CODEOWNERS Shadow Checker

Report

Rules

Files with no matching rule

Common questions

What does "last match wins" actually mean?

GitHub checks a file's path against every pattern in CODEOWNERS, in file order, and the LAST pattern that matches decides who owns the file -- not the most specific one, and not the first one. This is the same rule .gitignore uses. A narrow rule near the top of the file is silently overridden the moment a broader rule that also matches gets added anywhere below it, however much later.

Why does a broad rule added later break a specific rule that already worked?

The specific rule still exists and still matches its files -- it just stops winning, because the new broad rule matches those same files and sits after it in the list. Nothing errors, nothing warns, and the pull requests it used to route for review just quietly stop requiring that reviewer. This is the single most common way a CODEOWNERS file drifts from what its author intended.

How is this different from GitHub's own CODEOWNERS syntax highlighting?

GitHub's editor flags syntax errors -- an unknown user, a malformed pattern. It does not check whether a rule ever actually wins ownership of a real file in your repository, because that requires resolving every pattern against every path and comparing winners, which is exactly what this tool does against the file list you provide.

A rule shows as "unmatched" instead of "shadowed" -- what is the difference?

Shadowed means the rule matched files in your list but a later rule always overrode it -- real evidence the rule is dead weight. Unmatched means the rule matched nothing in your list at all, which usually means a typo in the pattern, a path that no longer exists, or simply a sample that did not happen to include a matching file -- so it is reported separately rather than lumped in with genuine shadowing.

Does a clean report mean my CODEOWNERS file is correct?

It means no rule in your file is dead weight against the files you listed, every owner is syntactically valid, and every listed file has a matching rule (or is flagged as uncovered). It cannot tell you an owner is a real collaborator on the repository -- that needs an authenticated GitHub API call this tool deliberately never makes -- and it can only see the files you gave it, so a file you left out of the list is not checked.