rabbit_vhost: Emit vhost_deleted only if the vhost was actually deleted

This was the case before the reorganize of the code made in #6430 and
therefore a regression in the mentionned pull request. This patch
restores the behavior.

Note that this is already like that for internal users. Thus, the
behavior and `rabbit_db_*` are consistent.

Author: dumbbell

deps/rabbit/src/rabbit_db_vhost.erl

@@ -297,11 +297,12 @@ with_fun_in_mnesia_tx(VHostName, TxFun)
 %% delete().
 %% -------------------------------------------------------------------
 
--spec delete(VHostName) -> ok when
-      VHostName :: vhost:name().
-%% @doc Deletes a virtual host record.
+-spec delete(VHostName) -> Existed when
+      VHostName :: vhost:name(),
+      Existed :: boolean().
+%% @doc Deletes a virtual host record from the database.
 %%
-%% @returns `ok', even if the record didn't exist before. It throws an
+%% @returns a boolean indicating if the vhost existed or not. It throws an
 %% exception if the transaction fails.
 %%
 %% @private
@@ -315,5 +316,6 @@ delete_in_mnesia(VHostName) ->
       fun() -> delete_in_mnesia_tx(VHostName) end).
 
 delete_in_mnesia_tx(VHostName) ->
+    Existed = mnesia:wread({?MNESIA_TABLE, VHostName}) =/= [],
     mnesia:delete({?MNESIA_TABLE, VHostName}),
-    ok.
+    Existed.

deps/rabbit/src/rabbit_vhost.erl

@@ -286,9 +286,15 @@ delete(VHost, ActingUser) ->
     _ = rabbit_runtime_parameters:clear_vhost(VHost, ActingUser),
     _ = [rabbit_policy:delete(VHost, proplists:get_value(name, Info), ActingUser)
          || Info <- rabbit_policy:list(VHost)],
-    ok = rabbit_db_vhost:delete(VHost),
-    ok = rabbit_event:notify(vhost_deleted, [{name, VHost},
-                                             {user_who_performed_action, ActingUser}]),
+    case rabbit_db_vhost:delete(VHost) of
+        true ->
+            ok = rabbit_event:notify(
+                   vhost_deleted,
+                   [{name, VHost},
+                    {user_who_performed_action, ActingUser}]);
+        false ->
+            ok
+    end,
     %% After vhost was deleted from the database, we try to stop vhost
     %% supervisors on all the nodes.
     rabbit_vhost_sup_sup:delete_on_all_nodes(VHost),