Test Blender PYthon Nodes

nodes.py

bl_info = {
    'name': 'Node Test',
    'category': 'User',
    'author': 'Julian Jarecki',
    'blender': (2, 79, 0),
    # 'location': 'File > Export',
    'description': "Test custom Nodes and sockets",
}

import bpy

class MyNT(bpy.types.NodeTree):
    """ This operator is only visible when Cycles is the selected render engine"""
    bl_idname = "test_TNT"
    bl_label = "Test Node Tree"
    bl_icon = "QUESTION"
    
    new_links = []
    
    def update(self):
        for link in self.new_links:
            print("New link:", link, 
                  "from socket:", link.from_socket.bl_idname, 
                  "to socket:", link.to_socket.bl_idname)
            
            # if the socket type strings aren't equal, delete the link
            if link.from_socket.bl_idname != link.to_socket.bl_idname:
                self.links.remove(link)
                print("Types didn't match, deleted link")
        
        # We have checked all new links, clear and wait for the next update
        self.new_links.clear()
        

class Sock:
    def draw(self, context, layout, node, x):
        layout.label(self.name)

    def draw_color(self, context, node):
        return (1, 1, 1, 1)

class SockA(bpy.types.NodeSocket, Sock):
    bl_idname = "test_sockA"
    bl_label = "Socket A"

class SockB(bpy.types.NodeSocket, Sock):
    bl_idname = "test_sockB"
    bl_label = "Socket B"

class TestNode(bpy.types.Node):
    bl_idname = "test_node"
    bl_label = "Test Node"

    def init(self, context):
        self.inputs.new("test_sockA", "in A")
        self.outputs.new("test_sockA", "out A")
        self.inputs.new("test_sockB", "in B")
        self.outputs.new("test_sockB", "out B")
    
    def insert_link(self, link):
        # Note that this function is called BEFORE the new link is inserted into the node tree
        # So you can't delete the link in this function!
        print("a link was created (Node %s)" % self.name)
        node_tree = self.id_data
        if link in node_tree.new_links:
            print("link already flagged as new")
        else:
            node_tree.new_links.append(link)

def insertNode(layout, type, text, settings = {}, icon = "NONE"):
    operator = layout.operator("node.add_node", text = text, icon = icon)
    operator.type = type
    operator.use_transform = True
    for name, value in settings.items():
        item = operator.settings.add()
        item.name = name
        item.value = value
    return operator

def drawMenu(self, context):
    layout = self.layout
    layout.operator_context = "INVOKE_DEFAULT"
    insertNode(layout, "test_node", "Test Node")

types = [MyNT,SockA,SockB,TestNode]

def register():
    bpy.types.NODE_MT_add.append(drawMenu)
    for t in types:
        bpy.utils.register_class(t)


def unregister():
    bpy.types.NODE_MT_add.remove(drawMenu)
    for t in types:
        bpy.utils.unregister_class(t)