fix(mcpserver): return resource not found code

Author: go165

src/mcp/server/mcpserver/server.py

@@ -448,7 +448,7 @@ async def read_resource(
         try:
             resource = await self._resource_manager.get_resource(uri, context)
         except ValueError as exc:
-            raise ResourceError(f"Unknown resource: {uri}") from exc
+            raise MCPError(code=-32002, message=f"Resource not found: {uri}") from exc
 
         try:
             content = await resource.read()

tests/interaction/_requirements.py

@@ -901,12 +901,6 @@ def __post_init__(self) -> None:
     "mcpserver:resource:unknown-uri": Requirement(
         source=f"{SPEC_BASE_URL}/server/resources#error-handling",
         behavior="resources/read for a URI matching no registered resource returns JSON-RPC error -32002.",
-        divergence=Divergence(
-            note=(
-                "The spec reserves -32002 for resource-not-found; MCPServer raises ResourceError, which "
-                "the low-level server converts to error code 0."
-            ),
-        ),
     ),
     # ═══════════════════════════════════════════════════════════════════════════
     # Prompts

tests/interaction/mcpserver/test_resources.py

@@ -114,7 +114,7 @@ def user_profile(user_id: str) -> str:
 async def test_read_unknown_uri_is_error(connect: Connect) -> None:
     """Reading a URI that matches no registered resource fails with a JSON-RPC error.
 
-    The spec reserves -32002 for resource-not-found; see the divergence note on the requirement.
+    The spec reserves -32002 for resource-not-found.
     """
     mcp = MCPServer("library")
 
@@ -127,7 +127,7 @@ def app_config() -> str:
         with pytest.raises(MCPError) as exc_info:
             await client.read_resource("config://missing")
 
-    assert exc_info.value.error == snapshot(ErrorData(code=0, message="Unknown resource: config://missing"))
+    assert exc_info.value.error == snapshot(ErrorData(code=-32002, message="Resource not found: config://missing"))
 
 
 @requirement("mcpserver:resource:read-throws-surfaced")