MAYA121636 handle scope for read-only transform

[pierrebai-adsk]

• Implement Transform3dRead for scope prim.
• Add a Transform3dHandler that creates that implementation for scopes.
• Add unit tests.

[pierrebai-adsk]

Implementation of the UFE interface that went in UFE 0.4.25. (Maya is now at 0.4.30.)

[ppt-adsk]

Can have a look at the latest discussion in the original issue:
#2085

[ppt-adsk]

Looks good, thanks for making this change, just the private inheritance I'm wondering about.

[ppt-adsk]

On second thought, I think we need an addition and a change to the tests:

1. Need to add a parent -relative test. It's the trivial case, but it still needs a test :)
2. The new tests need to be protected by a ufeSupportFixLevel() decorator, so that they will only run if Maya has the proper support. You can add the fixLevel in your Maya pull request. See
   

   maya-usd/test/lib/ufe/testGroupCmd.py

   Line 926 in 387a1fa

   @unittest.skipUnless(mayaUtils.ufeSupportFixLevel() >= 5, 'Requires Maya xform command fix.')

[pierrebai-adsk]

2. The new tests need to be protected by a ufeSupportFixLevel() decorator, so that they will only run if Maya has the proper support.  You can add the fixLevel in your Maya pull request.  See
   https://github.com/Autodesk/maya-usd/blob/387a1fa6c11f8a7349d7ebe353e55382603e2347/test/lib/ufe/testGroupCmd.py#L926

I'm thinking a bit more about the UFE fix level: it seems that it does not work well with back-porting. We may not backport everything to an older version of Maya. so if we backport a fix at fix-level N, we may not have ported the fixes related to fix-level N-1, N-2, etc. It would be better if we the fix-level were instead a fix-features list. For now I'll add a fix level.

[ppt-adsk]

2. The new tests need to be protected by a ufeSupportFixLevel() decorator, so that they will only run if Maya has the proper support.  You can add the fixLevel in your Maya pull request.  See
   https://github.com/Autodesk/maya-usd/blob/387a1fa6c11f8a7349d7ebe353e55382603e2347/test/lib/ufe/testGroupCmd.py#L926

I'm thinking a bit more about the UFE fix level: it seems that it does not work well with back-porting. We may not backport everything to an older version of Maya. so if we backport a fix at fix-level N, we may not have ported the fixes related to fix-level N-1, N-2, etc. It would be better if we the fix-level were instead a fix-features list. For now I'll add a fix level.

There is no fix level for backports. Fix level only exists for master, to protect plugin code from execution using a Maya that is inappropriate. For previous versions of Maya, you can assume the plugin code is already being executed using Maya master until you put in your fix into the previous version of Maya. Once that's done, you can enable the test for that previous Maya version in the plugin.

The point of fix level is to protect against execution within the time scope of a Maya preview release, when no UFE version number is appropriate. In such a case, you cannot rely on the Maya preview release number, or the Maya version, or the UFE version.