add sphinx api reference note that menu's layout.operator_context defaults to EXEC_REGION_WIN rather then INVOKE_DEFAULT.

doc/python_api/examples/bpy.types.Menu.py

@@ -10,6 +10,12 @@ convention for menus.
 .. note::
 
    Menu subclasses must be registered before referencing them from blender.
+
+.. note::
+   Menu's have their :class:`Layout.operator_context` initialized as
+   'EXEC_REGION_WIN' rather then 'INVOKE_DEFAULT', so if the operator context
+   needs to initialize inputs from the :class:`Operator.invoke` function
+   then this needs to be explicitly set.
 """
 import bpy
 

doc/python_api/examples/bpy.types.Operator.2.py

@@ -39,6 +39,7 @@ class ExportSomeData(bpy.types.Operator):
 
 # Only needed if you want to add into a dynamic menu
 def menu_func(self, context):
+    self.layout.operator_context = 'INVOKE_DEFAULT'
     self.layout.operator(ExportSomeData.bl_idname, text="Text Export Operator")
 
 # Register and add to the file selector