"ValueError: Sub-data not available" when trying to parse vendor VariableItem

[haku]

I am trying to reverse engineer a device with a bunch of vendor specific report formats. I think I might have found an issue in VariableItem when parsing vendor messages:

Traceback (most recent call last):
  File "/home/haku/src/usbhid-experiments/./test-parse.py", line 56, in <module>
    for usage, value in desc.parse_input_report(data).items():
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/haku/.cache/pyvenv-hid/lib/python3.12/site-packages/hid_parser/__init__.py", line 690, in parse_input_report
    return self._parse_report(self._input, data)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/haku/.cache/pyvenv-hid/lib/python3.12/site-packages/hid_parser/__init__.py", line 687, in _parse_report
    return self._parse_report_items(item_poll[data[0]], data[1:])
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/haku/.cache/pyvenv-hid/lib/python3.12/site-packages/hid_parser/__init__.py", line 669, in _parse_report_items
    parsed[item.usage] = item.parse(data)
                         ^^^^^^^^^^^^^^^^
  File "/home/haku/.cache/pyvenv-hid/lib/python3.12/site-packages/hid_parser/__init__.py", line 433, in parse
    if hid_parser.data.UsageTypes.LINEAR_CONTROL in self.usage.usage_types or any(
                                                    ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/haku/.cache/pyvenv-hid/lib/python3.12/site-packages/hid_parser/__init__.py", line 237, in usage_types
    usage_page = hid_parser.data.UsagePages.get_subdata(self.page)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/haku/.cache/pyvenv-hid/lib/python3.12/site-packages/hid_parser/data.py", line 159, in get_subdata
    raise ValueError(msg)
ValueError: Sub-data not available

I have a script that reproduces the issue here: https://github.com/haku/usbhid-experiments/blob/main/test-parse.py

The issue appears to be that hid_parser.data.UsagePages.get_subdata(page) fails with this exception for any value of page within the VENDOR_PAGE range. While this library's test cases in test_parse.py do test parsing vendor reports, all the data types defined are arrays which have a different decode code path.

I am still learning my way around this library so not entirely sure what the fix should be, but I am happy to spend some more time figuring it out if that would be helpful for you?