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https://github.com/PrefectHQ/fastmcp.git
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52100b08ff
Fixes issue #2431 where exclude_args fails when excluded parameters have non-serializable types (e.g., ServerSession). The fix excludes parameters from function annotations before Pydantic tries to serialize them. Also adds deprecation notice that exclude_args will be deprecated in FastMCP 2.14 in favor of dependency injection.
124 lines
3.9 KiB
Python
124 lines
3.9 KiB
Python
from typing import Any
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import pytest
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from mcp.server.session import ServerSession
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from fastmcp import Client, FastMCP
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from fastmcp.tools.tool import Tool
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async def test_tool_exclude_args_in_tool_manager():
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"""Test that tool args are excluded in the tool manager."""
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mcp = FastMCP("Test Server")
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@mcp.tool(exclude_args=["state"])
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def echo(message: str, state: dict[str, Any] | None = None) -> str:
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"""Echo back the message provided."""
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if state:
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# State was read
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pass
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return message
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tools_dict = await mcp._tool_manager.get_tools()
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tools = list(tools_dict.values())
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assert len(tools) == 1
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assert "state" not in tools[0].parameters["properties"]
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async def test_tool_exclude_args_without_default_value_raises_error():
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"""Test that excluding args without default values raises ValueError"""
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mcp = FastMCP("Test Server")
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with pytest.raises(ValueError):
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@mcp.tool(exclude_args=["state"])
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def echo(message: str, state: dict[str, Any] | None) -> str:
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"""Echo back the message provided."""
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if state:
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# State was read
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pass
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return message
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async def test_add_tool_method_exclude_args():
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"""Test that tool exclude_args work with the add_tool method."""
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mcp = FastMCP("Test Server")
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def create_item(
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name: str, value: int, state: dict[str, Any] | None = None
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) -> dict[str, Any]:
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"""Create a new item."""
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if state:
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# State was read
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pass
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return {"name": name, "value": value}
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tool = Tool.from_function(
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create_item,
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name="create_item",
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exclude_args=["state"],
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)
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mcp.add_tool(tool)
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# Check internal tool objects directly
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tools_dict = await mcp._tool_manager.get_tools()
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tools = list(tools_dict.values())
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assert len(tools) == 1
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assert "state" not in tools[0].parameters["properties"]
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async def test_tool_functionality_with_exclude_args():
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"""Test that tool functionality is preserved when using exclude_args."""
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mcp = FastMCP("Test Server")
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def create_item(
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name: str, value: int, state: dict[str, Any] | None = None
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) -> dict[str, Any]:
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"""Create a new item."""
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if state:
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# state was read
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pass
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return {"name": name, "value": value}
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tool = Tool.from_function(
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create_item,
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name="create_item",
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exclude_args=["state"],
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)
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mcp.add_tool(tool)
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# Use the tool to verify functionality is preserved
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async with Client(mcp) as client:
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result = await client.call_tool(
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"create_item", {"name": "test_item", "value": 42}
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)
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assert result.data == {"name": "test_item", "value": 42}
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async def test_exclude_args_with_non_serializable_type():
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"""Test that exclude_args works even when the excluded parameter type can't be serialized.
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This test ensures that exclude_args works correctly when the excluded parameter
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has a type that Pydantic cannot serialize (like ServerSession). The bug was that
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get_cached_typeadapter would try to serialize all parameters before compress_schema
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could exclude them, causing a PydanticSchemaGenerationError.
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"""
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def my_tool(message: str, session: ServerSession | None = None) -> str:
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"""A tool that takes a non-serializable Session parameter."""
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return message
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# This should not raise an error even though ServerSession can't be serialized
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tool = Tool.from_function(
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my_tool,
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name="my_tool",
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exclude_args=["session"],
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)
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# Verify the tool was created successfully
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assert tool is not None
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assert tool.name == "my_tool"
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# Verify the session parameter is excluded from the schema
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assert "session" not in tool.parameters["properties"]
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assert "message" in tool.parameters["properties"]
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