Code Sentinel
Fix recurring anti-patterns detected by automated code pattern tests.
You MUST use this skill when code pattern tests fail. Even if the fix looks obvious. The anti-pattern files document WHY patterns fail, not just HOW to fix them.
Workflow
- •Run your project's code pattern tests (e.g.,
pytest tests/test_code_patterns.py -v) - •For each failing test, read the anti-pattern file (see index below)
- •Understand the root cause (not just the fix)
- •Apply the documented fix
- •Verify tests pass
Anti-Pattern Index
CI/Workflow Anti-Patterns
Issues that occur in GitHub Actions workflows and CI pipelines.
| Anti-Pattern | File | Automated Test |
|---|---|---|
Heredocs fail inside YAML run: blocks | ci-workflow/yaml-heredoc-indentation.md | test_no_heredocs_in_github_actions |
grep -c || echo "0" creates duplicate output | ci-workflow/grep-exit-code-echo-fallback.md | test_no_grep_exit_code_echo_pattern |
| Git pull/rebase fails with dirty working tree | ci-workflow/git-pull-without-autostash.md | test_git_operations_with_staging |
gh workflow run silently fails without permission | ci-workflow/gh-workflow-run-permissions.md | test_workflow_dispatch_has_actions_permission |
| Windows venv path used on Linux runner | ci-workflow/windows-venv-path-on-linux.md | test_venv_activation_uses_linux_path |
Build/Packaging Anti-Patterns
Issues with PyInstaller bundling, version generation, and cross-platform builds.
| Anti-Pattern | File | Automated Test |
|---|---|---|
| Missing hidden imports after refactoring | build-packaging/pyinstaller-missing-hidden-imports.md | test_pyinstaller_hidden_imports |
| Import path case mismatch breaks bundling | build-packaging/import-path-case-mismatch.md | (manual) |
| Bare imports for sibling modules fail in bundle | build-packaging/sibling-absolute-import-bundling.md | test_sibling_imports_use_relative_syntax |
| Gitignored file committed before rule | build-packaging/gitignored-file-still-tracked.md | (manual) |
| Version hash embedded before commit | build-packaging/version-hash-before-commit.md | (design issue) |
| Windows backslash paths in .spec file | build-packaging/windows-backslash-in-spec.md | test_spec_uses_forward_slashes |
Application/Runtime Anti-Patterns
Issues in application code that cause runtime failures or unexpected behavior.
| Anti-Pattern | File | Automated Test |
|---|---|---|
| Sort without secondary tiebreaker key | application-runtime/sort-without-tiebreaker.md | test_deterministic_file_sorting |
| Fixed window geometry cuts off content | application-runtime/fixed-window-geometry.md | test_no_fixed_window_geometry |
| Same constant defined in multiple modules | application-runtime/duplicate-module-level-constants.md | (manual) |
| Optional import fails silently | application-runtime/silent-optional-import-failure.md | (manual) |
| PIL ImageGrab black on secondary monitor | application-runtime/pil-imagegrab-multimonitor.md | (hardware-dependent) |
| PIL-saved ICO renders invisible | application-runtime/pil-ico-save-invisible.md | (Windows-dependent) |
Quick Reference: Test-to-File Mapping
code
test_no_heredocs_in_github_actions → ci-workflow/yaml-heredoc-indentation.md test_no_grep_exit_code_echo_pattern → ci-workflow/grep-exit-code-echo-fallback.md test_git_operations_with_staging → ci-workflow/git-pull-without-autostash.md test_workflow_dispatch_has_actions_permission → ci-workflow/gh-workflow-run-permissions.md test_venv_activation_uses_linux_path → ci-workflow/windows-venv-path-on-linux.md test_pyinstaller_hidden_imports → build-packaging/pyinstaller-missing-hidden-imports.md test_sibling_imports_use_relative_syntax → build-packaging/sibling-absolute-import-bundling.md test_spec_uses_forward_slashes → build-packaging/windows-backslash-in-spec.md test_deterministic_file_sorting → application-runtime/sort-without-tiebreaker.md test_no_fixed_window_geometry → application-runtime/fixed-window-geometry.md
Common Mistakes
| Mistake | Why It's Wrong |
|---|---|
| "Fix is obvious, skip the skill" | You miss the root cause. Next time you'll make the same mistake. |
| Fixing without reading anti-pattern doc | The doc explains WHY, not just WHAT. Understanding prevents recurrence. |
| Not verifying tests pass | The pattern might exist elsewhere in codebase. |
Adding New Anti-Patterns
When you discover a new recurring issue:
- •Identify the category: CI/Workflow, Build/Packaging, or Application/Runtime
- •Create the file in the appropriate subfolder with a descriptive name
- •Follow the template:
- •Category
- •Issue (one-line summary)
- •Pattern to Avoid (code example)
- •Correct Approach (code example)
- •Why It Fails (root cause explanation)
- •Detection (how to find instances)
- •Test Reference (if automated test exists)
- •Related Commits (historical context)
- •Update this index with the new anti-pattern
- •Add automated test to your project's code pattern test file if feasible
Anti-pattern files: .claude/skills/code-sentinel/anti-patterns/