fix: detect upper-accented+currency mojibake at string start (fixes #222)#232
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fix: detect upper-accented+currency mojibake at string start (fixes #222)#232gaoflow wants to merge 1 commit into
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When an upper-accented letter (such as Ã) is followed by a currency
symbol (such as ¥, YEN SIGN) at the very beginning of a string, the
badness heuristic failed to detect it as mojibake. An existing pattern
(`\s [{upper_accented}] [{currency}]`) already caught this case when
a preceding whitespace was present, but the start-of-string case was
missing.
Add a BADNESS_RE pattern `^[{upper_accented}][{currency}]\w` that
matches this sequence at position 0 only when followed by a word
character. The trailing `\w` ensures the pattern does not match the
isolated 2-character substring that `decode_inconsistent_utf8` passes
to `is_bad()` during processing of other text, preventing false
positives on ambiguous embedded sequences like "Dråber".
Fixes rspeer#222.
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The badness heuristic in
is_bad()misses UTF-8 mojibake when an upper-accented letter followed by a currency symbol appears at the very beginning of a string. An existing pattern (\s [{upper_accented}] [{currency}]) already catches this when preceded by whitespace, but the start-of-string case was missing.For example,
fix_encoding("Ã¥klagarmyndighets")returns"Ã¥klagarmyndighets"unchanged instead of correctly decoding to"åklagarmyndighets".Root cause: No BADNESS_RE pattern matches
[{upper_accented}][{currency}]at position 0 without a preceding space or lowercase letter.Fix: Add
^[{upper_accented}][{currency}]\wto detect this sequence at string start. The trailing\wis required so the pattern does not match the isolated 2-character substring thatdecode_inconsistent_utf8passes tois_bad(), preventing false positives on ambiguous embedded sequences (like the"Dråber"negative test case from issue #202).Changes:
ftfy/badness.py: Add new BADNESS_RE alternation (4 lines)tests/test-cases/synthetic.json: Add test case for the reported bug