Add tryDecode and tryEncode to json

[rifkyputra]

json.decode will throw error when input is empty string.

Uncaught Error: FormatException: SyntaxError: Unexpected end of JSON input

here is the sample :

import 'dart:convert';

void main() {
  
  final foo = "";
  
  final list = json.decode(foo);
  
  print(list);
 
  
}

it would be nice to add json.tryDecode and json.tryEncode since json data can be from external source such as api or shared pref (in flutter).

[rifkyputra]

import 'dart:convert';

void main() {
  final content =' {"s": "hello"}';
  
  
  final foo = validJson.encode(content);
  print(foo);
  
  
  final bar= validJson.encode("");
  print(bar);
  
  final baz = validJson.encode("Not Valid Json");
  print(baz);
  
  
}


const ValidJson validJson = ValidJson();

class ValidJson {
  
  const ValidJson();
  
  String? encode(Object value,  {Object? Function(dynamic)? toEncodable}) {
    
    if (value is String) {
       try {
         json.decode(value) as Map;
         return value;
      } catch(e) {
        return null;
      }
    }
    
    
    final encoded = json.encode(value, toEncodable: toEncodable);
    
    try {
      json.decode(encoded) as Map;
    } catch(e) {
      print(e);
      return null;
    }
    
    
    return encoded;
    
  } 
}

[lrhn]

The argument against having json.tryDecode is that a valid decoding can also return null, so there would be no way to tell the difference between json.tryDecode("null") and json.tryDecode("arglebargle").

On the other hand, people decoding JSON usually know that they're expecting a list or map, and would treat a null as as an error anyway.