add rebar.config.script for checking support maps and binary_to_{integer,float}/1

rebar.config

@@ -1,7 +1,5 @@
 {erl_opts, [
   % uncomment to always decode to maps
   % {d, maps_always},
-  {platform_define, "R14|R15", 'no_binary_to_whatever'},
-  {platform_define, "^((?!R1[456]).)*$", 'maps_support'}
 ]}.
 {edoc_opts, [{preprocess, true}]}.

rebar.config.script

@@ -0,0 +1,11 @@
+Def0 = case erlang:is_builtin(erlang, binary_to_integer, 1) andalso
+            erlang:is_builtin(erlang, binary_to_float, 1) of
+           true -> [];
+           false -> [{d, no_binary_to_whatever}]
+       end,
+Defs = case erlang:is_builtin(erlang, is_map, 1) of
+           true -> [{d, maps_support}|Def0];
+           false -> Def0
+       end,
+lists:keystore(erl_opts, 1, CONFIG,
+               {erl_opts, proplists:get_value(erl_opts, CONFIG, []) ++ Defs}).

src/jsx_decoder.erl

@@ -1010,8 +1010,7 @@ finish_number(Rest, Handler, Acc, Stack, Config) ->
 -ifndef(no_binary_to_whatever).
 format_number({integer, Acc}) -> {integer, binary_to_integer(Acc)};
 format_number({float, Acc}) -> {float, binary_to_float(Acc)}.
--endif.
+-else.
--ifdef(no_binary_to_whatever).
 format_number({integer, Acc}) -> {integer, list_to_integer(unicode:characters_to_list(Acc))};
 format_number({float, Acc}) -> {float, list_to_float(unicode:characters_to_list(Acc))}.
 -endif.