Update Parameters in Toolbox after refreshing selection

Question

I have a python toolbox with a 'GPFeatureLayer' parameter, and a 'GPString' parameter.  The string field is a dropdown populated with the unique values of an ID field in my feature layer.  If there is a selection on the feature layer, the dropdown value list is correctly populated using just that selection.

If the user updates their selection, the list does not update.  Clicking the refresh arrows next to "The input has a selection. Records to be processed: X" does not call updateParameters().  The user must select a new feature layer and the reselect the old feature layer to force the update, or close the tool and reopen it. This is not the desired workflow.

Is there any way to force a parameter update when refreshing the selection? Can ESRI staff perhaps help me find the clearest language to make a new Idea post to ask for this functionality?  Something like Geoprocessing Tool Selection Refresh should call updateParameters() in python toolbox. Thanks.

Bsmith_DPW · Answer

I created the Idea here, thank you.

https://community.esri.com/t5/arcgis-pro-ideas/selection-refresh-should-call-updateparameters/idi-p/1392004

abaldenweck@blm.gov_BLM_EGIS · Answer

I would vote for an idea to make that refresh button call updateParameters().

Bsmith_DPW · Answer

I was able to craft a workaround.  I still think that clicking the refresh icon should call updateParameters(), but for anyone else encountering this issue in the meantime

* Add a new GPBoolean parameter, named something like "Click here to force update selection"
* Compare the ID value to its own filter list, and update if necessary

def updateParameters(self, parameters):

#get list of OIDs
        oidfield = arcpy.Describe(parameters[0].value).OIDFieldName
        oidlist = [row[0] for row in arcpy.da.SearchCursor(parameters[0].value, oidfield)]

#whenever feature layer is defined, populate list of IDs
        if parameters[0].altered and not parameters[0].hasBeenValidated:
            #and populate the dropdown
            parameters[1].filter.list = oidlist
            parameters[1].value = oidlist[0]

#make sure that list of IDs is always up to date, and replace any bad values
        if parameters[1].value not in oidlist:
            parameters[1].filter.list = oidlist
        if parameters[1].value not in parameters[1].filter.list:
            parameters[1].value = parameters[1].filter.list[0]

return