Nodes: Show node description in Node add menu

Though no nodes have descriptions currently, this patch makes it
possible to add descriptions that display in the add menu, for
custom node systems and existing builtin nodes.

Differential Revision: https://developer.blender.org/D14963

release/scripts/startup/bl_operators/node.py

@@ -129,6 +129,15 @@ class NodeAddOperator:
 
         return result
 
+    @classmethod
+    def description(cls, context, properties):
+        nodetype = properties["type"]
+        bl_rna = bpy.types.Node.bl_rna_get_subclass(nodetype)
+        if bl_rna is not None:
+            return bl_rna.description
+        else:
+            return ""
+
 
 # Simple basic operator for adding a node
 class NODE_OT_add_node(NodeAddOperator, Operator):