Material not updating when param in Attribute node is changed via Python

Question

I have a Material node, it contains the default BSDF Shader whose color is fed via an Attribute Node. The Type is Object, and Attribute Node's Name is custom_color.

I would like to change this attribute with my Python script.

It creates a panel called Custom Panel that you can access under an object's Object Properties.

Changing the color via the color picker will refresh the material in the viewport correctly.

However, when I click the button "White", the color picker will change correctly to white, but the object in the viewport will not update, it is still the color it had when I selected it with the color picker.

Of course, save and load the scene and the color will be white. I must be missing some funky update or refresh the color picker does. How do I execute an update or refresh?

import bpy

# First I define a per object attribute: custom_color

bpy.types.Object.custom_color = bpy.props.FloatVectorProperty(
    name="Custom Color",
    subtype='COLOR',
    default=(1.0, 1.0, 1.0),
    min=0.0,
    max=1.0,
)

# Here I have the function for the button to press that is supposed to set the color of custom_color

class OBJECT_OT_SetCustomColor(bpy.types.Operator):
    """Sets the custom color via default color buttons"""
    bl_idname = "object.set_custom_color"
    bl_label = "Set Custom Color"

    color : bpy.props.FloatVectorProperty(
        subtype='COLOR',
    )

    def execute(self, context):
        bpy.context.object.custom_color = self.color
        return {'FINISHED'}

# Here I have the created panel, note that it has a color picker, and a button that sets the color of custom_color.
# What I want are couple color preset buttons the user can click.

class OBJECT_PT_CustomPanel(bpy.types.Panel):
    bl_label = "Custom Panel"
    bl_idname = "OBJECT_PT_custom_panel"
    bl_space_type = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    bl_context = "object"

    def draw(self, context):
        layout = self.layout
        obj = bpy.context.active_object

        # Color picker UI element
        layout.prop(obj, "custom_color", text="Custom Color")

        layout.operator("object.set_custom_color", text="White").color = (1, 1, 1)

def register():
    bpy.utils.register_class(OBJECT_OT_SetCustomColor)
    bpy.utils.register_class(OBJECT_PT_CustomPanel)

def unregister():
    bpy.utils.unregister_class(OBJECT_OT_SetCustomColor)
    bpy.utils.unregister_class(OBJECT_PT_CustomPanel)
    
register()

Answer 1

For some reason you need to define an update function for it to refresh or update. In this case I added an anonymous function that does nothing using lambda keyword. So I simply added 1 line to your code update=lambda self, context: None

import bpy

# First I define a per object attribute: custom_color

bpy.types.Object.custom_color = bpy.props.FloatVectorProperty(
    name="Custom Color",
    subtype='COLOR',
    default=(1.0, 1.0, 1.0),
    min=0.0,
    max=1.0,
    update=lambda self, context: None
)

# ... the rest is the same code