Proper / QuickCheck bounded recursive generator for JSON

proper_json.erl

-module(proper_json).

-export([json/0, json/1]).

json() ->
  ?SIZED(Size, json(Size)).


json(0) ->
  j_literal();
json(Size) ->
  ?LAZY(proper_types:frequency(
          [{60, j_literal()},
           {20, j_array(Size)},
           {20, j_object(Size)}])).

j_object(0) ->
  #{};
j_object(Size) ->
  ?LET(KV,
       proper_types:list({j_string(), json(Size div 2)}),
       maps:from_list(KV)).

j_array(0) ->
  [];
j_array(Size) ->
  proper_types:list(json(Size div 2)).

j_string() ->
  %% proper_unicode:utf8().
  ?LET(Str,
       proper_types:non_empty(chars()),
       list_to_binary(Str)).

j_literal() ->
    proper_types:oneof(
      [j_string(),
       proper_types:integer(),
       proper_types:float(),
       proper_types:boolean(),
       null]).

chars() ->
  proper_types:list(
    proper_types:oneof(lists:seq($a, $z) ++
                         lists:seq($A, $Z) ++
                         lists:seq($0, $9))).