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ni / nimi-python

Python bindings for NI Modular Instrument drivers.
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APIs allow repeated capabilities to access attributes and methods that don't support them #2038

Open ni-jfitzger opened 7 months ago

ni-jfitzger commented 7 months ago

Description of issue

As of nimi-python 1.4.7, the way repeated capabilities work is thus:

  1. When a _RepeatedCapabilities object, such as Session.channels, is accessed, it returns a _SessionBase object with _SessionBase.repeated_capability updated, based on what's passed to index operator [].
  2. When setting an attribute or calling a method using a repeated capability, _SessionBase.repeated_capability is passed to the method or SetAttribute method.

_SessionBase is one big collection of properties and methods that support repeated capabilities, with no distinction of which repeated capabilities are supported. As an example, the nifgen API will allow a user to set an attribute that supports the data_marker repeated capability with the script_trigger repeated capability. Because we allow this, the user may be puzzled when they get back an error.

marcoskirsch commented 7 months ago

When we first developed nimi-python, we didn't have metadata stating what driver functions/attributes supported which repeated capabilities.

But now we do.

A better design would be, in my opinion, to generate a Channel, Pin, MarkerEvent, etc. class with only those functions and attributes that apply. The repeated capabilities "container" would return one of these, rather than a _SessionBase.

This is not a trivial change to make though.

ni-jfitzger commented 7 months ago

Agreed, this would be a major change.

marcoskirsch commented 7 months ago

FWIW, I think the title of this issue makes the problem seem bigger than it really is.

It's true that the Python bindings will allow the client to call into the driver with an invalid set of arguments, but the driver runtime will still catch it and report a helpful error. It's just that we could improve on it and make it impossible to call the driver runtime in such way.

bkeryan commented 7 months ago

Changing the repeated capability object types would have more value if you added type hints. :) Then it would affect which properties show up in autocomplete.

ni-jfitzger commented 7 months ago

FWIW, I think the title of this issue makes the problem seem bigger than it really is.

Perhaps, but I' m not sure how else to word it. I did label it as an enhancement, rather than a bug.

It's true that the Python bindings will allow the client to call into the driver with an invalid set of arguments, but the driver runtime will still catch it and report a helpful error.

Yes, the driver should still error. I don't have an example handy comment on how helpful the error would be.

ni-jfitzger commented 7 months ago

Changing the repeated capability object types would have more value if you added type hints. :) Then it would affect which properties show up in autocomplete.

Yes, I think there's at least some overlap with #2019.