Problem with shader nested parameters in XSI? Workarounds?

[Andy Jones <andy(at)thefront.com>]

# I think this python code demonstrates a problem with parameter updates 
in XSI 5.1.
# What seems to happen is that when a datasource is removed from a 
shader parameter,
# the nested parameters don't get recreated until after the script has 
finished running.
# This is a problem because in a lot of scripts, I might want to replace 
shader inputs
# with hard-coded values.

# Instructions:  Run the script twice.  Ideally, the value of the red 
parameter
# of the diffuse input on the scene material's phong should be logged 
twice. 
# Instead, the red parameter is inaccessible, even after the shader 
input is
# disconnected, until the script has finished.

def LogRed(colorParam):
   try:
       # Attempt to read a value from red component
       Application.LogMessage(colorParam.red.Value)

   except:
       Application.LogMessage("Failed to retrieve red parameter")

       # Try to list the parameters (none get listed)
       for p in colorParam.Parameters:
           Application.LogMessage(p.FullName)
       

# Grab the diffuse input of the scene material
try:
   Application.SelectObj("Sources.Materials.DefaultLib.Scene_Material", 
"", "")
   scnMatPhongDiffuse = Application.Selection[0].surface.source.diffuse
except:
   Application.NewScene("", "")
   Application.SelectObj("Sources.Materials.DefaultLib.Scene_Material", 
"", "")
   scnMatPhongDiffuse = Application.Selection[0].surface.source.diffuse

# Connect and disconnect a shader every other run of the code and try to 
log red value
if (scnMatPhongDiffuse.Source == None):
   LogRed(scnMatPhongDiffuse)
   Application.LogMessage("Connecting shader to diffuse")
   scnMatPhongDiffuse.ConnectFromProgID("Softimage.txt2d-image-explicit.1")
else:
   Application.LogMessage("Disconnecting shader from diffuse")
   scnMatPhongDiffuse.Disconnect()
   LogRed(scnMatPhongDiffuse)

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