Make @lazy_property handlers read/write protected to avoid common newbie mistakes, like assigning obj.locks = []

CHANGELOG.md

@@ -95,6 +95,9 @@ Up requirements to Django 3.2+, Twisted 21+
 - Add validation question to default account creation.
 - Add `LOCALECHO` client option to add server-side echo for clients that does
   not support this (useful for getting a complete log).
+- Make `@lazy_property` decorator create read/delete-protected properties. This is
+  because it's used for handlers, and e.g. self.locks=[] is a common beginner mistake.
+
 
 
 ### Evennia 0.9.5 (2019-2020)

evennia/utils/utils.py

@@ -2064,7 +2064,8 @@ class lazy_property:
         ```
 
     Once initialized, the `AttributeHandler` will be available as a
-    property "attributes" on the object.
+    property "attributes" on the object. This is read-only since
+    this functionality is pretty much exclusively used by handlers.
 
     """
 
@@ -2085,6 +2086,24 @@ class lazy_property:
         obj.__dict__[self.__name__] = value
         return value
 
+    def __set__(self, obj, value):
+        """Protect against setting"""
+        handlername = self.__name__
+        raise AttributeError(
+            _("{obj}.{handlername} is a handler and can't be set directly. "
+              "To add values, use `{obj}.{handlername}.add()` instead.").format(
+                  obj=obj, handlername=handlername)
+        )
+
+    def __delete__(self, obj):
+        """Protect against deleting"""
+        handlername = self.__name__
+        raise AttributeError(
+            _("{obj}.{handlername} is a handler and can't be deleted directly. "
+              "To remove values, use `{obj}.{handlername}.remove()` instead.").format(
+                  obj=obj, handlername=handlername)
+        )
+
 
 _STRIP_ANSI = None
 _RE_CONTROL_CHAR = re.compile(