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f9b4b8af34
Some exception classes (e.g. anyio.ClosedResourceError) are raised without
a message argument, so str(exc) returns an empty string. The existing error
format f'{type(exc).__name__}: {exc}' would produce messages like
'MCP call failed: ClosedResourceError: ' with nothing after the colon.
Add _exc_str() helper that falls back to repr(exc) when str(exc) is empty,
and apply it to all 6 MCP error formatting sites (5 tool/prompt/resource
handlers + 1 sampling handler).
Fixes #19417
89 lines
2.9 KiB
Python
89 lines
2.9 KiB
Python
"""Regression tests for MCP error messages when str(exc) is empty.
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Issue #19417: ClosedResourceError (and similar exceptions raised without a
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message argument) produced ``MCP call failed: ClosedResourceError: `` with
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nothing after the colon, making debugging impossible.
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Fix: ``_exc_str()`` falls back to ``repr(exc)`` when ``str(exc)`` is empty.
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"""
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import json
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from types import SimpleNamespace
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from unittest.mock import MagicMock, patch
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import pytest
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from tools.mcp_tool import _exc_str, _sanitize_error
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# ---------------------------------------------------------------------------
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# _exc_str unit tests
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# ---------------------------------------------------------------------------
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class _EmptyMessageError(Exception):
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"""Exception whose __str__ returns empty string (like anyio.ClosedResourceError)."""
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def __str__(self):
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return ""
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class _NormalError(Exception):
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pass
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def test_exc_str_returns_str_when_nonempty():
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exc = _NormalError("something broke")
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assert _exc_str(exc) == "something broke"
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def test_exc_str_falls_back_to_repr_when_str_empty():
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exc = _EmptyMessageError()
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result = _exc_str(exc)
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assert result != ""
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assert "_EmptyMessageError" in result
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def test_exc_str_falls_back_to_repr_for_whitespace_only():
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"""str(exc) that is only whitespace should also trigger the repr fallback."""
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exc = Exception(" ")
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result = _exc_str(exc)
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# After strip(), the text is empty, so repr is used
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assert result.strip() != ""
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def test_exc_str_handles_closedresource_like_exception():
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"""Simulate anyio.ClosedResourceError which has no message."""
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# Replicate the real anyio.ClosedResourceError behavior
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exc = type("ClosedResourceError", (Exception,), {"__str__": lambda self: ""})()
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result = _exc_str(exc)
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assert "ClosedResourceError" in result
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assert result != ""
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# ---------------------------------------------------------------------------
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# Integration: error message format in _sanitize_error
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# ---------------------------------------------------------------------------
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def test_error_message_not_empty_when_exc_has_no_message():
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"""The formatted error string should always contain the exception class name."""
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exc = _EmptyMessageError()
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error_msg = _sanitize_error(
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f"MCP call failed: {type(exc).__name__}: {_exc_str(exc)}"
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)
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assert "ClosedResourceError" not in error_msg or "_EmptyMessageError" in error_msg
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# The key invariant: the message must not end with ": "
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assert not error_msg.endswith(": ")
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# And it must contain the exception type name
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assert "_EmptyMessageError" in error_msg
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def test_error_message_preserves_normal_exception_text():
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"""Normal exceptions should still show their message text."""
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exc = _NormalError("connection refused")
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error_msg = _sanitize_error(
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f"MCP call failed: {type(exc).__name__}: {_exc_str(exc)}"
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)
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assert "connection refused" in error_msg
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assert "_NormalError" in error_msg
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