Make CacheConfig() the Client cache default and None the off switch (#3164)

tests/client/test_client_caching.py

@@ -212,11 +212,11 @@ def test_a_custom_store_with_an_explicit_target_id_constructs_for_any_server() -
     assert _coordinator(client)._store is store
 
 
-async def test_cache_false_disables_the_cache_and_the_handler_wrap() -> None:
+async def test_cache_none_disables_the_cache_and_the_handler_wrap() -> None:
     async def handler(message: IncomingMessage) -> None:
         raise NotImplementedError
 
-    client = Client(_list_changed_server(), cache=False, message_handler=handler)
+    client = Client(_list_changed_server(), cache=None, message_handler=handler)
     assert client._response_cache is None
 
     async with client:
@@ -224,7 +224,7 @@ async def test_cache_false_disables_the_cache_and_the_handler_wrap() -> None:
 
 
 def test_the_default_cache_uses_a_per_client_in_memory_store() -> None:
-    """`cache=None` (the default) is cache-on."""
+    """The default `CacheConfig()` is cache-on."""
     server = Server("plain")
     first = Client(server)
     second = Client(server)
@@ -637,7 +637,7 @@ async def test_a_read_resource_carrying_meta_is_fetched_and_replaces_the_warm_en
 async def test_cache_mode_is_inert_when_caching_is_disabled() -> None:
     server, fetches = _varying_tools_server()
 
-    async with Client(server, cache=False) as client:
+    async with Client(server, cache=None) as client:
         await client.list_tools()
         await client.list_tools(cache_mode="use")
         await client.list_tools(cache_mode="refresh")

tests/client/test_subscriptions.py

@@ -595,7 +595,7 @@ async def test_client_listen_installs_the_cache_eviction_barrier_exactly_when_a_
         with anyio.fail_after(5):
             async with cached_client.listen(tools_list_changed=True) as sub:  # pragma: no branch
                 assert sub._on_event == cached_client._evict_for_listen_event  # pyright: ignore[reportPrivateUsage]
-    async with Client(_bus_server(bus), cache=False) as uncached_client:
+    async with Client(_bus_server(bus), cache=None) as uncached_client:
         with anyio.fail_after(5):
             async with uncached_client.listen(tools_list_changed=True) as sub:  # pragma: no branch
                 assert sub._on_event is None  # pyright: ignore[reportPrivateUsage]

tests/docs_src/test_caching.py

@@ -102,9 +102,9 @@ async def test_a_hintless_result_is_not_cached_by_default() -> None:
     assert fetches == [None, None]
 
 
-async def test_cache_false_makes_every_call_a_round_trip() -> None:
+async def test_cache_none_makes_every_call_a_round_trip() -> None:
     server, fetches = _counting_tools_server()
-    async with Client(server, cache=False) as client:
+    async with Client(server, cache=None) as client:
         await client.list_tools()
         await client.list_tools()
     assert fetches == [None, None]