Use removeprefix to strip weak ETag indicator in is_not_modified#3193
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Kludex merged 3 commits intoJun 10, 2026
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strip(" W/") removes individual characters from the set {' ', 'W', '/'}
from both ends of the string, which can mangle ETag values that happen
to end with those characters. Use strip() + removeprefix("W/") instead
to only strip whitespace and then remove the literal W/ prefix.
Signed-off-by: gnosyslambda <[email protected]>
themavik
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Mar 23, 2026
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Good catch on strip(" W/") — it can remove unrelated characters at the ends of a strong etag. strip() plus removeprefix("W/") matches the weak-etag prefix case without over-stripping the quoted value.
themavik
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tag.strip().removeprefix("W/") fixes weak ETag handling compared to strip(" W/"), which could eat unrelated leading characters.
naarob
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Mar 26, 2026
…D route precedence (Kludex#3182) fix Kludex#3193: staticfiles.is_not_modified() used tag.strip(' W/') which operates on a character set, incorrectly trimming ETags ending in 'W' or '/'. Replaced with a normalize_etag() helper that uses str.startswith('W/') for prefix removal. fix Kludex#3182: Route.__init__ adds HEAD implicitly when GET is defined, causing the GET route to steal HEAD requests before any explicit HEAD route can match. Tracked _explicit_methods and return Match.PARTIAL for implicit HEAD so explicit HEAD routes registered at the same path can take precedence.
removeprefix to strip weak ETag indicator in is_not_modified
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is_not_modified()usestag.strip(" W/")to remove the weak ETag prefix, butstrip()works on a character set — it strips any combination of' ','W', and'/'from both ends of the string. This means an ETag value ending inWor/would get incorrectly trimmed.Replaced with
tag.strip().removeprefix("W/")which strips whitespace first, then removes the literalW/prefix only.removeprefixis available since Python 3.9 and Starlette requires 3.10+.In practice this is unlikely to cause issues with the current MD5-based ETags from FileResponse, but the fix makes the code do what it actually intends to do.