[PDG] Parm expressions on HDAProcessor prevent generation

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I've got an HDA that loads geo, performs a bunch of actions, then writes it back to disk. I'd like to use the HDA Processor to handle this but I've run into some issues with Python parameter expressions on the HDA, seemingly caused by the "hdap_*" prefix.

Quick example: on my HDA I have 2 parms called 'extratx' and 'finaltx', with a Python expression running on 'finaltx' that reads the value of 'extratx', performs some additional work, then returns the value:

node = hou.pwd()
extratx = node.parm('extratx').eval()

return(extratx*3)

When I plug that HDA into an HDA Processor and Generate work items though, I get an error along the lines of

Unable to evaluate expression (
Traceback (most recent call last):
File "<stdin>", line 3, in expression
AttributeError: 'NoneType' object has no attribute 'eval'
(/obj/topnet1/hdaprocessor1/hdap_finaltx)).

It looks like the expression is trying to evaluate 'extratx', which should now be 'hdap_extratx'. I thought these parm references were supposed to be updated on the fly by the HDA Processor, so I must be doing something wrong with my setup.

I'm aware that hython will instantiate a fresh copy of the HDA when it cooks, but if I can't generate the work items I can't get that far with it.

Any thoughts? My issue is very similar to this post:

https://www.sidefx.com/forum/topic/71498/ [www.sidefx.com]

and related to this one as well:

https://www.sidefx.com/forum/topic/72664/?page=1#post-312738 [www.sidefx.com]

but I haven't been able to solve my problem from those discussions. Any additional help would be appreciated.
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