refactor: move version prefix string detection to a static fun

this is to make dialyzer happy

apps/emqx/src/emqx_release.erl

@@ -18,6 +18,7 @@
 
 -export([
     edition/0,
+    edition_vsn_prefix/0,
     edition_longstr/0,
     description/0,
     version/0
@@ -45,11 +46,11 @@ description() ->
 -spec edition() -> ce | ee.
 -ifdef(EMQX_RELEASE_EDITION).
 edition() -> ?EMQX_RELEASE_EDITION.
-
+edition_vsn_prefix() -> "e".
 edition_longstr() -> <<"Enterprise">>.
 -else.
 edition() -> ce.
-
+edition_vsn_prefix() -> "v".
 edition_longstr() -> <<"Opensource">>.
 -endif.
 

apps/emqx_machine/src/emqx_restricted_shell.erl

@@ -45,11 +45,7 @@ set_prompt_func() ->
 prompt_func(PropList) ->
     Line = proplists:get_value(history, PropList, 1),
     Version = emqx_release:version(),
-    Prefix =
-        case emqx_release:edition() of
-            ce -> "v";
-            ee -> "e"
-        end,
+    Prefix = emqx_release:edition_vsn_prefix(),
     case is_alive() of
         true -> io_lib:format(<<"~ts~ts(~s)~w> ">>, [Prefix, Version, node(), Line]);
         false -> io_lib:format(<<"~ts~ts ~w> ">>, [Prefix, Version, Line])