JQL function getValues method executes before validation

I wrote a custom JQL function plugin. While testing the plugin I found JqlFunction.getValues is called before JqlFunction.validate method, Due to this JqlFunction.getValues method executes 2 times. Here is the sequence of calls:

JqlFunction.getValues
JqlFunction.validate
JqlFunction.getValues (if there are no errors in validate method, it calls getValues again)

Ideally, JqlFunction.getValues should be called after JqlFunction.validate so that JQL logic execute once.