fix(ci): the invisible-character gate never matched anything - #157
fix(ci): the invisible-character gate never matched anything#157hyperpolymath wants to merge 1 commit into
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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 invisible-character detection. The pattern now matches Unicode code points and selected control characters. The ChangesInvisible-character gate
Estimated code review effort: 1 (Trivial) | ~5 minutes Merge Risk: ⚪ Minimal · up to This is a localized CI pattern correction, and no actionable merge-blocking risk remains after normal checks and review. Suggested reviewers: Poem
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Linked Issues checkExplanation The pull request updates the codepoint pattern, adds C0 controls, and uses grep -a. However, 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
The PR fixes the invisible-character gate which was previously ineffective due to incorrect escape sequences. However, a major technical gap remains: when using PCRE (grep -P) for Unicode codepoints, the engine must be explicitly set to UTF-8 mode using the (*UTF) prefix. Without this, the linter will continue to miss multi-byte characters like the Non-Breaking Space (U+00A0) in UTF-8 encoded files.
While Codacy reports that the changes are up to standards, the implementation lacks automated regression tests. Without a sample file containing forbidden characters to verify the linter's output, it is difficult to ensure the gate remains functional after future CI environment updates. Finally, the search logic can be optimized to reduce overhead in the CI pipeline.
About this PR
- To prevent future regressions, consider adding a small automated test or a 'known-fail' sample file to the repository. This would allow the CI to verify that the invisible-character linter is actually capable of detecting the targeted characters in the current environment.
Test suggestions
- Missing recommended test scenario: Verify detection of Non-Breaking Space (U+00A0)
- Missing recommended test scenario: Verify detection of Byte Order Mark (U+FEFF)
- Missing recommended test scenario: Verify detection of C0 control characters like Backspace (\x08)
- Missing recommended test scenario: Verify scanning of files containing NUL bytes using the -a flag
Prompt proposal for missing tests
Consider implementing these tests if applicable:
1. Missing recommended test scenario: Verify detection of Non-Breaking Space (U+00A0)
2. Missing recommended test scenario: Verify detection of Byte Order Mark (U+FEFF)
3. Missing recommended test scenario: Verify detection of C0 control characters like Backspace (\x08)
4. Missing recommended test scenario: Verify scanning of files containing NUL bytes using the -a flag
TIP Improve review quality by adding custom instructions
TIP How was this review? Give us feedback
| # non-breaking spaces, null bytes, and other invisible Unicode in source files. | ||
| set +e | ||
| PATTERNS='\xc2\xa0|\xe2\x80\x8b|\xe2\x80\x8c|\xe2\x80\x8d|\xef\xbb\xbf|\xc2\xad|\xe2\x80\x8e|\xe2\x80\x8f|\xe2\x80\xaa|\xe2\x80\xab|\xe2\x80\xac|\xe2\x80\xad|\xe2\x80\xae|\x00' | ||
| PATTERNS='\x00|[\x01-\x08\x0B\x0C\x0E-\x1F]|\x{a0}|\x{ad}|\x{200b}|\x{200c}|\x{200d}|\x{200e}|\x{200f}|\x{202a}|\x{202b}|\x{202c}|\x{202d}|\x{202e}|\x{2060}|\x{feff}' |
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🔴 HIGH RISK
Enable UTF-8 mode in the PCRE engine to ensure Unicode code points are correctly matched against UTF-8 encoded files.
| PATTERNS='\x00|[\x01-\x08\x0B\x0C\x0E-\x1F]|\x{a0}|\x{ad}|\x{200b}|\x{200c}|\x{200d}|\x{200e}|\x{200f}|\x{202a}|\x{202b}|\x{202c}|\x{202d}|\x{202e}|\x{2060}|\x{feff}' | |
| PATTERNS='(*UTF)\x00|[\x01-\x08\x0B\x0C\x0E-\x1F]|\x{a0}|\x{ad}|\x{200b}|\x{200c}|\x{200d}|\x{200e}|\x{200f}|\x{202a}|\x{202b}|\x{202c}|\x{202d}|\x{202e}|\x{2060}|\x{feff}' |
| -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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⚪ LOW RISK
Suggestion: Optimize the search by passing multiple files to grep at once and removing the redundant recursive flag.
| -exec grep -aPrl "$PATTERNS" {} \; > /tmp/empty-lint-results.txt 2>/dev/null | |
| -exec grep -aPl "$PATTERNS" {} + > /tmp/empty-lint-results.txt 2>/dev/null |
1 participant
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.