Jean-Pierre MartineauandClaude Fable 5.1
c9f5a71ce7
Apache-2.0 does not require per-file headers, but a file lifted out of the tree carried no marking at all. One comment line, first (or right after a shebang), on every .py under meshterm/, tests/, packaging/ and scripts/, plus the extensionless SPI bridge; tests/test_spdx.py keeps a new file from landing without one. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
83 lines
3.2 KiB
Python
83 lines
3.2 KiB
Python
# SPDX-License-Identifier: Apache-2.0
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"""Tests for the private Windows DLL handles.
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These pin a crash that only ever appeared in a frozen build on Windows, which is the
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worst place for a bug to live: no traceback survived, because the window it was printed
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in was destroyed by the same exit that printed it.
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``ctypes.windll.kernel32`` is a cache shared by the whole process. MeshTerm's emoji-width
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probe declared ``GetConsoleScreenBufferInfo`` as taking a pointer to its own copy of the
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screen-buffer struct; prompt_toolkit then called that same function object with a pointer
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to *its* copy — same layout, different class — and ctypes refused the call while the app
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was building its screen.
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"""
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from __future__ import annotations
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import ctypes
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import sys
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import pytest
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from meshterm.core import win32dll
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pytestmark = pytest.mark.skipif(sys.platform != "win32", reason="Windows libraries")
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def test_each_handle_is_its_own() -> None:
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"""Two callers get two objects, so neither can see the other's declarations."""
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assert win32dll.kernel32() is not win32dll.kernel32()
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assert win32dll.user32() is not win32dll.user32()
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def test_the_shared_windll_is_the_thing_being_avoided() -> None:
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"""The premise: ``ctypes.windll`` hands the same function object to every caller.
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If this ever stops being true the module is unnecessary — but until then it is the
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reason it exists, so it is worth asserting rather than assuming.
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"""
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first = ctypes.windll.kernel32.GetConsoleScreenBufferInfo
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second = ctypes.windll.kernel32.GetConsoleScreenBufferInfo
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assert first is second
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def test_declaring_a_signature_does_not_reach_the_shared_one() -> None:
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"""The regression itself: our declarations must not be visible to anyone else.
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Before this module existed, the assignment below rewrote the signature that
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prompt_toolkit's console output later called through, and the application died on
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startup with ``expected LP__CSBI instance instead of pointer to
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CONSOLE_SCREEN_BUFFER_INFO``.
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"""
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class _MineAlone(ctypes.Structure):
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_fields_ = [("whatever", ctypes.c_int)]
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shared = ctypes.windll.kernel32.GetConsoleScreenBufferInfo
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before = shared.argtypes
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private = win32dll.kernel32()
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private.GetConsoleScreenBufferInfo.argtypes = [
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ctypes.c_void_p,
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ctypes.POINTER(_MineAlone),
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]
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assert ctypes.windll.kernel32.GetConsoleScreenBufferInfo.argtypes == before
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assert private.GetConsoleScreenBufferInfo is not shared
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def test_the_probe_leaves_the_shared_signature_alone() -> None:
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"""End to end: running the emoji probe must not disturb the process-wide function.
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The narrow assertion above can pass while the real call site still reaches for
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``ctypes.windll``, so this exercises the code that actually crashed.
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"""
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from meshterm.ui.tui import emoji_width
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shared = ctypes.windll.kernel32.GetConsoleScreenBufferInfo
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before = shared.argtypes
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# No console under pytest, so this returns None rather than measuring. That is fine:
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# the declarations happen before the first call either way, which is what matters.
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emoji_width._win_probe_width("x") # noqa: SLF001 - the point is this private path
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assert ctypes.windll.kernel32.GetConsoleScreenBufferInfo.argtypes == before
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