fix(backends): warn on every Memcached clear_path() call - #342
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Memcached cannot enumerate keys, so clear_path() only deletes a key named exactly as the path and never matches an HTTP cache key (method|||host|||path|||query). Only include_params=True warned, so the default call returned 0 silently and a response stayed cached after a write. Warn on every call and point to invalidate(request), which rebuilds the route's exact key; document that in BACKENDS.md and HTTP_CACHING.md. Closes #320
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Problem
MemcachedBackend.clear_path(path)deletes only a key named exactlypath. HTTP cache keys aremethod|||host|||path|||query, so it never removes a cached response. Onlyinclude_params=Truewarned; the default call returned0silently, so the "clear the path after a write" pattern kept serving stale data on Memcached (#320).Change
clear_path()on Memcached emits aRuntimeWarningon every call, pointing toinvalidate(request), which rebuilds the route's exact key and works on every backend. Behaviour is otherwise unchanged (the literal key is still deleted).examples/http_cache.pynotes it next to itsclear_path()call.changelog.d/320.fixed.md.Callers running with warnings as errors will now see the warning on the default call; that is the point of the change.
Tests
test_memcached_clear_path_always_warns[False|True](stubbed client, checks the warning points at the caller).test_memcached_invalidate_drops_what_clear_path_cannot: the report's scenario on a live Memcached.clear_path()warns and leaves the stale response;invalidate()removes it.clear_pathtests now expect the warning.Without the source change, 8 tests in
tests/backends/test_memcached.pyfail. Full suite, ruff, mypy strict and pre-commit pass.Closes #320