In @desc command, validate rhs based on = sign present in orig args. Default MUX parsing assigns None to rhs if there is nothing on the right of the = sign.

evennia/commands/default/building.py

@@ -589,12 +589,12 @@ class CmdDesc(COMMAND_DEFAULT_CLASS):
             self.edit_handler()
             return
 
-        if self.rhs:
+        if '=' in self.args:
             # We have an =
             obj = caller.search(self.lhs)
             if not obj:
                 return
-            desc = self.rhs
+            desc = self.rhs or ''
         else:
             obj = caller.location or self.msg("|rYou can't describe oblivion.|n")
             if not obj:

evennia/commands/default/tests.py

@@ -264,6 +264,9 @@ class TestBuilding(CommandTest):
         self.call(building.CmdDesc(), "Obj2=TestDesc", "The description was set on Obj2(#5).")
 
     def test_empty_desc(self):
+        """
+        empty desc sets desc as ''
+        """
         o2d = self.obj2.db.desc
         r1d = self.room1.db.desc
         self.call(building.CmdDesc(), "Obj2=", "The description was set on Obj2(#5).")
@@ -271,6 +274,7 @@ class TestBuilding(CommandTest):
         assert self.room1.db.desc == r1d
 
     def test_desc_default_to_room(self):
+        """no rhs changes room's desc"""
         o2d = self.obj2.db.desc
         r1d = self.room1.db.desc
         self.call(building.CmdDesc(), "Obj2", "The description was set on Room(#1).")