deserialize method

@override String? deserialize(DartType targetType, String expression, TypeHelperContext context, bool defaultProvided,)

Returns Dart code that deserializes an expression representing a JSON literal to into targetType.

If targetType is not supported, returns null.

Let's say you want to deserialize a class Foo by taking an int stored in a JSON literal and calling the Foo.fromInt constructor.

Treating expression as a opaque Dart expression representing a JSON literal, the deserialize implementation could be a simple as:

String deserialize(DartType targetType, String expression) =>
  "new Foo.fromInt($expression)";
```.

Note that [targetType] is not used here. If you wanted to support many
types of [targetType] you could write:

```dart
String deserialize(DartType targetType, String expression) =>
  "new ${targetType.name}.fromInt($expression)";
```.

Implementation

@override
String? deserialize(
  DartType targetType,
  String expression,
  TypeHelperContext context,
  bool defaultProvided,
) {
  if (!(coreIterableTypeChecker.isExactlyType(targetType) ||
      _coreListChecker.isExactlyType(targetType) ||
      _coreSetChecker.isExactlyType(targetType))) {
    return null;
  }

  final iterableGenericType = coreIterableGenericType(targetType);

  final itemSubVal = context.deserialize(iterableGenericType, closureArg)!;

  var output = '$expression as List<dynamic>';

  final targetTypeIsNullable = defaultProvided || targetType.isNullableType;

  if (targetTypeIsNullable) {
    output += '?';
  }

  // If `itemSubVal` is the same and it's not a Set, then we don't need to do
  // anything fancy
  if (closureArg == itemSubVal &&
      !_coreSetChecker.isExactlyType(targetType)) {
    return output;
  }

  output = '($output)';

  var optionalQuestion = targetTypeIsNullable ? '?' : '';

  if (closureArg != itemSubVal) {
    final lambda = LambdaResult.process(itemSubVal);
    output += '$optionalQuestion.map($lambda)';
    // No need to include the optional question below – it was used here!
    optionalQuestion = '';
  }

  if (_coreListChecker.isExactlyType(targetType)) {
    output += '$optionalQuestion.toList()';
  } else if (_coreSetChecker.isExactlyType(targetType)) {
    output += '$optionalQuestion.toSet()';
  }

  return output;
}