mirror of
https://github.com/PrefectHQ/fastmcp.git
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82 lines
2.8 KiB
Python
82 lines
2.8 KiB
Python
"""Tests for FastMCP's exception-to-wire-error translation."""
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from __future__ import annotations
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import pytest
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from mcp import MCPError
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from mcp_types import INTERNAL_ERROR, INVALID_PARAMS
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from fastmcp import Client, FastMCP
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from fastmcp.exceptions import (
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DisabledError,
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NotFoundError,
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PromptError,
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ResourceError,
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ToolError,
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ValidationError,
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to_mcp_error,
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)
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class TestToMcpError:
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@pytest.mark.parametrize(
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"exc",
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[NotFoundError("missing"), DisabledError("off"), ValidationError("bad")],
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)
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def test_invalid_params_mapping(self, exc: Exception):
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"""Not-found, disabled, and validation errors map to INVALID_PARAMS.
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SEP-2164 defines a request naming a nonexistent (or disabled) component
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as an invalid-params error, matching the SDK's own mcpserver mapping.
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"""
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result = to_mcp_error(exc)
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assert isinstance(result, MCPError)
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assert result.error.code == INVALID_PARAMS
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assert result.error.message == str(exc)
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@pytest.mark.parametrize(
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"exc",
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[ResourceError("boom"), PromptError("boom"), ToolError("boom")],
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)
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def test_default_code_for_unmapped_errors(self, exc: Exception):
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"""Operation errors without a dedicated mapping use the default code."""
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assert to_mcp_error(exc).error.code == INTERNAL_ERROR
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def test_custom_default_code(self):
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assert (
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to_mcp_error(ResourceError("x"), default_code=-32000).error.code == -32000
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)
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def test_existing_mcp_error_passes_through(self):
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"""An MCPError chosen upstream survives translation unchanged."""
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existing = MCPError(code=-32000, message="explicit")
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assert to_mcp_error(existing) is existing
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class TestWireErrorCodes:
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"""The core request-handler adapters must emit spec-correct wire codes."""
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async def test_resource_not_found_uses_invalid_params(self):
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"""Resource-not-found is INVALID_PARAMS (-32602), not -32002.
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SEP-2164 corrected this: the SDK's mcpserver maps ResourceNotFoundError
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to INVALID_PARAMS. FastMCP previously deviated with -32002.
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"""
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mcp = FastMCP("test-server")
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async with Client(mcp) as client:
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with pytest.raises(MCPError) as exc_info:
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await client.read_resource_mcp("config://missing")
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assert exc_info.value.error.code == INVALID_PARAMS
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assert "Resource not found" in exc_info.value.error.message
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async def test_prompt_not_found_uses_invalid_params(self):
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mcp = FastMCP("test-server")
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async with Client(mcp) as client:
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with pytest.raises(MCPError) as exc_info:
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await client.get_prompt("missing", {})
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assert exc_info.value.error.code == INVALID_PARAMS
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assert "Unknown prompt" in exc_info.value.error.message
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