Python Toolbox: Only validate when you press run?

[AlfredBaldenweck]

I'm running into an issue where the standard validation is just taking waaaay too long (Describing the input) and I really just need it to validate when I press Run, not beforehand.

That is, if there's an error, only tell me when I press Run.

Has anyone figured out a way to do this?

[HaydenWelch]

You can just rename your validation function so it's not called in the validation loop and run it at the top of your execute function, something like this:

import arcpy
import time

class Tool:
    
    ... # other methods
    
    def validateParameters(self, parameters):
        # Expensive validation goes here
        time.sleep(5)
        
        # Randomly fail validation
        if time.time() % 2 == 0:
            arcpy.AddError("Validation failed")
            return False
        
        arcpy.AddMessage("Validation complete")
        return True
    
    def execute(self, parameters, messages):
        # Expensive execution goes here (after run)
        if not self.validateParameters(parameters):
            arcpy.AddError("Validation failed")
            return
        return