34 lines
1.6 KiB
Python
34 lines
1.6 KiB
Python
"""Invariants for ``tools/mcp_tool_errors._format_connect_error`` on malformed exception chains.
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``__cause__``/``__context__`` can form a cycle (the same OAuth error re-raised on the SSE fallback,
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a raised-and-caught pair) and stdio failures can nest deeper than the recursion limit; either used
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to turn ``hermes mcp test`` into a RecursionError that hid the real connect error (#111952, #111997).
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"""
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import sys
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from tools.mcp_tool_errors import _format_connect_error
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def test_format_connect_error_reports_real_messages_on_cyclic_chain():
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"""A two-node ``__cause__``/``__context__`` cycle renders every distinct message, once, in chain order."""
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first = RuntimeError("first failure")
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second = RuntimeError("second failure")
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first.__cause__ = second
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second.__context__ = first
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assert _format_connect_error(first) == "first failure; second failure"
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def test_format_connect_error_finds_missing_executable_through_deep_cyclic_chain():
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"""A missing stdio binary wrapped deeper than the recursion limit, with the chain looping back to the top,
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is still reported as the missing executable rather than as a RecursionError."""
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missing = FileNotFoundError(2, "No such file or directory", "/opt/homebrew/bin/removed-mcp-server")
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current = missing
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for _ in range(sys.getrecursionlimit() + 10):
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wrapper = RuntimeError("stdio startup failed")
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wrapper.__cause__ = current
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current = wrapper
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missing.__context__ = current
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assert _format_connect_error(current) == "missing executable '/opt/homebrew/bin/removed-mcp-server'"
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