Link to issue number:

None

Summary of the issue:

It is possible to register a callback on hwIo.IoBase to catch read errors. However, if this is a callback on a driver and the driver closes the device, the device keeps a reference to the callback on the driver. This causes a circular reference.

Description of user facing changes

Possibly less unreachable object errors

Description of development approach

Similar to _onReceive, ensure that onReadError is set to None when closing the device.

Testing strategy:

Tested locally with a driver providing an onReadError callback, ensured that the garbage collector could correctly cleanup resources.

Known issues with pull request:

None known

Change log entries:

This was only noticeable in the log, it is not user visible.

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.