Having a default of None will allow for consistency within the ViewStateValue object. All other attributes default to None, but selected_options does not get set if the input is an empty list (ex Checkbox). This results in an AttributeError.

Reproducible in:

The Slack SDK version

slack-bolt==1.4.4

Python runtime version

Python 3.8.3

OS info

OS info
ProductName:	Mac OS X
ProductVersion:	10.15.7
BuildVersion:	19H524
Darwin Kernel Version 19.6.0: Tue Jan 12 22:13:05 PST 2021; root:xnu-6153.141.16~1/RELEASE_X86_64

Steps to reproduce:

(Share the commands to run, source code, and project settings (e.g., setup.py))

1. Instantiate a ViewStateValue with selected_options as an empty list
2. See below

Expected result:

selected_options should default to None

Actual result:

>>> d = {"selected_options": []}
>>> v = ViewStateValue(**d)
>>> v
<slack_sdk.ViewStateValue>
>>> v.selected_channel is None
True
>>> v.selected_options is None
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'ViewStateValue' object has no attribute 'selected_options'

Requirements

For general questions/issues about Slack API platform or its server-side, could you submit questions at https://my.slack.com/help/requests/new instead. 🙇

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