Custom AddRuntimeMessage instead of "Input fails to collect data"

[magicteddy]

Prompt_Plural is a method that does not belong to an IGH_Component, but a GH_PersistentParam. I guess you would see your messages if the elements are set from a param, but not done from a component ? In other words error messages generated by the parameter don’t rise up to the component level.

Automatic update of ValueList only when connected

I think I got this to work as intended. The problem of storing keys and values is that we’d need to be able to access input data outside of SolveInstance, which seems only possible using VolatileData. However this requires to deal with IGH_Structure so I went another way… I made all three parameters optional, but added the runtime messages inside SolveInstance. protected override void SolveInstance(IGH_DataAccess DA) { // Set Keys and Items keys.Clear(); …

I did this but inside SolveInstance, not inside Prompt_Plural.

You could try to set the inputs of the component as optional, so the Input parameter xxx failed to collect data never shows up.

Then after DA.GetData(), test for your various error messages.
It seems you can access the runtime messages from an input param : Params.Input[0].RuntimeMessages()

Untested solution there, maybe a step in the right direction.