[5.x] Fix: Prevent 304 responses without client cache headers #13654
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Fixes statamic#13652 The static caching middleware was unconditionally calling isNotModified() on every cached response, which could incorrectly return HTTP 304 to clients that didn't send cache validation headers (If-None-Match or If-Modified-Since). This caused browsers like Safari to download 0-byte files instead of rendering pages. Root cause: - ApplicationCacher may cache responses with ETag/Last-Modified headers from previous requests - When serving cached responses, these stale headers interfere with fresh ETag generation - isNotModified() evaluates these cached headers and incorrectly returns true even without client validation headers Solution: 1. Clear any stale ETag/Last-Modified headers before setting fresh ETag 2. Only call isNotModified() when request contains cache validation headers (If-None-Match or If-Modified-Since) This preserves ETag functionality for legitimate conditional requests while preventing inappropriate 304 responses. Tested: - Request without cache headers → 200 OK ✓ - Request with If-None-Match → 304 Not Modified ✓
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Fixes #13652
Problem
The static caching middleware was unconditionally calling
isNotModified()on every cached response, which could incorrectly return HTTP 304 to clients that didn't send cache validation headers (If-None-MatchorIf-Modified-Since). This caused browsers like Safari to download 0-byte files instead of rendering pages.Root Cause
ApplicationCachermay cache responses withETag/Last-Modifiedheaders from previous requestsisNotModified()evaluates these cached headers and incorrectly returns true even without client validation headersSolution
This PR updates
src/StaticCaching/Middleware/Cache.phpto:ETag/Last-Modifiedheaders before setting a fresh ETagisNotModified()when the request contains cache validation headers (If-None-MatchorIf-Modified-Since)This preserves ETag functionality for legitimate conditional requests while preventing inappropriate 304 responses.
Testing
If-None-Match→ HTTP 304 Not Modified (ETag functionality preserved)Related
This is related to the ETag support feature introduced in v5.68 (PR #11441), which has had one previous bug fix in v5.70 (#13425).