Allow discard_init_args_on_class_path_change to handle more nested contexts

[speediedan]

What does this PR do?

Fixes #247

While a subclass_spec can be either a dict or Namespace

jsonargparse/jsonargparse/typehints.py

Lines 790 to 795 in ac790ba

	def is_subclass_spec(val):
	is_class = isinstance(val, (dict, Namespace)) and 'class_path' in val
	if is_class:
	keys = getattr(val, '__dict__', val).keys()
	is_class = len(set(keys)-{'class_path', 'init_args', 'dict_kwargs', '__path__'}) == 0
	return is_class

when entering ActionTypeHint.discard_init_args_on_class_path_change:

jsonargparse/jsonargparse/typehints.py

Lines 295 to 310 in ac790ba

	@staticmethod
	def discard_init_args_on_class_path_change(parser_or_action, prev_cfg, cfg):
	if isinstance(prev_cfg, dict):
	return
	keys = list(prev_cfg.keys(branches=True))
	num = 0
	while num < len(keys):
	key = keys[num]
	prev_val = prev_cfg.get(key)
	val = cfg.get(key)
	if is_subclass_spec(prev_val) and is_subclass_spec(val):
	action = parser_or_action
	if not isinstance(parser_or_action, ActionTypeHint):
	action = _find_action(parser_or_action, key)
	if isinstance(action, ActionTypeHint):
	discard_init_args_on_class_path_change(action, prev_val, val)

jsonargparse.typehints.discard_init_args_on_class_path_change below currently assumes any previous value for a nested subclass will already have been cast as a Namespace:

jsonargparse/jsonargparse/typehints.py

Lines 934 to 942 in ac790ba

	def discard_init_args_on_class_path_change(parser_or_action, prev_val, value):
	if prev_val and 'init_args' in prev_val and prev_val['class_path'] != value['class_path']:
	parser = parser_or_action
	if isinstance(parser_or_action, ActionTypeHint):
	sub_add_kwargs = getattr(parser_or_action, 'sub_add_kwargs', {})
	parser = ActionTypeHint.get_class_parser(value['class_path'], sub_add_kwargs)
	del_args = {}
	for key, val in list(prev_val.init_args.__dict__.items()):
	action = _find_action(parser, key)

with L941 resulting in:

argparse.ArgumentError: Parser key "some_class":
  Problem with given class_path '__main__.CustomModule':
    - 'dict' object has no attribute 'init_args'

Right now, nested generic dict configurations like the repro case I include below don't trigger the subclass_spec_as_namespace Namespace wrapping that jsonargparse.typehints.discard_init_args_on_class_path_change requires when removing overridden subclass spec configuration in this context.

With this PR's minor patch to jsonargparse.typehints.discard_init_args_on_class_path_change, this use case can be accommodated. This PR also adds a test that covers the expanded support.

## Before submitting

- [x] Did you read the [contributing guideline](https://github.com/omni-us/jsonargparse/blob/master/CONTRIBUTING.rst)?
- [x] Did you update **the documentation**? (readme and public docstrings)
- [x] Did you write **unit tests** such that there is 100% coverage on related code? (required for bug fixes and new features)
- [x] Did you verify that new and existing **tests pass locally**?
- [x] Did you make sure that all changes preserve **backward compatibility**?
- [x] Did you update **the CHANGELOG**? (not for typos, docs, test updates, or minor internal changes/refactors)

[mauvilsa]

Sorry for not looking at this sooner. Thank you very much for contributing!

Please add an entry to the changelog.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change

Comparison is base (14b4842) 100.00% compared to head (cb2d122) 100.00%.

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Additional details and impacted files

@@            Coverage Diff            @@
##            master      #248   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           20        20           
  Lines         5189      5190    +1     
=========================================
+ Hits          5189      5190    +1     

Flag	Coverage Δ
py3.10	87.93% <100.00%> (+<0.01%)	⬆️
py3.10_all	99.88% <100.00%> (+<0.01%)	⬆️
py3.6	87.57% <100.00%> (+<0.01%)	⬆️
py3.6_all	99.63% <100.00%> (+<0.01%)	⬆️
py3.7	87.59% <100.00%> (+<0.01%)	⬆️
py3.7_all	99.80% <100.00%> (+<0.01%)	⬆️
py3.8	87.91% <100.00%> (+<0.01%)	⬆️
py3.8_all	99.84% <100.00%> (+<0.01%)	⬆️
py3.9	87.91% <100.00%> (+<0.01%)	⬆️
py3.9_all	99.86% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
jsonargparse/typehints.py	100.00% <100.00%> (ø)

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