Filtering socket in custom node tree inputs

Question

How can possible socket types be filtered in a custom node tree for group inputs and outputs? In node tree input/ output socket types is there a way to control which socket types appear? To test:

1. Copy and paste the following code into Blender's text editor.

from bpy.types import NodeTree, NodeSocket, NodeSocketInterface
from bpy.utils import register_class, unregister_class
import nodeitems_utils
from nodeitems_utils import NodeCategory, NodeItem

class TestSocket(NodeSocket):
    bl_label = "Example socket"
    
    def draw_color(self,context,node):
        return (0,.5,8,1)
    
    def draw(self,context,layout,node,text):
        layout.label(text=text)

class TestSocketInt(NodeSocketInterface):
    bl_idname = "TestSocketInt"
    bl_socket_idname = "TestSocket"
    
    def draw_color(self,context):
        return (0,.5,.8,1)
    
    def draw(self,context,layout):
        layout.prop(self,"hide_value")

class TestTree(NodeTree):
    bl_label = "Test Tree"
    bl_icon = "NODETREE"
    

classes = (TestTree,TestSocket,TestSocketInt)
cats = [NodeCategory('EXAMPLE','Example',items = [NodeItem('NodeGroupInput')])]

def register():
    from bpy.utils import register_class
    for cls in classes:
        register_class(cls)
    nodeitems_utils.register_node_categories('EXAMPLE_NODES', cats)
    
def unregister():
    from bpy.utils import unregister_class
    for cls in classes:
        unregister_class(cls)
    nodeitems_utils.unregister_node_categories('EXAMPLE_NODES')

if __name__ == "__main__":
    register()

2. Add a new "Test Tree".

3. Add a group input node.

4. Add "Example socket" input. Right here, how can this list be filtered?

Answer 1

You need to override valid_socket_type(idname) of class TestTree(NodeTree) https://docs.blender.org/api/master/bpy.types.NodeTree.html#bpy.types.NodeTree.valid_socket_type