Avoid yield-command crossover problems. Add .retain_instance ability for Command class for implementing state execution.

CHANGELOG.md

@@ -76,6 +76,8 @@ Up requirements to Django 3.2+
   pathfinding. Controlled outside of the game via custom evennia launcher command.
 - `Script.delete` has new kwarg `stop_task=True`, that can be used to avoid
   infinite recursion when wanting to set up Script to delete-on-stop.
+- Command executions now done on copies to make sure `yield` don't cause crossovers. Add
+  `Command.retain_instance` flag for reusing the same command instance.
 
 ### Evennia 0.9.5 (2019-2020)
 

evennia/commands/cmdhandler.py

@@ -738,6 +738,10 @@ def cmdhandler(
                             sysarg += _(' Type "help" for help.')
                     raise ExecSystemCommand(syscmd, sysarg)
 
+            if not cmd.retain_instance:
+                # making a copy allows multiple users to share the command also when yield is used
+                cmd = copy(cmd)
+
             # A normal command.
             ret = yield _run_command(cmd, cmdname, args, raw_cmdname, cmdset, session, account)
             returnValue(ret)

evennia/commands/command.py

@@ -84,6 +84,9 @@ def _init_command(cls, **kwargs):
         cls.is_exit = False
     if not hasattr(cls, "help_category"):
         cls.help_category = "general"
+    if not hasattr(cls, "retain_instance"):
+        cls.retain_instance = False
+
     # make sure to pick up the parent's docstring if the child class is
     # missing one (important for auto-help)
     if cls.__doc__ is None:
@@ -189,6 +192,11 @@ class Command(metaclass=CommandMeta):
     # whether self.msg sends to all sessions of a related account/object (default
     # is to only send to the session sending the command).
     msg_all_sessions = settings.COMMAND_DEFAULT_MSG_ALL_SESSIONS
+    # whether the exact command instance should be retained between command calls.
+    # By default it's False; this allows for retaining state and saves some CPU, but
+    # can cause cross-talk between users if multiple users access the same command
+    # (especially if the command is using yield)
+    retain_instance = False
 
     # auto-set (by Evennia on command instantiation) are:
     #   obj - which object this command is defined on

evennia/utils/evmenu.py

@@ -1540,7 +1540,8 @@ class CmdGetInput(Command):
             getinput = caller.ndb._getinput
             if not getinput and hasattr(caller, "account"):
                 getinput = caller.account.ndb._getinput
-                caller = caller.account
+                if getinput:
+                    caller = caller.account
             callback = getinput._callback
 
             caller.ndb._getinput._session = self.session
@@ -1642,7 +1643,7 @@ def get_input(caller, prompt, callback, session=None, *args, **kwargs):
     caller.ndb._getinput._session = session
     caller.ndb._getinput._args = args
     caller.ndb._getinput._kwargs = kwargs
-    caller.cmdset.add(InputCmdSet)
+    caller.cmdset.add(InputCmdSet, persistent=False)
     caller.msg(prompt, session=session)