Hii All,
I was just trying to pass the search_default in the button which opens up a action(type='action').
For example -> this field is present in the search with filter_domain.I tried by removing filter also.Now my this button is inside the child form view
Like 
1) Opened a form view from that form view by using a smart button opening another models tree view.
2)Opening the second form view by clicking on the tree view.
3) Now this tree view also have one smart button with the action and context mentioned above but this time its taking active id of the first form view not the recently opened form view.
I'm not sure why it is behaving it like this.In odoo 10 it was taking active id as currently opened form view i found one work around by adding same context in the window action then its working perfectly fine like taking current form opened id as active id ({"search_default_field_name": active_id}).But i want to know why its behaviour has changed in odoo v15