v5 errors when using S(Q) with a multiplicity model such as onion

[RichardHeenan]

after adding an S(Q) to say onion, when I change the number of shells I get:

• ERROR: Traceback (most recent call last):
  File "C:\sasview5\sasview\src\sas\qtgui\Perspectives\Fitting\FittingWidget.py", line 2625, in onMainParamsChange
  self.kernel_module.setParam(parameter_name, value)
  File "C:\sasview5\sasmodels\sasmodels\sasview_model.py", line 513, in setParam
  raise ValueError("Model does not contain parameter %s" % name)
  ValueError: Model does not contain parameter n_shells

I suspect that once S(Q) is included the F(Q) is then also not being computed correctly, as the effective radius in S(Q) is wrong, only including the first shell, so suspect n_shells is being passed as zero.

[also can someone please add a new milestone, for 5.0.5 ? ]

[pkienzle]

Maybe something in the GUI code which is not treating n_shells as a "multiplicity" parameter. The underlying onion@hardsphere model in sasmodels does define n_shells as a control parameter which the sasview_model wrapper should be turning into a multiplicity parameter. I think that means that the multiplicity parameter n_shells should not be modified as a parameter in the table, but instead a new model created with the correct number of shells as the multiplicity.

[butlerpd]

I think this is part of a larger issue of how the GUI handles control parameters from sasmodels. See for example SasView/sasmodels#396 and #1897. Unfortunately this larger issues does not seem to have been noted in time to fix for this release.

[krzywon]

As noted in #2647, this was fixed in v5.0.6. Closing.