Fixed cmd2 bypassing NO_COLOR and allow_style when setting prompt-toolkit's color depth.

[kmvanbrunt]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.59%. Comparing base (d35f7d7) to head (2cb95e2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1706      +/-   ##
==========================================
- Coverage   99.60%   99.59%   -0.02%     
==========================================
  Files          23       23              
  Lines        5894     5900       +6     
==========================================
+ Hits         5871     5876       +5     
- Misses         23       24       +1     

Flag	Coverage Δ
unittests	99.59% <100.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

[tleonhardt]

It is a common pattern for subclasses of cmd2.Cmd to configure properties like self.allow_style in their __init__ before calling super().__init__(). Doing so here will crash the application because main_session has not been instantiated yet. Using getattr would makes this setter safe at any point in the lifecycle, i.e.:

if getattr(self, "main_session", None) is not None:
    self.main_session.color_depth = pt_resolve_color_depth()

[kmvanbrunt]

This is true for a few of our settables. They expect certain instance members to exist before than can safely be set.

1. allow_style
2. always_prefix_settables
3. traceback_show_locals
4. traceback_width

[tleonhardt]

We should either attempt to ruggedize their use like I was suggesting above or do a very good job of documenting that these are special and certain instance members need to exist before they can be safely set (likely by saying don't set them before calling parent class dunder init).

[kmvanbrunt]

I think it's best to leave the code alone. __init__() functions are meant to establish the baseline state for an instance. Setting a parent's instance variables before calling super().__init__() doesn't seem safe since those values could be overwritten by __init__().