Json exception message on parse invalid Json string throws onRange error

[NesterovMaxim]

When I tried to parse following invalid Json string

string bad_request_nothing = `{"content": "123"`;

my program has crashed with message

core.exception.RangeError at vibe.data.json(864): Range violation
0x00500CA0 in onRangeError
...

When I check out the string in data/json.d I recognized following line with issue

enforceJson(!range.empty && (range.front == ',' || range.front == '}'), "Expected '}' or ',' - got '"~range[0]~"'.");

It checks range on empty and throws error message with data from empty range simultaneously.

I can suggest the following solution:

enforceJson(!range.empty && (range.front == ',' || range.front == '}'), "Expected '}' or ',' - got "~(range.empty?"nothing.":"'"~range[0]~"'."));

and check it by following unittests

import vibe.vibe;
import vibe.data.json : parseJsonString;

unittest
{
  string bad_request_nothing = `{"content": "123"`;
  try
  {
    Json request = parseJsonString(bad_request_nothing);
  }
  catch(JSONException e)
  {
    enforce(e.msg == "JSON format error at byte 17: Expected '}' or ',' - got nothing.");
  }
}

unittest
{
  string bad_request_k = `{"content": "123"k`;
  try
  {
    Json request = parseJsonString(bad_request_k);
  }
  catch(JSONException e)
  {
    enforce(e.msg == "JSON format error at byte 17: Expected '}' or ',' - got 'k'.");
  }
}