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@Rob--W Rob--W commented Apr 27, 2025

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Overview

There have been issues where the reported error is "ERROR: null", which is very unhelpful. Here is an analysis of a specific example: #5048 (comment)

Although the trigger for that error was fixed by #5074, the unhelpfulness of "ERROR: null" was not addressed.

To help with debugging, this patch prints the original error when this stage is unexpectedly reached.

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  • ✅ login: Rob--W / name: Rob Wu (9f1fad1)

@JoshuaKGoldberg
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Switching to draft pending #5078 (comment). We can't review without a reproduction, and it might be that all buggy behavior was already fixed?

Thanks for the PR in the interim though!

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Rob--W commented May 1, 2025

Switching to draft pending #5078 (comment). We can't review without a reproduction, and it might be that all buggy behavior was already fixed?

For clarity, this is not about fixing whatever that triggered the error, but about improving the logged diagnostics information when an error (unexpectedly) happens.

While the specific trigger was fixed, it is still possible to end up in this case if some other internal error occurs. If you want to reproduce locally, you could throw an error from

console.error('\n Exception during run:', err);

There are probably other ways to trigger this issue, but I haven't looked.

If you are concerned about logging too much information (when an error message is already present), I could add a check to only log the error when the message is null.

@voxpelli voxpelli requested a review from Copilot June 12, 2025 07:45
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Pull Request Overview

This PR enhances error reporting in the CLI by printing the original error object to stderr when an internal error occurs, making the “ERROR: null” message more informative.

  • Prints the caught error object after showing help and the generic error message.
  • Exits with status code 1 after logging the full error.
Comments suppressed due to low confidence (1)

lib/cli/cli.js:64

  • Add a test case that simulates an internal CLI error to verify that the original error message (or stack) is printed as expected.
console.error(err);

lib/cli/cli.js Outdated
debug('caught error sometime before command handler: %O', err);
yargs.showHelp();
console.error(`\n${symbols.error} ${pc.red('ERROR:')} ${msg}`);
console.error(err);

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@Rob--W #5078 is open and I see that you were right all along 🙂. I think this PR is ready for un-drafting - and pretty close to ready for merge. WDYT about the suggested change? And, mind if we un-draft this?

Normally I'd request test coverage but for an edge case like this that "shouldn't" ever happen, I think it's reasonable to skip testing.

lib/cli/cli.js Outdated
Comment on lines 63 to 64
console.error(`\n${symbols.error} ${pc.red('ERROR:')} ${msg}`);
console.error(err);
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[Bug] Most of the, the msg is actually enough on its own. So I don't think we'd want to log the full err - that'd be a lot of extra unnecessary output.

How about only logging err if msg is falsy? Treating it as a kind of targeted backup?

Suggested change
console.error(`\n${symbols.error} ${pc.red('ERROR:')} ${msg}`);
console.error(err);
console.error(`\n${symbols.error} ${pc.red('ERROR:')} ${msg || err}`);

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[Bug] Most of the, the msg is actually enough on its own. So I don't think we'd want to log the full err - that'd be a lot of extra unnecessary output.

Not logging the error when msg is set sounds reasonable to me. I called that out as an option before, at #5344 (comment)

How about only logging err if msg is falsy? Treating it as a kind of targeted backup?

Suggested change
console.error(`\n${symbols.error} ${pc.red('ERROR:')} ${msg}`);
console.error(err);
console.error(`\n${symbols.error} ${pc.red('ERROR:')} ${msg || err}`);

The above could work but would hide the fact that this is an internal error, and also loses the stack trace (which is valuable for debugging). I was thinking of the following:

Suggested change
console.error(`\n${symbols.error} ${pc.red('ERROR:')} ${msg}`);
console.error(err);
console.error(`\n${symbols.error} ${pc.red('ERROR:')} ${msg}`);
if (!msg) {
console.error(err);
}

I did intentionally not stringify the error (or even assume that it is an Error instance). We are in very bad territory, and dumping the raw value (an Error preferably, but could be any promise rejection or thrown value in theory) allows the reader to debug the issue.

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Yeah that makes sense. I'm in favor :)

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@Lightning00Blade Lightning00Blade Dec 19, 2025

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+1 to the having stack trace, as that made it possible to debug #5562 much simpler.

@JoshuaKGoldberg JoshuaKGoldberg added the status: waiting for author waiting on response from OP or other posters - more information needed label Dec 19, 2025
@mark-wiemer mark-wiemer marked this pull request as ready for review December 19, 2025 08:04
@mark-wiemer mark-wiemer marked this pull request as draft December 19, 2025 08:05
@mark-wiemer mark-wiemer self-assigned this Dec 20, 2025
There have been issues where the reported error is "ERROR: null", which
is very unhelpful. Here is an analysis of a specific example:
mochajs#5048 (comment)

Although the trigger for that error was fixed by mochajs#5074, the
unhelpfulness of "ERROR: null" was not addressed.

To help with debugging, this patch prints the original error when this
stage is unexpectedly reached.
@Rob--W Rob--W force-pushed the print-helpful-error-in-worst-case branch from 7cda07e to 9f1fad1 Compare December 30, 2025 00:38
@Rob--W Rob--W marked this pull request as ready for review December 30, 2025 00:39
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codecov bot commented Dec 30, 2025

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 93.50%. Comparing base (9cc3ada) to head (9f1fad1).
⚠️ Report is 1 commits behind head on main.

Files with missing lines Patch % Lines
lib/cli/cli.js 50.00% 1 Missing ⚠️
Additional details and impacted files
@@            Coverage Diff             @@
##             main    #5344      +/-   ##
==========================================
- Coverage   93.52%   93.50%   -0.02%     
==========================================
  Files          57       57              
  Lines        4465     4467       +2     
  Branches      918      919       +1     
==========================================
+ Hits         4176     4177       +1     
- Misses        289      290       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

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  • ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
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@mark-wiemer mark-wiemer added status: needs review a maintainer should (re-)review this pull request and removed status: waiting for author waiting on response from OP or other posters - more information needed labels Dec 31, 2025
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Hey @Rob--W, could you add a new unit test for this? Something that would've failed on main but passes with your changes?

@mark-wiemer mark-wiemer added status: waiting for author waiting on response from OP or other posters - more information needed and removed status: needs review a maintainer should (re-)review this pull request labels Dec 31, 2025
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🐛 Bug: Mocha prints out command help text and ERROR: null when unexpected error in -r module occurs

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