cpp-linter fails to submit a comment

[kduske]

What events trigger your workflow?

name: CPP Linter
on: [pull_request]

What OS does your workflow use?

runs-on: ubuntu-22.04

How is cpp-linter-action configured?

- name: Run clang-tidy
        uses: cpp-linter/cpp-linter-action@v2
        id: linter
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        with:
          version: 18
          style: 'file'  # Use .clang-format config file. 
          tidy-checks: '' # Use .clang-tidy config file.
          files-changed-only: false
          database: ${{github.workspace}}/build
          ignore: 'build|vcpkg-overlay-ports|common/src/ui/GetVersion.cpp'
          step-summary: true
          thread-comments: true
      - name: Fail fast?!
        if: steps.linter.outputs.clang-tidy-checks-failed > 0
        run: exit 1

What was the unexpected behavior?

cpp-linter fails to post a comments when it is done. This just started happening and I'm not aware of changing anything that could have caused this. Here's the relevant log excerpt (full run here):

2025-12-22T15:50:14.9913387Z ##[group]Posting comment(s)
2025-12-22T15:50:14.9927368Z Traceback (most recent call last):
2025-12-22T15:50:14.9937136Z   File "/home/runner/work/_actions/cpp-linter/cpp-linter-action/v2/.venv/bin/cpp-linter", line 10, in <module>
2025-12-22T15:50:14.9938432Z     sys.exit(main())
2025-12-22T15:50:14.9938727Z              ^^^^^^
2025-12-22T15:50:14.9939569Z   File "/home/runner/work/_actions/cpp-linter/cpp-linter-action/v2/.venv/lib/python3.12/site-packages/cpp_linter/__init__.py", line 85, in main
2025-12-22T15:50:14.9940321Z     rest_api_client.post_feedback(files=files, args=args, clang_versions=clang_versions)
2025-12-22T15:50:14.9941138Z   File "/home/runner/work/_actions/cpp-linter/cpp-linter-action/v2/.venv/lib/python3.12/site-packages/cpp_linter/rest_api/github_api.py", line 221, in post_feedback
2025-12-22T15:50:14.9941784Z     comment = super().make_comment(
2025-12-22T15:50:14.9942005Z               ^^^^^^^^^^^^^^^^^^^^^
2025-12-22T15:50:14.9942641Z   File "/home/runner/work/_actions/cpp-linter/cpp-linter-action/v2/.venv/lib/python3.12/site-packages/cpp_linter/rest_api/__init__.py", line 213, in make_comment
2025-12-22T15:50:14.9943302Z     comment += RestApiClient._make_tidy_comment(
2025-12-22T15:50:14.9943562Z                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2025-12-22T15:50:14.9944236Z   File "/home/runner/work/_actions/cpp-linter/cpp-linter-action/v2/.venv/lib/python3.12/site-packages/cpp_linter/rest_api/__init__.py", line 275, in _make_tidy_comment
2025-12-22T15:50:14.9944901Z     diagnostic=note.diagnostic_link,
2025-12-22T15:50:14.9945127Z                ^^^^^^^^^^^^^^^^^^^^
2025-12-22T15:50:14.9945781Z   File "/home/runner/work/_actions/cpp-linter/cpp-linter-action/v2/.venv/lib/python3.12/site-packages/cpp_linter/clang_tools/clang_tidy.py", line 95, in diagnostic_link
2025-12-22T15:50:14.9946529Z     return link + "{}/{}.html)".format(*self.diagnostic.split("-", maxsplit=1))
2025-12-22T15:50:14.9946864Z                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2025-12-22T15:50:14.9947229Z IndexError: Replacement index 1 out of range for positional args tuple
2025-12-22T15:50:15.0290484Z ##[error]Process completed with exit code 1.
2025-12-22T15:50:15.0462777Z Post job cleanup.

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🔗 Similar Issues

Related Issues

• response returned 403 from POST (thread-comments for a PR) #327
• an not dismiss a commented pull request review #290
• Error after recent update (v2.16.0) #313
• lines-changed-only: true -> always analyses +1 line #388
• clang-tidy cannot be disabled since v2.16.1 #323

🔗 Related PRs

cpp-linter/cpp-linter-rs#37 - resort to paginated requests for changed files [merged]
cpp-linter/cpp-linter-rs#53 - add CI to detect performance regressions [merged]
cpp-linter/cpp-linter#124 - feat: capture and output clang version used [merged]
cpp-linter/cpp-linter-rs#77 - fix: clang-tidy diagnostic comments in PR review [merged]
#324 - fix: pass inputs as uninterpretted strings [merged]

👤 Suggested Assignees

• 2bndy5
• quqiOnfree
• amir-bialek
• mccrearyp
• mkmer

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[2bndy5]

@kduske can re-run the job with debug logging enabled? I need to see the clang-tidy output, specifically the clang-tidy diagnostic(s) name (usually a hyphenated tag name like [readability-braces-around-statements]).

The error is from a feature that tries to hyperlink a diagnostic name with clang-tidy docs. For example, readability-braces-around-statements.

[kduske]

@2bndy5 thank you for looking into this. I have restarted the job here: https://github.com/TrenchBroom/TrenchBroom/actions/runs/20434261854/job/58745888493

[2bndy5]

Unfortunately, that didn't didn't enable cpp-linter debug logs (could be a separate problem on our end). Which means, I still don't see any clang-tidy output. (patch proposed in cpp-linter/cpp-linter#174)

I'm also seeing a rogue --extra-arg= (with no value) being passed to clang-tidy. Yet another problem we need to fix on our end (patch proposed in cpp-linter/cpp-linter#172).

I already know how to fix this (IndexError: Replacement index 1 out of range) problem (see patch proposed in cpp-linter/cpp-linter#173), but I was hoping to get insight on what exactly in clang-tidy's stdout was causing it. Knowing what exactly is causing this (in clang-tidy's stdout) would help write a unit test to prevent regressions.

Normally, I would just emulate the workflow locally, but I don't have QT installed (which is a bit of a pain in my past experience).

As a last resort, I think enabling verbose output in cpp-linter explicitly may be required:

- uses: cpp-linter/cpp-linter-action@v2
  with:
    verbosity: debug

This used to be on by default, but it was a bit too much logs for normal runs; many of our users scan a lot of C/C++ files in each run.

[kduske]

Thank you for your reply, I have enabled debug verbosity and retriggered the workflow here: https://github.com/TrenchBroom/TrenchBroom/actions/runs/20434261854

Hope that helps you to find the issue, let me know if there's anything else i can do.

[2bndy5]

Sorry, the logs are the same on that run; no clang-tidy output. I see you made the requested changes on your cleanup-io branch: TrenchBroom/TrenchBroom@33ccb84. But the CI never ran with those changes on that branch. The run you linked was for the correct branch but for the wrong commit (specifically the last commit in the PR TrenchBroom/TrenchBroom#5026).

FWIW, I noticed you have about 18 branches for which a corresponding PR was closed, 1 branch that was merged, and 1 branch pending review in a drafted PR. That is only some of the 56 total branches on your github remote. This must be confusing/difficult to navigate at some point, right?

[kduske]

Sorry, the logs are the same on that run; no clang-tidy output. I see you made the requested changes on your cleanup-io branch: TrenchBroom/TrenchBroom@33ccb84. But the CI never ran with those changes on that branch. The run you linked was for the correct branch but for the wrong commit (specifically the last commit in the PR TrenchBroom/TrenchBroom#5026).

Yeah, I messed that up, but this one should be correct now: https://github.com/TrenchBroom/TrenchBroom/actions/runs/20465335970

Sorry for the confusion.

FWIW, I noticed you have about 18 branches for which a corresponding PR was closed, 1 branch that was merged, and 1 branch pending review in a drafted PR. That is only some of the 56 total branches on your github remote. This must be confusing/difficult to navigate at some point, right?

Yeah, I should clean that up. But I mainly use PRs to trigger actions, so I never run into these issues.

[2bndy5]

Ok, I finally found the problem.

Enclosed is a zip of txt files that isolate points of contention in the logs:
issue389.zip

There is 1 file where clang-tidy crashes (seg fault) and dump the stack trace. But that's not what causes the issue here.

For the diagnostics reported on file common/test/src/mdl/tst_ReadFreeImageTexture.cpp, there's a line that cpp-linter misinterprets as a start of a diagnostic:

/home/runner/work/TrenchBroom/TrenchBroom/common/test/src/mdl/tst_ReadFreeImageTexture.cpp:44:48: note: candidate template ignored: substitution failure [with file:auto = typename std::remove_reference<shared_ptr<File> &>::type]

Note, the line ends with text enclosed in square brackets. Our regex pattern flags this enclosed text as a clang-tidy diagnostic name. This is definitely what is causing cpp-linter to crash when posting the comment.

Unfortunately, this isn't as easy as ignoring the diagnostic name if there is no hyphens. I'm going to have to check the diagnostic name for spaces and hyphens before appending the line as a start of a diagnostic report.

@kduske Thank you so much for getting me this feedback. It proves that my initial gut reaction was insufficient!

[kduske]

Enclosed is a zip of txt files that isolate points of contention in the logs: issue389.zip

There is 1 file where clang-tidy crashes (seg fault) and dump the stack trace. But that's not what causes the issue here.

Thank you for digging that out, that file was a leftover and wasn't even part of the build!

Unfortunately, this isn't as easy as ignoring the diagnostic name if there is no hyphens. I'm going to have to check the diagnostic name for spaces and hyphens before appending the line as a start of a diagnostic report.

@kduske Thank you so much for getting me this feedback. It proves that my initial gut reaction was insufficient!

I'm glad I could help! Thank you for your support and for providing this very useful action!