Added unit handling to STEP import and export

[jmwright]

@adam-urbanczyk @lorenzncode This fixes a long-standing issue where things are at the wrong scale when exchanging STEP files because CadQuery did not use OCCT's units mechanism.

Fixes #1449, fixes #1829

[jmwright]

Related issues that should be closed after this is merged: #1829 #1449

[codecov]

Codecov Report

❌ Patch coverage is 96.55172% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.62%. Comparing base (f86ff79) to head (250032c).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
cadquery/assembly.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2023   +/-   ##
=======================================
  Coverage   95.61%   95.62%           
=======================================
  Files          30       30           
  Lines        8881     8893   +12     
  Branches     1311     1311           
=======================================
+ Hits         8492     8504   +12     
  Misses        240      240           
  Partials      149      149           

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[adam-urbanczyk]

Thanks for picking this up @jmwright , this is very needed! Could you also add another option to export (e.g. outputUnit : STEPUnitLiterals | None = None) that would control the output unit and make unit control the document unit too? The default behavior being document unit == output unit? Cf. xstep.cascade.unit and write.step.unit OCCT options.

[adam-urbanczyk]

More context: https://dev.opencascade.org/content/differences-behavior-units-xstepcascadeunit-and-stepcontrolwriter-75-76

[jmwright]

@adam-urbanczyk Is the current implementation that you had in mind?

[adam-urbanczyk]

Yes, thanks! Just give me some time to review.

[adam-urbanczyk]

So I found a few things:

1. It would be nice to support mm on top of MM
2. I think import should reply on "cascade.unit"
3. Would it be possible to support xbf an xml too?

[jmwright]

@adam-urbanczyk Are the mypy errors I'm getting now related to the ones you are getting on the nurbs PR?

[adam-urbanczyk]

Not really, new release of mypy got more strict (as it usually does).

[adam-urbanczyk]

@jmwright do you mind if I'm going to try to add units to xbf and xml import/export too? Or shall we try this in another PR?

[jmwright]

do you mind if I'm going to try to add units to xbf and xml import/export too?

@adam-urbanczyk Feel free, if you would like. However, it's a slightly different mechanism for setting the units for non-STEP formats, if I understand correctly.

[adam-urbanczyk]

I added (STEP only, not sure how to make this work for xbf/xml) unit handling for export/load. @lorenzncode do you want to take a look, or shall I merge?

[adam-urbanczyk]

@lorenzncode thanks for taking a look! I think I resolved all of the issues.

[lorenzncode]

Thanks @adam-urbanczyk @jmwright ! I found one more doc issue to check.

[adam-urbanczyk]

Alright, merging. Thanks a lot for the implementation @jmwright and reviewing @lorenzncode!