refactor: use option to skip rendering as string

apps/emqx_message_transformation/src/emqx_message_transformation.erl

@@ -160,7 +160,14 @@ eval_operation(Operation, Transformation, Context) ->
 -spec eval_variform([binary(), ...], _, eval_context()) ->
     {ok, rendered_value()} | {error, term()}.
 eval_variform(K, V, Context) ->
-    case emqx_variform:render(V, Context) of
+    Opts =
+        case K of
+            [<<"payload">> | _] ->
+                #{eval_as_string => false};
+            _ ->
+                #{}
+        end,
+    case emqx_variform:render(V, Context, Opts) of
         {error, Reason} ->
             {error, Reason};
         {ok, Rendered} ->

apps/emqx_message_transformation/src/emqx_message_transformation_bif.erl

@@ -28,7 +28,7 @@ json_encode(X) ->
 json_decode(JSON) ->
     case emqx_utils_json:safe_decode(JSON, [return_maps]) of
         {ok, X} ->
-            emqx_variform:skip_stringification(X);
+            X;
         {error, Reason} ->
             throw(#{reason => json_decode_failure, detail => Reason})
     end.

apps/emqx_utils/src/emqx_variform.erl

@@ -31,7 +31,6 @@
 
 -export([render/2, render/3]).
 -export([compile/1, decompile/1]).
--export([skip_stringification/1]).
 
 -export_type([compiled/0]).
 
@@ -44,7 +43,6 @@
 ).
 
 -define(IS_EMPTY(X), (X =:= <<>> orelse X =:= "" orelse X =:= undefined)).
--define(SKIP_STRINGIFICATION, {?MODULE, '__skip_stringification__'}).
 
 %% @doc Render a variform expression with bindings.
 %% A variform expression is a template string which supports variable substitution
@@ -71,7 +69,7 @@ render(Expression, Bindings) ->
     render(Expression, Bindings, #{}).
 
 render(#{form := Form}, Bindings, Opts) ->
-    eval_as_string(Form, Bindings, Opts);
+    eval_render(Form, Bindings, Opts);
 render(Expression, Bindings, Opts) ->
     case compile(Expression) of
         {ok, Compiled} ->
@@ -80,9 +78,16 @@ render(Expression, Bindings, Opts) ->
             {error, Reason}
     end.
 
-eval_as_string(Expr, Bindings, _Opts) ->
+eval_render(Expr, Bindings, Opts) ->
+    EvalAsStr = maps:get(eval_as_string, Opts, true),
     try
-        {ok, return_str(eval(Expr, Bindings, #{}))}
+        Result = eval(Expr, Bindings, #{}),
+        case EvalAsStr of
+            true ->
+                {ok, return_str(Result)};
+            false ->
+                {ok, Result}
+        end
     catch
         throw:Reason ->
             {error, Reason};
@@ -95,9 +100,6 @@ return_str(Str) when is_binary(Str) -> Str;
 return_str(Num) when is_integer(Num) -> integer_to_binary(Num);
 return_str(Num) when is_float(Num) -> float_to_binary(Num, [{decimals, 10}, compact]);
 return_str(Atom) when is_atom(Atom) -> atom_to_binary(Atom, utf8);
-%% For usage by other modules (e.g.: message transformation)
-return_str({?SKIP_STRINGIFICATION, X}) ->
-    X;
 return_str(Other) ->
     throw(#{
         reason => bad_return,
@@ -105,9 +107,6 @@ return_str(Other) ->
         got => Other
     }).
 
-skip_stringification(X) ->
-    {?SKIP_STRINGIFICATION, X}.
-
 %% @doc Compile varifom expression.
 -spec compile(string() | binary() | compiled()) -> {ok, compiled()} | {error, any()}.
 compile(#{form := _} = Compiled) ->