fix(plugins): fix relative positioning

apps/emqx_plugins/src/emqx_plugins.erl

@@ -139,7 +139,7 @@ ensure_state(NameVsn, Position, State) ->
             Item = #{ name_vsn => NameVsn
                     , enable => State
                     },
-            ensure_configured(Item, Position);
+            tryit("ensure_state", fun() -> ensure_configured(Item, Position) end);
         {error, Reason} ->
             {error, Reason}
     end.
@@ -150,13 +150,18 @@ ensure_configured(#{name_vsn := NameVsn} = Item, Position) ->
     {Front, Rear} = lists:splitwith(SplitFun, Configured),
     NewConfigured =
         case Rear of
-            [_ | More] -> Front ++ [Item | More];
-            [] -> add_new_configured(Configured, Position, Item)
+            [_ | More] when Position =:= no_move ->
+                Front ++ [Item | More];
+            [_ | More] ->
+                add_new_configured(Front ++ More, Position, Item);
+            [] ->
+                add_new_configured(Configured, Position, Item)
         end,
     ok = put_configured(NewConfigured).
 
 add_new_configured(Configured, no_move, Item) ->
-    Configured ++ [Item];
+    %% default to rear
+    add_new_configured(Configured, rear, Item);
 add_new_configured(Configured, front, Item) ->
     [Item | Configured];
 add_new_configured(Configured, rear, Item) ->
@@ -164,6 +169,11 @@ add_new_configured(Configured, rear, Item) ->
 add_new_configured(Configured, {before, NameVsn}, Item) ->
     SplitFun = fun(#{name_vsn := Nv}) -> bin(Nv) =/= bin(NameVsn) end,
     {Front, Rear} = lists:splitwith(SplitFun, Configured),
+    Rear =:= [] andalso
+        throw(#{error => "position_anchor_plugin_not_configured",
+                hint => "maybe_install_and_configure",
+                name_vsn => NameVsn
+               }),
     Front ++ [Item | Rear].
 
 %% @doc Delete the package file.

apps/emqx_plugins/test/emqx_plugins_SUITE.erl

@@ -149,7 +149,7 @@ t_start_restart_and_stop(Config) ->
     assert_app_running(emqx_plugin_template, true),
 
     %% fake enable bar-2
-    ok = emqx_plugins:ensure_state(Bar2, reat, true),
+    ok = emqx_plugins:ensure_state(Bar2, rear, true),
     %% should cause an error
     ?assertError(#{function := _, errors := [_ | _]},
                  emqx_plugins:ensure_started()),

apps/emqx_plugins/test/emqx_plugins_tests.erl

@@ -31,7 +31,9 @@ test_ensure_configured() ->
     emqx_plugins:ensure_configured(P1, front),
     emqx_plugins:ensure_configured(P2, {before, <<"p-1">>}),
     emqx_plugins:ensure_configured(P3, {before, <<"p-1">>}),
-    ?assertEqual([P2, P3, P1], emqx_plugins:configured()).
+    ?assertEqual([P2, P3, P1], emqx_plugins:configured()),
+    ?assertThrow(#{error := "position_anchor_plugin_not_configured"},
+                 emqx_plugins:ensure_configured(P3, {before, <<"unknown-x">>})).
 
 read_plugin_test() ->
     with_rand_install_dir(