Link to issue number:

None. Related to #12971 and #12843 comment

Summary of the issue:

Registering for custom UIA annotations and properties can only be done after NVDAHelper is initialized. In normal usage this is not a problem, however since registration occurs on import it is impossible to write unit tests or generate developer documentation for anything which imports from NVDAObjects.UIA. The error when generating developer documentation is as follows:

WARNING: autodoc: failed to import module 'MSHTML' from module 'NVDAObjects.IAccessible'; the following exception was raised:
Traceback (most recent call last):
  File "D:\my_repos\nvda\.venv\lib\site-packages\sphinx\ext\autodoc\importer.py", line 58, in import_module
    return importlib.import_module(modname)
  File "C:\Python37\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "D:\my_repos\nvda\source\NVDAObjects\IAccessible\MSHTML.py", line 29, in <module>
    from NVDAObjects.UIA import UIA, UIATextInfo
  File "D:\my_repos\nvda\source\NVDAObjects\UIA\__init__.py", line 962, in <module>
    class UIA(Window):
  File "D:\my_repos\nvda\source\NVDAObjects\UIA\__init__.py", line 963, in UIA
    _UIACustomProps = UIAHandler.customProps.CustomPropertiesCommon.get()
  File "D:\my_repos\nvda\source\UIAHandler\customProps.py", line 75, in get
    cls._instance = cls()
  File "D:\my_repos\nvda\source\UIAHandler\customProps.py", line 83, in __init__
    uiaType=UIAutomationType.INT,
  File "<string>", line 6, in __init__
  File "D:\my_repos\nvda\source\UIAHandler\customProps.py", line 54, in __post_init__
    self.id = NVDAHelper.localLib.registerUIAProperty(
AttributeError: 'NoneType' object has no attribute 'registerUIAProperty'

Description of user facing changes

This should affect only developers - classes holding custom UIA properties and annotations are no longer singletons.

Description of development approach

Rather than making UIAHandler.customAnnotations.CustomAnnotationTypesCommon, UIAHandler.customProps.CustomPropertiesCommon and the Excel specific annotations and properties singletons, we now register for custom properties and annotations first time they're needed rather than on import. To avoid unnecessary interactions with UIA registered id's are cached for lifetime of NVDA. While at it I've also moved imports below the module level docstring since that is the more standard place.

Testing strategy:

• Compiled developer documentation - made sure that no errors from not initialized NVDAHelper are shown
• Smoke tested custom UIA properties by ensuring that item positions can be reported in Windows Explorer

Known issues with pull request:

None known

Change log entries:

For Developers:

• UIAHandler.customAnnotations.CustomAnnotationTypesCommon, UIAHandler.customProps.CustomPropertiesCommon, NVDAObjects.UIA.excel.ExcelCustomProperties and NVDAObjects.UIA.excel.ExcelCustomAnnotationTypes are no longer singletons - their get method has been removed.

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English
• Security precautions taken.