Ignore if-modified-since if if-none-match is present

[Kludex]

• Closes comply with http caching validation with etag and if-modified-since #2891
• Closes staticfile caching breaks if mtimes are not available even though etags differ. #3052
• Closes rfc-conformity for cache validation #3053

I've added both @Smixi-syn and @grindhold as co-authors. Thanks for the help!

[Copilot]

Pull Request Overview

This PR refactors the ETag validation logic in the StaticFiles.is_not_modified method and adds test coverage for the RFC 7232 behavior where if-none-match takes precedence over if-modified-since.

• Simplified the ETag matching logic using a walrus operator and removed unnecessary try-except block
• Added test case verifying that if-none-match header is evaluated independently of if-modified-since

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
starlette/staticfiles.py	Refactored is_not_modified method to use walrus operator and return ETag match result directly
tests/test_staticfiles.py	Added test case for ETag mismatch with timestamp match to verify header precedence behavior

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[grindhold]

awesome! thanks for taking action so quickly :)

[Smixi-syn]

Hi, thanks for the merge :) !
Just a small note, as mentionned, if people overide the FileResponse/StaticFiles and didn't set the etag in the dictionnary, then it will crash when the file is retrieved. I don't know if this can be considered a breaking change ?

[Kludex]

Hi, thanks for the merge :) ! Just a small note, as mentionned, if people overide the FileResponse/StaticFiles and didn't set the etag in the dictionnary, then it will crash when the file is retrieved. I don't know if this can be considered a breaking change ?

It's not. I've added a note there - people would be able to track the problem easily if they do something weird.