fix(ctl): fix formatting when printing messages without arguments (4.3)

Without passing an empty argument list to `emqx_ctl:print`, formatting
instructions like `~n` are being printed literally.

```
Ignore.~nJoin the cluster successfully.~nCluster status: #{running_nodes =>
                      ['emqx@emqx-0.int.thalesmg','emqx@emqx-1.int.thalesmg',
                       'emqx@emqx-2.int.thalesmg','emqx@emqx-3.int.thalesmg',
                       'emqx@emqx-4.int.thalesmg'],
                  stopped_nodes => []}
```

apps/emqx_auth_mnesia/test/emqx_acl_mnesia_SUITE.erl

@@ -302,7 +302,7 @@ t_start_stop_supervised(_Config) ->
 
 t_acl_cli(_Config) ->
     meck:new(emqx_ctl, [non_strict, passthrough]),
-    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg) end),
+    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg, []) end),
     meck:expect(emqx_ctl, print, fun(Msg, Arg) -> emqx_ctl:format(Msg, Arg) end),
     meck:expect(emqx_ctl, usage, fun(Usages) -> emqx_ctl:format_usage(Usages) end),
     meck:expect(emqx_ctl, usage, fun(Cmd, Descr) -> emqx_ctl:format_usage(Cmd, Descr) end),

apps/emqx_management/test/emqx_mgmt_SUITE.erl

@@ -158,9 +158,9 @@ t_clients_cmd(_) ->
     timer:sleep(300),
     emqx_mgmt_cli:clients(["list"]),
     ?assertMatch({match, _}, re:run(emqx_mgmt_cli:clients(["show", "client12"]), "client12")),
-    ?assertEqual("ok~n", emqx_mgmt_cli:clients(["kick", "client12"])),
+    ?assertEqual("ok\n", emqx_mgmt_cli:clients(["kick", "client12"])),
     timer:sleep(500),
-    ?assertEqual("ok~n", emqx_mgmt_cli:clients(["kick", "client12"])),
+    ?assertEqual("ok\n", emqx_mgmt_cli:clients(["kick", "client12"])),
     receive
         {'EXIT', T, _} ->
             ok
@@ -272,8 +272,8 @@ t_subscriptions_cmd(_) ->
     timer:sleep(300),
     [?assertMatch({match, _} , re:run(Result, "b/b/c"))
      || Result <- emqx_mgmt_cli:subscriptions(["show", <<"client">>])],
-    ?assertEqual(emqx_mgmt_cli:subscriptions(["add", "client", "b/b/c", "0"]), "ok~n"),
-    ?assertEqual(emqx_mgmt_cli:subscriptions(["del", "client", "b/b/c"]), "ok~n"),
+    ?assertEqual(emqx_mgmt_cli:subscriptions(["add", "client", "b/b/c", "0"]), "ok\n"),
+    ?assertEqual(emqx_mgmt_cli:subscriptions(["del", "client", "b/b/c"]), "ok\n"),
     unmock_print().
 
 t_listeners_cmd_old(_) ->
@@ -325,7 +325,7 @@ t_plugins_cmd(_) ->
       ),
     ?assertEqual(
        emqx_mgmt_cli:plugins(["unload", "emqx_management"]),
-       "Plugin emqx_management can not be unloaded.~n"
+       "Plugin emqx_management can not be unloaded.\n"
       ),
     unmock_print().
 
@@ -359,7 +359,7 @@ t_cli(_) ->
 mock_print() ->
     catch meck:unload(emqx_ctl),
     meck:new(emqx_ctl, [non_strict, passthrough]),
-    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg) end),
+    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg, []) end),
     meck:expect(emqx_ctl, print, fun(Msg, Arg) -> emqx_ctl:format(Msg, Arg) end),
     meck:expect(emqx_ctl, usage, fun(Usages) -> emqx_ctl:format_usage(Usages) end),
     meck:expect(emqx_ctl, usage, fun(Cmd, Descr) -> emqx_ctl:format_usage(Cmd, Descr) end).

apps/emqx_recon/test/emqx_recon_SUITE.erl

@@ -105,10 +105,9 @@ cli_usage(_) ->
 mock_print() ->
     catch meck:unload(emqx_ctl),
     meck:new(emqx_ctl, [non_strict, passthrough]),
-    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg) end),
+    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg, []) end),
     meck:expect(emqx_ctl, print, fun(Msg, Arg) -> emqx_ctl:format(Msg, Arg) end),
     meck:expect(emqx_ctl, usage, fun(Usages) -> emqx_ctl:format_usage(Usages) end).
 
 unmock_print() ->
     meck:unload().
-

apps/emqx_rule_engine/test/emqx_rule_engine_SUITE.erl

@@ -538,7 +538,7 @@ t_rules_cli(_Config) ->
     ?assertMatch({match, _}, re:run(RUpdate, "updated")),
 
     RDelete = emqx_rule_engine_cli:rules(["delete", RuleId]),
-    ?assertEqual("ok~n", RDelete),
+    ?assertEqual("ok\n", RDelete),
     %ct:pal("RDelete : ~p", [RDelete]),
     %ct:pal("table action params after deleted: ~p", [ets:tab2list(emqx_action_instance_params)]),
 
@@ -578,7 +578,7 @@ t_resources_cli(_Config) ->
     %ct:pal("RShow : ~p", [RShow]),
 
     RDelete = emqx_rule_engine_cli:resources(["delete", ResId]),
-    ?assertEqual("ok~n", RDelete),
+    ?assertEqual("ok\n", RDelete),
 
     RShow2 = emqx_rule_engine_cli:resources(["show", ResId]),
     ?assertMatch({match, _}, re:run(RShow2, "Cannot found")),
@@ -1387,7 +1387,7 @@ t_metrics1(_Config) ->
     ?assertEqual(0, emqx_rule_metrics:get_rules_passed(RuleId)),
     ?assertEqual(0, emqx_rule_metrics:get_rules_failed(RuleId)),
     ?assertEqual(0, emqx_rule_metrics:get_rules_exception(RuleId)),
-    ?assertEqual(0, emqx_rule_metrics:get_rules_no_result(RuleId)),   
+    ?assertEqual(0, emqx_rule_metrics:get_rules_no_result(RuleId)),
     {ok, Client} = emqtt:start_link([{username, <<"emqx">>}]),
     {ok, _} = emqtt:connect(Client),
     ct:sleep(200),
@@ -2711,7 +2711,7 @@ set_special_configs(_App) ->
 mock_print() ->
     catch meck:unload(emqx_ctl),
     meck:new(emqx_ctl, [non_strict, passthrough]),
-    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg) end),
+    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg, []) end),
     meck:expect(emqx_ctl, print, fun(Msg, Arg) -> emqx_ctl:format(Msg, Arg) end),
     meck:expect(emqx_ctl, usage, fun(Usages) -> emqx_ctl:format_usage(Usages) end),
     meck:expect(emqx_ctl, usage, fun(Cmd, Descr) -> emqx_ctl:format_usage(Cmd, Descr) end).
@@ -2763,4 +2763,3 @@ t_clear_resource(_) ->
 
 t_clear_action(_) ->
     error('TODO').
-

lib-ce/emqx_modules/test/emqx_modules_SUITE.erl

@@ -143,7 +143,7 @@ t_join_cluster(_) ->
 mock_print() ->
     catch meck:unload(emqx_ctl),
     meck:new(emqx_ctl, [non_strict, passthrough]),
-    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg) end),
+    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg, []) end),
     meck:expect(emqx_ctl, print, fun(Msg, Arg) -> emqx_ctl:format(Msg, Arg) end),
     meck:expect(emqx_ctl, usage, fun(Usages) -> emqx_ctl:format_usage(Usages) end),
     meck:expect(emqx_ctl, usage, fun(Cmd, Descr) -> emqx_ctl:format_usage(Cmd, Descr) end).

src/emqx_ctl.erl

@@ -43,8 +43,7 @@
         ]).
 
 %% Exports mainly for test cases
--export([ format/1
-        , format/2
+-export([ format/2
         , format_usage/1
         , format_usage/2
         ]).
@@ -137,7 +136,7 @@ help() ->
 
 -spec(print(io:format()) -> ok).
 print(Msg) ->
-    io:format("~s", [format(Msg)]).
+    io:format("~s", [format(Msg, [])]).
 
 -spec(print(io:format(), [term()]) -> ok).
 print(Format, Args) ->
@@ -151,10 +150,6 @@ usage(UsageList) ->
 usage(CmdParams, Desc) ->
     io:format(format_usage(CmdParams, Desc)).
 
--spec(format(io:format()) -> string()).
-format(Msg) ->
-    lists:flatten(io_lib:format("~s", [Msg])).
-
 -spec(format(io:format(), [term()]) -> string()).
 format(Format, Args) ->
     lists:flatten(io_lib:format(Format, Args)).

test/emqx_ctl_SUITE.erl

@@ -70,7 +70,7 @@ t_print(_) ->
     ok = emqx_ctl:print("~s", [<<"~!@#$%^&*()">>]),
     % - check the output of the usage
     mock_print(),
-    ?assertEqual("help~n", emqx_ctl:print("help~n")),
+    ?assertEqual("help\n", emqx_ctl:print("help~n")),
     ?assertEqual("help", emqx_ctl:print("~s", [help])),
     ?assertEqual("~!@#$%^&*()", emqx_ctl:print("~s", [<<"~!@#$%^&*()">>])),
     unmock_print().
@@ -110,7 +110,7 @@ mock_print() ->
     %% proxy usage/1,2 and print/1,2 to format_xx/1,2 funcs
     catch meck:unload(emqx_ctl),
     meck:new(emqx_ctl, [non_strict, passthrough]),
-    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg) end),
+    meck:expect(emqx_ctl, print, fun(Arg) -> emqx_ctl:format(Arg, []) end),
     meck:expect(emqx_ctl, print, fun(Msg, Arg) -> emqx_ctl:format(Msg, Arg) end),
     meck:expect(emqx_ctl, usage, fun(Usages) -> emqx_ctl:format_usage(Usages) end),
     meck:expect(emqx_ctl, usage, fun(CmdParams, CmdDescr) ->