Use logs instead of warnings

src/fastmcp/resources.py

@@ -4,7 +4,6 @@ import abc
 import asyncio
 import json
 import logging
-import warnings
 from pathlib import Path
 from typing import Dict, Optional, Callable, Any
 from urllib.parse import parse_qs, urlparse
@@ -226,11 +225,7 @@ class ResourceManager:
         existing = self._resources.get(resource.uri)
         if existing:
             if self.warn_on_duplicate_resources:
-                warnings.warn(
-                    f"Resource already exists: {resource.uri}",
-                    ResourceWarning,
-                    stacklevel=2,
-                )
+                logger.warning(f"Resource already exists: {resource.uri}")
             return existing
         self._resources[resource.uri] = resource
         return resource

src/fastmcp/tools.py

@@ -1,7 +1,6 @@
 """Tool management for FastMCP."""
 
 import inspect
-import warnings
 from typing import Any, Callable, Dict, Optional
 
 from pydantic import BaseModel, Field, TypeAdapter
@@ -85,11 +84,7 @@ class ToolManager:
         existing = self._tools.get(tool.name)
         if existing:
             if self.warn_on_duplicate_tools:
-                warnings.warn(
-                    f"Tool already exists: {tool.name}",
-                    ResourceWarning,
-                    stacklevel=2,
-                )
+                logging.warning(f"Tool already exists: {tool.name}")
             return existing
         self._tools[tool.name] = tool
         return tool

tests/test_resource_manager.py

@@ -1,4 +1,4 @@
-import warnings
+import logging
 import pytest
 from pathlib import Path
 from tempfile import NamedTemporaryFile, TemporaryDirectory
@@ -276,8 +276,9 @@ class TestResourceManagerAdd:
                 path=Path("test.txt"),
             )
 
-    def test_warn_on_duplicate_resources(self):
+    def test_warn_on_duplicate_resources(self, caplog):
         """Test warning on duplicate resources."""
+        caplog.set_level(logging.WARNING, logger="mcp")
         manager = ResourceManager()
         resource = FileResource(
             uri="file:///test.txt",
@@ -285,11 +286,12 @@ class TestResourceManagerAdd:
             path=Path("/test.txt"),
         )
         manager.add_resource(resource)
-        with pytest.warns(ResourceWarning):
-            manager.add_resource(resource)
+        manager.add_resource(resource)
+        assert "Resource already exists: file:///test.txt" in caplog.text
 
-    def test_disable_warn_on_duplicate_resources(self):
+    def test_disable_warn_on_duplicate_resources(self, caplog):
         """Test disabling warning on duplicate resources."""
+        caplog.set_level(logging.WARNING, logger="mcp")
         manager = ResourceManager()
         resource = FileResource(
             uri="file:///test.txt",
@@ -298,9 +300,8 @@ class TestResourceManagerAdd:
         )
         manager.add_resource(resource)
         manager.warn_on_duplicate_resources = False
-        with warnings.catch_warnings():
-            warnings.simplefilter("error")
-            manager.add_resource(resource)
+        manager.add_resource(resource)
+        assert "Resource already exists: file:///test.txt" not in caplog.text
 
 
 class TestResourceManagerRead:

tests/test_tool_manager.py

@@ -1,5 +1,4 @@
-import warnings
-
+import logging
 import pytest
 from pydantic import BaseModel
 
@@ -83,7 +82,7 @@ class TestAddTools:
         ):
             manager.add_tool(lambda x: x)
 
-    def test_warn_on_duplicate_tools(self):
+    def test_warn_on_duplicate_tools(self, caplog):
         """Test warning on duplicate tools."""
 
         def f(x: int) -> int:
@@ -91,10 +90,11 @@ class TestAddTools:
 
         manager = ToolManager()
         manager.add_tool(f)
-        with pytest.warns(ResourceWarning):
+        with caplog.at_level(logging.WARNING):
             manager.add_tool(f)
+            assert "Tool already exists: f" in caplog.text
 
-    def test_disable_warn_on_duplicate_tools(self):
+    def test_disable_warn_on_duplicate_tools(self, caplog):
         """Test disabling warning on duplicate tools."""
 
         def f(x: int) -> int:
@@ -103,9 +103,9 @@ class TestAddTools:
         manager = ToolManager()
         manager.add_tool(f)
         manager.warn_on_duplicate_tools = False
-        with warnings.catch_warnings():
-            warnings.simplefilter("error")
+        with caplog.at_level(logging.WARNING):
             manager.add_tool(f)
+            assert "Tool already exists: f" not in caplog.text
 
 
 class TestCallTools: