error logging (eg a special property Jest checks for on an error like dangerousDontCaptureStack that prevents the stack from being overridden)?

I would be happy to submit a PR that adds this functionality if there are no objections. 😄

[SimenB]

We really should export JestAssertionError, would that be enough?

Sorta related, if you know how to keep a stack across frames, help with #5104 would be appreciated :D

[bvaughn]

Yeah, that would be even nicer. It just seemed (potentially) more controversial. I'd be happy to put together a PR for that instead.

[github-actions]

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