Again ensure comtypes calls raise CallCancelled when cancelled by watchdog - #10279
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…s.WINFUNCTYPE has been replaced with a cancellable version.
… much for what scons needs, and fails as it tries to import core. Rather, just do the specific comtypes.client._generate monkeypatch in comInterfaces_sconscript where it is actually needed.
LeonarddeR
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Sep 26, 2019
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I'm very sorry for reintroducing this regression.
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Link to issue number:
Fixes #10276
Summary of the issue:
In pr #9795 code was added to ensure that CallCancel was raised rather than COMError when a comtypes call was cancelled by watchdog in Python3. In Python2 we did this by overriding
__call__on _ctypes.COMError, however in Python3 this is read-only and can't be done. Therefore in pr #9795 we monkeypatched ctypes.WINFUNCTYPE to return a class with a custom__call__that converted COMError to CallCancelled if it was a cancelled call. We monkeypatched this just before comtypes was imported for the first time and then removed it once the import was done, there by ensuring that comtypes got our custom WINFUNCTYPE.However, in pr #10235, a comtypes.client module was imported at the top of comtypesMonekyPatches.py which forced comtypes to be imported before the WINFUNCTYPE monkeypatching could occur, therefore, comtypes calls no longer would raise CallCancelled when cancelled via watchdog.
Description of how this pull request fixes the issue:
In comtypesMonkeyPatches.py: Moved the import of comtypes.client._generate down to where it is actually needed, below the monkeypatching of WINFUNCTYPE and the initial import of comtypes.
Extra comments have been also added above and below where it is unsafe to import any comtypes modules.
This change did however break builds on appveyor because when comInterfaces_sonscript tried to generate interfaces, our monkeypatched WINFUNCTYPE kicked into action, due to comtypesMonkeyPatches being imported by sconsctruct, and then in some COMErrors further exceptions were raised because core.CallCancelled could not be imported.
Therefore, rather than importing comtypesMonkeypatches in sonstruct, we now just manually do the comtypes.client._generate monkeypatch in comInterfaces_sconscript, specifically where it is needed.
Testing performed:
Performed testcase from issue #10276 and CallCancelled is again correctly raised.
Known issues with pull request:
None.
Change log entry:
None.