create driver driven by a new custom property

In this Blender StackExchange discussion we discuss a workflow of creating several Drivers that have new Custom Properties that allow for linked library overrides on modifier parameters. It is not a trivial task and there is a python script that would be nice to have in the RMB menu for modifier properties.

The python solution is partially represented by the following, but should be a RMB menu action when hovering over a property.

# ========================================================================
# Function declarations
# ========================================================================

def get_property_name(obj,data_path) -> str:
    s = data_path
    i = s.find('.')
    data_path_1 = ""
    data_path_2 = data_path
    if i > 0:
        ri = s.rindex('.')
        data_path_1 = '.' + s[0:ri]
        data_path_2 = s[ri+1:len(s)]
    data = eval("bpy.context.object" + data_path_1)
    print('get_property_name data=',data)
    return data.rna_type.properties[data_path_2].name if hasattr(data, data_path_2) else ''

def get_property_type(obj,data_path) -> type:
    print(obj,'....',data_path)
    #getattr(obj,data_path)
    return type(obj.path_resolve(data_path))

def clear_drivers(obj, data_path, index):
    if obj.animation_data is None:
        return
    drivers = obj.animation_data.drivers

    for d in drivers:
        if d.data_path != data_path:
            continue
        if index < 0:
            for idx in range(-1,3):
                obj.driver_remove(d.data_path, idx)
        else:
            obj.driver_remove(d.data_path, index)

def create_driver(fcurve, obj, custom_prop):
    d = fcurve.driver
    v = d.variables.new()
    v.name = "myvar"

    target = v.targets[0]
    target.id_type = 'OBJECT'
    target.id = obj
    target.data_path = '["' + custom_prop + '"]'
    d.expression = "myvar"
    print('create_driver for ',custom_prop)

# ========================================================================
# Initialize properties from first keying set
# ========================================================================
def keySetToDrivers():
    if(len(bpy.context.scene.keying_sets) == 0):
        print('First right click property and select "Add to Keying Set".')
        return
    ksPaths = bpy.context.scene.keying_sets[0].paths
    if(len(ksPaths)==0):
        print('First right click property and select "Add to Keying Set"')
        bpy.ops.anim.keying_set_remove()
        return

    for ks in ksPaths:   
        obj = bpy.data.objects[ks.id.name] # get the object for the custom props
        ks_use_entire_array = ks if ks.use_entire_array else False
        if(ks_use_entire_array):print('ks_use_entire_array for',ks.id.name)
        DATA_PATH = ks.data_path
        INDEX = -1 if ks_use_entire_array else ks.array_index

        CUSTOM_PROPERTY = get_property_name(obj,DATA_PATH)

        if ( CUSTOM_PROPERTY == '' ): continue # skip if error return

        print('DATA_PATH',DATA_PATH)

        if INDEX < 0:
            for idx in range(-1,3):
                custom_prop = CUSTOM_PROPERTY + ' [' + str(idx) + ']'
                if custom_prop in obj:
                    del obj[custom_prop]
        else:
            CUSTOM_PROPERTY = CUSTOM_PROPERTY + ' [' + str(INDEX) + ']'
            if CUSTOM_PROPERTY in obj:
                del obj[CUSTOM_PROPERTY]

        # ========================================================================
        # Add property and driver
        # ========================================================================

        if CUSTOM_PROPERTY in obj:
            print("WARNING: to prevent overwriting custom property, substituting with data_path name")
            continue

        clear_drivers(obj, DATA_PATH, INDEX)
        print('CUSTOM_PROPERTY',CUSTOM_PROPERTY)
        p = bpy.props.BoolProperty(name=CUSTOM_PROPERTY, default=0, options={'ANIMATABLE','LIBRARY_EDITABLE'}, override={'LIBRARY_OVERRIDABLE'}, tags=set())
        initVal=0
        t=get_property_type(obj, DATA_PATH)
        print('get_property_type',t)
        if( t is type(bool())):
            print('type is bool (int)')
            initVal=0
        elif( t is type(int())):
            print('type is int')
            initVal=0
        elif( t is type(float())):
            print('type is float')
            initVal=0.0
        elif( t is type(str())):
            print('type is string')
            initVal=''

        obj[CUSTOM_PROPERTY] = initVal # you can add the custom property like this
        ui = obj.id_properties_ui(CUSTOM_PROPERTY)
        ui.update(description=DATA_PATH)
        if( t is type(bool())):
            print('type is bool')
            ui.update(default=0,min=0,max=1)
        elif( t is type(int())):
            print('type is int')
            ui.update(default=0,min=0)
        elif( t is type(float())):
            print('type is float')
            ui.update(default=0,min=0.0)
        elif( t is type(str())):
            print('type is string')
            #ui.update(default=0,min=0)
        #ui.update(default=0,min=0)
        obj.property_overridable_library_set('["'+CUSTOM_PROPERTY+'"]', True)

        fcurve_or_list = obj.driver_add(DATA_PATH, INDEX)

        if type(fcurve_or_list) is list:
            for fcurve in fcurve_or_list:
                create_driver(fcurve, obj, CUSTOM_PROPERTY)
        else:
            create_driver(fcurve_or_list, obj, CUSTOM_PROPERTY)

    bpy.ops.anim.keying_set_remove() # clean up

keySetToDrivers()