How can I temporarily disable a handler?

Question

I'm using a regular save_post handler for my add-on and I'd like to allow the user to turn it off occasionally. Removing the function from handlers.save_post list and re-append seems expensive. Is there any clever trickery to manage that easily? What's a reliable way to temporarily disable the handler?

import bpy

def my_save_handler(dummy):
    print ("Blend file has been saved.")

def register():
    bpy.app.handlers.save_post.append(my_save_handler)
def unregister():
    bpy.app.handlers.save_post.remove(my_save_handler)

if __name__ == "__main__":
    register()

This is a follow-up question emerged from: Modify the Save project function

Answer 1

One simple way is to add an if-statement to the body of the handler in order to determine whether the rest of the code should execute by using one additional Bool or EnumProperty declared in the preferences of your add-on:

class MYTOOL_AP_preferences(bpy.types.AddonPreferences):
    ...
    state: bpy.props.BoolProperty(name="Switch")
    ...

def my_save_handler(dummy):
    if state:
        ...

Demo on how the user can disable the handler via Preferences using one EnumProperty:

import bpy

bl_info = {"name": "Stats Add-on", "blender": (2, 82, 0), "category": "System"}

class MYTOOL_AP_preferences(bpy.types.AddonPreferences):
    # this must match the add-on name, use '__package__'
    # when defining this in a submodule of a python package.
    bl_idname = __name__
    
    state: bpy.props.EnumProperty(name="Switch", default = 'ON',
        items=(("ON", "On", "", 1), ("OFF", "Off", "", 2)))
    
    def draw(self, context):
        self.layout.row().prop(self, "state", expand=True)

def my_save_handler(dummy):
    if bpy.context.preferences.addons[__name__].preferences.state == 'ON':
        print ("Blend file has been saved.")
    
def register():
    bpy.utils.register_class(MYTOOL_AP_preferences)
    bpy.app.handlers.save_post.append(my_save_handler)

def unregister():
    bpy.app.handlers.save_post.remove(my_save_handler)
    bpy.utils.unregister_class(MYTOOL_AP_preferences)

if __name__ == "__main__":
    register()