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Merged
merged 20 commits into from
Nov 20, 2024
Merged

gh-126615: Make COMError public and add to ctypes doc. #126686

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e70aa54
add `COMError` exception to `Doc/library/ctypes.rst`.
junkmd Nov 16, 2024
181f512
Add a mention of the difference in exceptions that can be raised.
junkmd Nov 16, 2024
857fef5
Add a dot to refer to the object within the same module.
junkmd Nov 16, 2024
90fb47f
Simplify descriptions of attributes.
junkmd Nov 16, 2024
1f9d4ee
Align with the docstring defined in the C implementation:
junkmd Nov 16, 2024
b71e310
Apply suggestions from code review
junkmd Nov 16, 2024
dafb5b2
Add the dot to make the reflink.
junkmd Nov 16, 2024
49d5e5f
Add the `availability`.
junkmd Nov 16, 2024
1fa159a
Create the "Exceptions" section.
junkmd Nov 16, 2024
934c36a
Remove the `availability` directive
junkmd Nov 16, 2024
9461642
`WindowsError` -> `OSError`
junkmd Nov 18, 2024
705ffcc
details of `details`.
junkmd Nov 18, 2024
b5a2170
Small fix.
junkmd Nov 18, 2024
a16f1e2
Make `COMError` public.
junkmd Nov 19, 2024
e2617f3
Update docs.
junkmd Nov 19, 2024
57d76c5
Update `test_COMError`.
junkmd Nov 19, 2024
36f1607
Update the NEWS.
junkmd Nov 20, 2024
068ea2a
`.. versionchanged::` -> `.. versionadded::`
junkmd Nov 20, 2024
3da9e15
Update the `prototype` section.
junkmd Nov 20, 2024
920bccc
Merge branch 'main' into gh_126615_comerror_doc
junkmd Nov 20, 2024
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39 changes: 33 additions & 6 deletions Doc/library/ctypes.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1707,12 +1707,6 @@ in :mod:`!ctypes`) which inherits from the private :class:`_CFuncPtr` class:
and raise an exception if the foreign function call failed.


.. exception:: ArgumentError

This exception is raised when a foreign function call cannot convert one of the
passed arguments.


.. audit-event:: ctypes.set_exception code foreign-functions

On Windows, when a foreign function call raises a system exception (for
Expand Down Expand Up @@ -1799,10 +1793,14 @@ different ways, depending on the type and number of the parameters in the call:
integer. *name* is name of the COM method. *iid* is an optional pointer to
the interface identifier which is used in extended error reporting.

If *iid* is not specified, a :exc:`WindowsError` is raised if the COM method
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WindowsError is now an alias of OSError.

Suggested change
If *iid* is not specified, a :exc:`WindowsError` is raised if the COM method
If *iid* is not specified, an :exc:`OSError` is raised if the COM method

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Good catch.

Thank you.

call fails. If *iid* is specified, a :exc:`.COMError` is raised instead.
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I think (but I'm not 100% sure) that .COMError means Sphinx will search all namespaces, not just ctypes, for a COMError. So it would be better to use ctypes.COMError explicitly:

Suggested change
call fails. If *iid* is specified, a :exc:`.COMError` is raised instead.
call fails. If *iid* is specified, a :exc:`~ctypes.COMError` is raised instead.


COM methods use a special calling convention: They require a pointer to
the COM interface as first argument, in addition to those parameters that
are specified in the :attr:`!argtypes` tuple.


The optional *paramflags* parameter creates foreign function wrappers with much
more functionality than the features described above.

Expand Down Expand Up @@ -2741,3 +2739,32 @@ Arrays and pointers

Returns the object to which to pointer points. Assigning to this
attribute changes the pointer to point to the assigned object.


.. _ctypes-exceptions:

Exceptions
^^^^^^^^^^

.. exception:: ArgumentError

This exception is raised when a foreign function call cannot convert one of the
passed arguments.


.. exception:: COMError(hresult, text, details)

Windows only: This non-public exception is raised when a COM method call
failed.

.. attribute:: hresult

The integer value representing the error code.

.. attribute:: text

The error message.

.. attribute:: details

The 5-tuple representing additional details about the error.
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That's not very helpful. Could you document what the items are?

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@junkmd junkmd Nov 18, 2024 •
edited
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Based on the C implementation source code, these items are retrieved via methods of IErrorInfo1: GetDescription, GetSource, GetHelpFile, GetHelpContext, and the ProgID obtained via using ProgIDFromCLSID and GetGUID.

However, this exception can be raised not only from foreign functions but also intentionally by passing variable-length tuples, as seen in test_win32.py and the comtypes package.

cpython/Lib/test/test_ctypes/test_win32.py

Lines 67 to 76 in f9c5573

def test_COMError(self):
from _ctypes import COMError
if support.HAVE_DOCSTRINGS:
self.assertEqual(COMError.__doc__,
"Raised when a COM method call failed.")
ex = COMError(-1, "text", ("details",))
self.assertEqual(ex.hresult, -1)
self.assertEqual(ex.text, "text")
self.assertEqual(ex.details, ("details",))

I will revise this part, taking these facts into account.

Footnotes

  1. Reference: IErrorInfo implementation in comtypes. ↩

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Since _ctypes is internal API that is subject to change, I think it would be best to change test_win32 and comtypes so that they raise the same 5-tuple as ctypes itself, and document that 5-tuple.

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I wrote details of details.

I plan to improve test_win32 after improving this documentation.

For comtypes, I will investigate how much COMError.details is being used and then discuss the matter with the project's community to decide how to proceed.

As mentioned earlier, I would like to focus on improving the documentation in this PR.

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