Improve Inheriting Workplane Fluent Methods

[pavpen]

• Updated Workplane.workplane(), Workplane.copyWorkplane(), Workplane.newObject() to return instances of a type that's based on the input parameters (such as self).
• Updated type hints to reflect that return types of fluent methods depend on the type of method arguments.
• Added a unit test to verify fluent methods in a derived class return instances of the derived class.

This is a pull request for issue #673.

[codecov]

Codecov Report

Merging #677 (9534a4c) into master (0325474) will increase coverage by 0.08%.
The diff coverage is 94.23%.

@@            Coverage Diff             @@
##           master     #677      +/-   ##
==========================================
+ Coverage   94.19%   94.28%   +0.08%     
==========================================
  Files          31       31              
  Lines        6689     6752      +63     
  Branches      725      727       +2     
==========================================
+ Hits         6301     6366      +65     
+ Misses        253      252       -1     
+ Partials      135      134       -1     

Impacted Files	Coverage Δ
cadquery/cq.py	91.05% <93.33%> (+0.24%)	⬆️
tests/test_cadquery.py	99.12% <100.00%> (+0.02%)	⬆️
cadquery/occ_impl/shapes.py	91.95% <0.00%> (+0.03%)	⬆️

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[marcus7070]

AppVeyor is failing a single test on 3.6, testOffset2D:

self.assertEqual(s.solids().size(), 4)
E       AssertionError: 1 != 4
tests\test_cadquery.py:4093: AssertionError

That test passes in all other CI envs, including Win 3.6 on Azure. @adam-urbanczyk this looks super weird, you might want to re-run that test? I don't have the permissions.

Although honestly, if it goes away after re-running that's going to be just as confusing. It's not like it's a network error...

[pavpen]

Hm. Yeah, these tests pass for me with Python 3.6.13 and 3.9.2 on Windows. It would be useful if someone is able to reproduce this error.

I can also push a whitespace change to force a re-run of the appveyor job. Or, is there a way to re-run it manually?

[marcus7070]

@adam-urbanczyk should have the permissions to re-run it manually, but he's busy at the moment. so feel free to do the whitespace change. Here is a (hopefully semi-permanent) link to the failing job for posterity: https://ci.appveyor.com/project/adam-urbanczyk/cadquery-icqj5/builds/38091458/job/k9pg21fnvqup9be5

[adam-urbanczyk]

If all fails, you can always close an reopen to trigger CI

[adam-urbanczyk]

One change request, otherwise looks good!

[jmwright]

I think once the requested change is done this will be ready to merge. Thanks @pavpen !

[adam-urbanczyk]

Thanks @pavpen !

[pavpen]

Thanks for the help! If you can figure out the differences between execution environments, it could help track the causes of the flaky unit tests.