Preserve component metadata in response cache (#4521)

tests/server/middleware/test_caching.py

@@ -42,6 +42,7 @@ from fastmcp.server.middleware.caching import (
 )
 from fastmcp.server.middleware.middleware import CallNext, MiddlewareContext
 from fastmcp.tools.base import Tool, ToolResult
+from fastmcp.utilities.tasks import TaskConfig
 
 TEST_URI = AnyUrl("https://test_uri")
 
@@ -352,6 +353,47 @@ class TestResponseCachingMiddlewareIntegration:
 
             assert pre_tool_list == post_tool_list
 
+    async def test_list_operations_preserve_component_metadata(self):
+        """Base component fields should survive conversion through the cache."""
+        icon = mcp_types.Icon(src="https://example.com/component.png")
+        mcp = FastMCP("MetadataServer")
+        mcp.add_middleware(ResponseCachingMiddleware())
+
+        @mcp.tool(icons=[icon], task=TaskConfig(mode="optional"))
+        async def greet() -> str:
+            return "hello"
+
+        @mcp.resource("resource://metadata", icons=[icon])
+        def metadata_resource() -> str:
+            return "resource"
+
+        @mcp.prompt(icons=[icon])
+        def metadata_prompt() -> str:
+            return "prompt"
+
+        cached_tools = await mcp.list_tools()
+        cached_resources = await mcp.list_resources()
+        cached_prompts = await mcp.list_prompts()
+        assert type(cached_tools[0]) is Tool
+        assert type(cached_resources[0]) is Resource
+        assert type(cached_prompts[0]) is Prompt
+        assert not hasattr(cached_tools[0], "fn")
+        assert not hasattr(cached_resources[0], "fn")
+        assert not hasattr(cached_prompts[0], "fn")
+
+        async with Client(mcp) as client:
+            for _ in range(2):
+                tools = await client.list_tools()
+                resources = await client.list_resources()
+                prompts = await client.list_prompts()
+
+                assert tools[0].icons == [icon]
+                assert tools[0].execution == mcp_types.ToolExecution(
+                    task_support="optional"
+                )
+                assert resources[0].icons == [icon]
+                assert prompts[0].icons == [icon]
+
     async def test_call_tool(
         self,
         caching_server: FastMCP,
@@ -595,13 +637,16 @@ class TestCachingWithImportedServerPrefixes:
     ):
         """Resource URIs should retain prefix after being served from cache."""
         async with Client(parent_with_imported_child) as client:
-            # First call populates cache
-            resources_first = await client.list_resources()
-            resource_uris_first = [str(r.uri) for r in resources_first]
+            with warnings.catch_warnings():
+                warnings.simplefilter("error", UserWarning)
 
-            # Second call should come from cache
-            resources_cached = await client.list_resources()
-            resource_uris_cached = [str(r.uri) for r in resources_cached]
+                # First call populates cache
+                resources_first = await client.list_resources()
+                resource_uris_first = [str(r.uri) for r in resources_first]
+
+                # Second call should come from cache
+                resources_cached = await client.list_resources()
+                resource_uris_cached = [str(r.uri) for r in resources_cached]
 
             # All resources should have prefix in URI path in both calls
             # Resources get path-style prefix: resource://child/path