feat: add auto-fix option for automatic clang-format fixing by shenxianpeng · Pull Request #443 · cpp-linter/cpp-linter-action

shenxianpeng · 2026-06-08T16:29:54Z

Summary

Closes #439

Adds an auto-fix option that automatically applies clang-format fixes and commits them back to the PR branch, eliminating the manual fix-and-repush cycle.

Changes

`action.yml`

New input auto-fix (default false): When enabled, passes --fix to cpp-linter and runs git auto-commit
New input auto-fix-commit-msg (default style: apply styling format fix): Custom commit message for auto-fix commits
"Run cpp-linter" step: Conditionally appends --fix arg when auto-fix=true
New "Auto-commit clang-format fixes" step: After linter runs:
1. Checks for git changes
2. Commits as github-actions[bot]
3. Pushes to the PR branch
4. Push failures degrade to warnings (not errors)

Docs

README.md: Added auto-fix usage section with example, including [skip ci] tip
docs/action.yml: Added metadata for new inputs (min-version 2.19.0, permissions)
docs/permissions.md: Added auto-fix permissions section (contents: write)
docs/examples/index.md: Added auto-fix recipe
.github/workflows/examples/auto-fix.yml: New example workflow

Dependencies

Requires cpp-linter/cpp-linter#202 (adds --fix CLI flag to cpp-linter).

Design Decisions

Decision	Rationale
Always fix the entire file	clang-format cannot target specific line ranges with `-i`
Use `github-actions[bot]` as author	Standard practice for automated commits
No `[skip ci]` in default message	Users opt-in via custom `auto-fix-commit-msg`
Push failure → warning, not error	Graceful degradation; branch protection may block push
Auto-fix doesn't affect comment/review logic	Format issues are fixed before comments are posted, so no format-related comments appear

2bndy5

Some notes.

I also think that the PR reviews should not have the full patch (from each tool used) in the review's summary comment, especially if this feature is an option.

2bndy5 · 2026-06-09T00:18:40Z

+          ^git config user.name 'github-actions[bot]'
+          ^git config user.email '41898282+github-actions[bot]@users.noreply.github.com'


Better to use the env vars present: GITHUB_ACTOR and GITHUB_ACTOR_ID. This way, the commits will be associated with the user that triggered the event for the workflow's run.

Suggested change

^git config user.name 'github-actions[bot]'

^git config user.email '41898282+github-actions[bot]@users.noreply.github.com'

^git config user.name $"($env.GITHUB_ACTOR)"

^git config user.email $"($env.GITHUB_ACTOR_ID)+($env.GITHUB_ACTOR)@users.noreply.github.com"

Also, this can be done for a single git commit command instead of all git commands in the CI workflow:

let git_user = $"user.name=($env.GITHUB_ACTOR)" let git_email = $"user.email=($env.GITHUB_ACTOR_ID)+($env.GITHUB_ACTOR)@users.noreply.github.com" ^git -c $git_user -c $git_email commit -m $commit_msg

I am not sure if the outside contributor can commit with their own user/email in GitHub actions.
If it's not a problem. It seems good. othersie use a bot user like github-actions[bot] dependabot[bot], pre-commit-ci[bot] are also not bad.

github-actions[bot] would be good enough if the GITHUB_TOKEN env var is never supplied a PAT (personal access token). If using a PAT, then the owner of the PAT will not be the github-actions[bot].

By using the GITHUB_ACTOR(_ID), we can at least point to the committer that caused violations to be auto-fixed with a new commit.

I am not sure if the outside contributor can commit with their own user/email in GitHub actions

I do this all the time with my automated publishing scripts. See the nu script I wrote for publishing packages from cpp-linter-rs

2bndy5 · 2026-06-09T00:19:25Z

+          } else {
+            '${{ inputs.auto-fix-commit-msg }}'
+          }
+          ^git commit -m $"($commit_msg)"


See my previous comment about setting the user name and email of a single git command.

2bndy5 · 2026-06-09T00:24:09Z

+      if: inputs.auto-fix == 'true' || inputs.auto-fix == true
+      shell: nu {0}
+      run: |
+        let has_changes = (^git diff --exit-code) | complete | $in.exit_code != 0


If this returns true, then it is because cpp-linter left some cache artifacts behind. Currently, cpp-linter makes sure the scanned source files are unchanged. Any changes are done in memory or in cache. If changes are done to the C/C++ sources, then they are undone before exiting run_clang_format() or run_clang_tidy().

This feature needs special handling in cpp-linter first; see cpp-linter/cpp-linter#82 for a discussion of the complexity that hasn't been addressed yet.

Oh sorry, I didn't see you submitted cpp-linter/cpp-linter#202

2bndy5 · 2026-06-09T00:37:35Z

          '--jobs=${{ inputs.jobs }}'
        ]
+        if '${{ inputs.auto-fix }}' == 'true' {
+          $args = ($args | append ['--fix'])


The self-test CI fails here because all variables are immutable by default in nushell. To declare them mutable, use mut instead of let (above this line):

- let args = [ + mut args = [

…rmat fixes Adds two new inputs: - auto-fix: runs cpp-linter --fix and auto-commits changes - fix-commit-msg: custom commit message (default: 'style: apply styling format fix') The auto-fix workflow: 1. Runs cpp-linter with --fix (applies clang-format -i) 2. If there are changed files, commits and pushes as github-actions[bot] 3. Push failures degrade to a warning Closes #439

2bndy5 · 2026-06-09T09:30:45Z

+      contents: write # (1)!
+```
+
+1. Needed to commit and push the formatted changes back to the PR branch.


We should also note that this permission is only needed by the token used in actions/checkout (which defaults to github.token).

However, the github.token is NOT able to trigger new CI runs when used to push a commit. If users want the auto-fix commit to trigger a new CI run, then they need to provide it with a PAT that has contents: write permission.

- uses: actions/checkout@v6 with: # MY_TOKEN must have `contents: write` permission. # using default token does not trigger CI runs on `git push` token: ${{ secrets.MY_TOKEN }}

github-actions Bot added bug Something isn't working documentation Improvements or additions to documentation enhancement New feature or request labels Jun 8, 2026

2bndy5 requested changes Jun 9, 2026

View reviewed changes

2bndy5 reviewed Jun 9, 2026

View reviewed changes

2bndy5 removed the bug Something isn't working label Jun 9, 2026

shenxianpeng added 2 commits June 9, 2026 10:20

refactor: rename fix-commit-msg to auto-fix-commit-msg for consistency

ff93734

shenxianpeng force-pushed the feature/auto-fix branch from b4670df to ff93734 Compare June 9, 2026 07:20

github-actions Bot added the bug Something isn't working label Jun 9, 2026

2bndy5 reviewed Jun 9, 2026

View reviewed changes

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

feat: add auto-fix option for automatic clang-format fixing#443

feat: add auto-fix option for automatic clang-format fixing#443
shenxianpeng wants to merge 2 commits into
mainfrom
feature/auto-fix

shenxianpeng commented Jun 8, 2026 •

edited

Loading

Uh oh!

2bndy5 left a comment

Uh oh!

2bndy5 Jun 9, 2026

Uh oh!

shenxianpeng Jun 9, 2026

Uh oh!

2bndy5 Jun 9, 2026

Uh oh!

2bndy5 Jun 9, 2026

Uh oh!

2bndy5 Jun 9, 2026

Uh oh!

2bndy5 Jun 9, 2026

Uh oh!

2bndy5 Jun 9, 2026

Uh oh!

2bndy5 Jun 9, 2026 •

edited

Loading

Uh oh!

2bndy5 Jun 9, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

		^git config user.name 'github-actions[bot]'
		^git config user.email '41898282+github-actions[bot]@users.noreply.github.com'

Conversation

shenxianpeng commented Jun 8, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Changes

action.yml

Docs

Dependencies

Design Decisions

Uh oh!

2bndy5 left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

2bndy5 Jun 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

shenxianpeng commented Jun 8, 2026 •

edited

Loading

`action.yml`

2bndy5 Jun 9, 2026 •

edited

Loading