iolist_to_binary is usualy not the best choice for list values

[seriyps]

As discussed in the forum https://erlangforums.com/t/logstasher-is-erlang-logger-formatter-for-logstash/1026/2

Just applying term_to_binary to any list that happens to be a valid iolist is not always intuitive

The one trying to log smth like that:

Tags = ["foo", "bar", "baz"],
logger:info(#{label => something_happened, tags => Tags})

would rater expect it to be logged as

{"label": "something_happened", "tags": ["foo", "bar", "baz"]}

than

{"label": "something_happened", "tags": "foobarbaz"}

In our project we ended up with smth like

term_to_json([C | _] = List) when is_integer(C) ->
    case io_lib:char_list(S) of
      true ->
        unicode:characters_to_binary(List, utf8);  %% string() or specific form of unicode:chardata()
      false ->
        lists:map(fun term_to_json/1, List)  % JS array
    end;

---

Another issue is that calling iolist_to_binary is not guaranteed to succeed if it's guarded by io_lib:char_list:

> S = "привет", io_lib:char_list(S).       
true
> iolist_to_binary(S).
** exception error: bad argument
     in function  iolist_to_binary/1
        called as iolist_to_binary([1087,1088,1080,1074,1077,1090])
        *** argument 1: not an iodata term

unicode:characters_to_binary(S, utf8) might be a better choice.