Fix: is_fully_escaped does not handle consecutive backslashes correctly#14393
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EternalRights wants to merge 4 commits intopytest-dev:mainfrom
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Fix: is_fully_escaped does not handle consecutive backslashes correctly#14393EternalRights wants to merge 4 commits intopytest-dev:mainfrom
EternalRights wants to merge 4 commits intopytest-dev:mainfrom
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The function only checked if the character immediately before a regex metacharacter was a backslash, but did not count how many consecutive backslashes preceded it. When two backslashes appear before a metacharacter (e.g. r'\\.'), the first escapes the second, leaving the metacharacter unescaped. The function incorrectly reported such strings as fully escaped. Fix by counting consecutive backslashes: an even count means the metacharacter is not escaped, an odd count means it is. Closes pytest-dev#14392
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4 backslashes + pipe: even count means pipe is not escaped, so is_fully_escaped should return False, not True.
alokshukla631
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Apr 20, 2026
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This looks good to me. Counting the run of preceding backslashes matches regex escaping rules much better than the old single-character check, and the added cases make the intended behavior easy to follow.
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Closes #14392
Description
The
is_fully_escapedfunction inraises.pyonly checked whether the character immediately before a regex metacharacter was a backslash. It did not count how many consecutive backslashes preceded the metacharacter.In regex, backslashes escape each other in pairs. So
\\.(two backslashes then a dot) means an escaped backslash followed by an unescaped dot. Butis_fully_escaped(r\\.)was incorrectly returningTruebecause it only checked ifs[i-1]was\.This affects
pytest.raises(match=...)error messages: when the match pattern contains escaped backslashes before a metacharacter, the function incorrectly considers the pattern fully escaped and skips showing a regex diff on match failure.Fix: Count consecutive backslashes before each metacharacter. Even count means the metacharacter is not escaped; odd count means it is.
Type of Change
Checklist