AY-6654 Look: Fix None values in collecting and applying attributes

[BigRoy]

Changelog Description

This fixes a case where looks failed to apply due to None values being present in the collected attributes.
These will now be ignored in collected. There's an edge case where Maya returns None for string attributes that have no values set - those are captured now explicitly to just "" to still collect and apply them later.

Existing looks will now also apply correctly with None value in their look attributes, but the attributes with None values will be ignored with a warning.

Additional info

Testing notes:

1. Load a model reference
2. Create a string attribute, e.g. test
3. Do not set any value for it.
   • Maya will return None for this attribute, e.g. select the object and run:

from maya import cmds
print(cmds.getAttr(".test"))

It will print None.
4. Publish the look for this mesh
5. The published .json file should have attribute value for test set to ""

To test the 'backwards compatible fix':

• Publish the same look with develop branch. The value will be null in the .json file.`
• OR, just open the last published .json file, and edit the "" value to null

Then, confirm that applying the look succeeds without errors but with a warning regarding the None value when applying with this PR. For example in my test run it logged:

// Warning: ayon_maya.api.lib : Skipping setting |_GRP|cube_GEO.test with value 'None'

[LiborBatek]

It all works speaking of the new way of treating the occasion when no any entry in the custom attribute present...so all good on this front!

I have issue when trying the "backward compatible" steps as it throws an error when None value present in the JSON so I dont get any warning only instead.

aka it seems that it still fails... (even tho my asset got the look assigned anyway)

// Warning: ayon_maya.api.lib : Skipping setting |screwD_modelMain_01_:_GRP|screwD_modelMain_01_:model_GRP|screwD_modelMain_01_:Body_GEO.custom with value 'None'
# Traceback (most recent call last):
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\tools\mayalookassigner\app.py", line 286, in on_process_selected
#     assign_look_by_version(
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\api\lib.py", line 1889, in assign_look_by_version
#     apply_shaders(relationships, shader_nodes, nodes)
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\api\lib.py", line 2027, in apply_shaders
#     apply_attributes(attributes, nodes_by_id)
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\api\lib.py", line 1738, in apply_attributes
#     set_attribute(attr, value, node)
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\api\lib.py", line 1694, in set_attribute
#     kwargs = ATTRIBUTE_DICT[value_type]
# KeyError: 'NoneType'

[BigRoy]

It all works speaking of the new way of treating the occasion when no any entry in the custom attribute present...so all good on this front!

I have issue when trying the "backward compatible" steps as it throws an error when None value present in the JSON so I dont get any warning only instead.

aka it seems that it still fails... (even tho my asset got the look assigned anyway)

// Warning: ayon_maya.api.lib : Skipping setting |screwD_modelMain_01_:_GRP|screwD_modelMain_01_:model_GRP|screwD_modelMain_01_:Body_GEO.custom with value 'None'
# Traceback (most recent call last):
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\tools\mayalookassigner\app.py", line 286, in on_process_selected
#     assign_look_by_version(
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\api\lib.py", line 1889, in assign_look_by_version
#     apply_shaders(relationships, shader_nodes, nodes)
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\api\lib.py", line 2027, in apply_shaders
#     apply_attributes(attributes, nodes_by_id)
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\api\lib.py", line 1738, in apply_attributes
#     set_attribute(attr, value, node)
#   File "c:\Work\REPO\ayon-maya\client\ayon_maya\api\lib.py", line 1694, in set_attribute
#     kwargs = ATTRIBUTE_DICT[value_type]
# KeyError: 'NoneType'

That's exactly the error this PR should solve. It applies the shaders yes, but fails to apply all attributes.
Did you test that "applying" with the null in the JSON file with this PR enabled?
(You will need to launch Maya while in this branch! So restart if you hadn't)

[BigRoy]

Sorry, somehow my previous push of the commit failed. It was missing this: fc52bb1

Try again.

[LiborBatek]

Now all good and no errors thrown...

Just that Warning message as mentioned in testing steps.

Good to go!