feat(serve-static): respond 304 for If-Modified-Since requests - #396
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feat(serve-static): respond 304 for If-Modified-Since requests#396SynthLuvr wants to merge 3 commits into
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serveStatic already sets the Last-Modified header, but never honored a client's If-Modified-Since conditional request. Respond with 304 Not Modified when the file has not been modified since the request date. Per RFC 9110, If-Modified-Since is only evaluated for GET/HEAD, is ignored when If-None-Match is present, and invalid dates are ignored. Dates are compared at second granularity since HTTP dates carry no sub-second precision. The 304 is emitted before any response body branch runs, so no read stream is opened and no Content-Length, Content-Range, or Accept-Ranges headers are set; the check also runs after precompressed variant resolution so the served variant's mtime is used. onFound still fires for 304 responses. Fixes honojs#189
Extract the second-granularity date comparison into an isNotModifiedSince predicate so the handler reads as a single guard clause, and de-duplicate the statSync boilerplate in the If-Modified-Since tests.
A 304 response cannot carry representation metadata, so Content-Type and Content-Encoding are no longer sent alongside it, while Last-Modified and Vary are kept to guide cache updates (RFC 9110 Section 15.4.5). Also covers If-Modified-Since being ignored for methods other than GET/HEAD and for field values with more than one member.
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Fixes #189
serveStaticnow evaluatesIf-Modified-Sinceper RFC 9110.Last-Modifiedis already set on every response, so this adds only the conditional check:GET/HEADrequests onlyIf-None-Matchis present, as the latter takes precedenceLast-Modified->If-Modified-Sinceround trip match exactly304 Not Modifiedwith an empty body when the file has not changed since the given dateThe check runs after a file (or a precompressed variant, whose own
mtimeis used) has been found and before the response body is built, so a304skipsContent-Length,Accept-Ranges, andContent-Rangewhile still callingonFound. The comparison lives in a smallisNotModifiedSincepredicate so the handler reads as a single guard clause.A
304keepsLast-ModifiedandVarybut dropsContent-TypeandContent-Encoding, since a304cannot carry representation metadata (Section 15.4.5).Varyis retained so caches still know which precompressed representation was selected. This mirrorsremoveContentHeaderFields()insend, used by Express'serve-static.11 tests cover a
304on an exact and on a later date,200on an earlier date, an invalid header,If-None-Matchprecedence, a non-GET/HEADmethod, a field value with more than one member,HEAD, range requests, precompressed variants, andonFound. All offormat,lint,typecheck,test, andbuild+publintpass locally.The author should do the following, if applicable
pnpm run format:fix && pnpm run lint:fixto format the code