fix(ci): the invisible-character gate never matched anything - #63
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MEASURED 2026-08-27: this gate's pattern caught 0 OF 6 invisible-character test
cases. It has never detected an NBSP, zero-width space, BOM, soft hyphen, bidi
override or word joiner.
ROOT CAUSE: the pattern used UTF-8 BYTE sequences (\xc2\xa0) while grep -P
matches CHARACTERS. Bytes c2 a0 are ONE character U+00A0; \xc2\xa0 asks for TWO
characters, U+00C2 then U+00A0, which is never present.
grep -P '\xc2\xa0' -> miss
grep -P '\x{a0}' -> MATCH
Only \x00 worked, being single-byte in both readings.
FIXED: codepoint escapes; C0 control characters \x01-\x08,\x0B,\x0C,\x0E-\x1F
added (TAB/LF/CR excluded); and grep -a, without which grep skips any NUL-bearing
file as binary.
The C0 range matters: a stray BACKSPACE byte made a workflow unparseable in
developer-ecosystem, so it never ran, and this linter called it clean.
Canonical fix: hyperpolymath/empty-linter#70. 1 file(s) here.
VERIFIED: YAML re-parsed, and the corrected pattern was confirmed to catch a real
NBSP before the change was kept.
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📝 WalkthroughSummary by CodeRabbit
WalkthroughThe workflow updates its invisible-character pattern to use Unicode code-point escapes. It also makes ChangesInvisible-character scan
Estimated code review effort: 2 (Simple) | ~10 minutes Merge Risk: ⚪ Minimal · up to This localized workflow change corrects invisible-character matching without introducing an actionable merge-blocking risk; it is merge-ready after normal checks. Poem
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 inconclusive)
✅ Passed checks (4 passed)
Full details: Description checkExplanation The description clearly explains the failure, root cause, code changes, and verification. It does not use the repository template headings or include the checklist, but it provides the key required information. Full details: Linked Issues checkExplanation The summary confirms the codepoint escape correction and the use of grep -a. The provided change summary does not confirm the required C0 control range, separate leading-BOM detection, compiled-linter alignment, or the full verification cases from issue Full details: Docstring CoverageExplanation No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.)
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Up to standards ✅🟢 Issues
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Pull Request Overview
This PR successfully fixes the invisible-character linting gate by migrating from UTF-8 byte sequences to Unicode codepoint escapes and expanding the detection range to include C0 control characters. The implementation also ensures that files containing NUL bytes are not skipped.
Codacy analysis indicates the changes are up to standards. However, the implementation of the shell command in the CI workflow is currently inefficient and suppresses errors that could lead to silent failures in environments where the grep engine lacks specific Unicode support.
About this PR
- The PR lacks automated regression tests. Adding a 'test-case' file containing intentional invisible characters to the repository would ensure the gate remains functional and prevent future regressions.
Test suggestions
- Verify detection of Non-Breaking Space (U+00A0)
- Verify detection of Zero-Width Space (U+200B)
- Verify detection of C0 control character (e.g., Backspace \x08)
- Verify grep processes files with NUL bytes (\x00) rather than skipping them as binary
Prompt proposal for missing tests
Consider implementing these tests if applicable:
1. Verify detection of Non-Breaking Space (U+00A0)
2. Verify detection of Zero-Width Space (U+200B)
3. Verify detection of C0 control character (e.g., Backspace \x08)
4. Verify grep processes files with NUL bytes (\x00) rather than skipping them as binary
TIP Improve review quality by adding custom instructions
TIP How was this review? Give us feedback
| -o -name '*.idr' -o -name '*.zig' -o -name '*.v' -o -name '*.jl' \ | ||
| -o -name '*.gleam' -o -name '*.hs' -o -name '*.ml' -o -name '*.sh' \) \ | ||
| -exec grep -Prl "$PATTERNS" {} \; > /tmp/empty-lint-results.txt 2>/dev/null | ||
| -exec grep -aPrl "$PATTERNS" {} \; > /tmp/empty-lint-results.txt 2>/dev/null |
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🟡 MEDIUM RISK
Suggestion: The -r flag is redundant when using find to pass individual file paths. Additionally, using -exec ... + is more efficient as it reduces the total number of processes spawned. Removing the error redirection ensures that any issues with the PCRE engine or the new escape sequences are visible in the logs, rather than resulting in a silent false positive.
| -exec grep -aPrl "$PATTERNS" {} \; > /tmp/empty-lint-results.txt 2>/dev/null | |
| -exec grep -aPl "$PATTERNS" {} + > /tmp/empty-lint-results.txt |
Measured 2026-08-27: this gate caught 0 of 6 invisible-character test cases. It has never detected an NBSP, zero-width space, BOM, soft hyphen, bidi override or word joiner.
Root cause
The pattern used UTF-8 byte sequences (
\xc2\xa0) whilegrep -Pmatches characters. Bytesc2 a0are one character U+00A0;\xc2\xa0asks for two, U+00C2 then U+00A0 — never present.Only
\x00worked, being single-byte in both readings. The gate ran, passed, and could not see what it exists to see.Fixed
\x01-\x08,\x0B,\x0C,\x0E-\x1Fadded (TAB/LF/CR excluded)grep -a— without it grep skips any NUL-bearing file as binaryThe C0 range matters: a stray backspace byte made a workflow unparseable in
developer-ecosystem, so it never ran — and this linter called it clean.Canonical fix: hyperpolymath/empty-linter#70. 1 file(s) here.
Verified: YAML re-parsed, and the corrected pattern was confirmed to catch a real NBSP before the change was kept.