Summary

Stack trace lines were display: inherit which was causing them to be inline which was allowing errors to be concatenated.

So for the code:

      const error = new Error('error');
      const errorWithStringCause = new Error('error with string cause', {
        cause: 'string cause',
      });
      const errorWithErrorCause = new Error('error with error cause', {
        cause: error,
      });

      console.info('1. two regular errors as two args:');
      console.error(error, error);

      console.info('2. an error after an error with string cause:');
      console.error(errorWithStringCause, error);

      console.info('3. an error after an error with error cause:');
      console.error(errorWithErrorCause, error);

We've got the first console print like so:

However it was only happening for when the ignored frames were displayed. Otherwise it was acting as expected:

It was also acting as expected if there was any cause for the error:

Test plan

After the fix, stack frames never have an error printed in the same line (inline):

• Collapsed ignore frames:

• Displayed ignore frames:

• This change maintains backwards compatibility with previous Local Storage data (if modifying settings, experiments, or other persisted client state).

Upstreaming plan

• This commit should be sent as a patch to the upstream devtools-frontend repo following the contribution guide for Meta employees OR contribution guide.
• This commit is React Native-specific and cannot be upstreamed.