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EasyRepository SystemsPython 3

Repository Ignore Filter

Filter repository paths with simple ordered ignore and re-include rules.

30m3 sample tests8 hidden tests

Implement filter_repo_paths(paths, rules), a small ordered path filter inspired by repository ignore files. A later exception can restore one manifest while the rest of a generated directory stays excluded.

This exercise defines its own exact/prefix language. It doesn't reproduce .gitignore or .cursorignore syntax, and it isn't a filesystem authorization boundary.

Requirements

  • Preserve the original order of kept paths.
  • Preserve duplicate candidate paths when they are kept. Inputs are lists of strings.
  • Match path and rule text case-sensitively; don't strip or normalize candidate paths.
  • Raise ValueError for invalid paths with empty segments, . segments, or .. traversal.
  • Strip leading and trailing whitespace from each rule before . After strip, blank rules and rules starting with # are ignored.
  • A rule ending in / is a directory prefix match: after stripping the trailing /, path p matches when p.startswith(dir + "/"). The bare directory path equal to dir (for example path dist under rule dist/) does not match; only paths strictly under that prefix do.
  • Otherwise (after optional !), the pattern is an exact full-path match (path == pattern), even if the pattern contains / (e.g. dist/manifest.json).
  • A rule starting with ! re-includes paths matched by earlier rules (exact file or directory prefix, same match rules as non-negated forms).
  • Later matching rules win.
  • Each non-blank, non-comment rule body (after stripping a leading ! and a trailing /) must also be a valid path; raise ValueError when the rule pattern is invalid (empty segments, ., or ..).

Example

Directory prefixes remove descendants. A later exact exception restores only the named file:

ignore-filter-examples.py
1paths = ["src/app.py", "node_modules/lib.js", "dist/app.js"] 2rules = ["node_modules/", "dist/"] 3assert filter_repo_paths(paths, rules) == ["src/app.py"] 4 5# Exact full-path rules may contain `/`; later rules win (including reincludes). 6paths = ["dist/app.js", "dist/manifest.json"] 7rules = ["dist/", "!dist/manifest.json"] 8assert filter_repo_paths(paths, rules) == ["dist/manifest.json"]

The slash matters. Under dist/, dist/app.js matches, but dist and distance/app.js don't. No glob expansion occurs: *.log matches only a candidate literally named *.log.

Track one Boolean per candidate. Start with ignored = False, update it for each matching rule, and append the original candidate only after the last rule. For dist/manifest.json, the rules dist/, !dist/manifest.json, dist/manifest.json produce ignored states True, False, True, so the file is excluded again.

Constraints

  • No glob engine is required.
  • Keep matching deterministic and easy to explain.
  • Validate every non-comment rule even when paths is empty. Validate every candidate even when an earlier rule would exclude it.

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