DeepMerge Dart

deepmerge.dart

emptyTarget(val) {
  return val is List ? [] : {};
}

dynamic cloneUnlessOtherwiseSpecified(value) {
  print('$value');
  return isMergeableObject(value)
      ? deepmerge(emptyTarget(value), value)
      : value;
}

List defaultArrayMerge(List target, List source) {
  return [...target, ...source]
      .map((element) => cloneUnlessOtherwiseSpecified(element))
      .toList();
}

bool propertyIsOnObject(Map<dynamic, dynamic> object, dynamic property) {
  return object.containsKey(property);
}

// Protects from prototype poisoning and unexpected merging up the prototype chain.
bool propertyIsUnsafe(target, key) {
  return propertyIsOnObject(target, key); // Properties are safe to merge if they don't exist in the target yet
}

bool isMergeableObject(obj) {
  return obj != null && (obj is List || obj is Map);
}

Map<dynamic, dynamic> mergeObject(
    Map<dynamic, dynamic> target, Map<dynamic, dynamic> source) {
  Map<dynamic, dynamic> destination = {};

  if (isMergeableObject(target)) {
    for (final key in target.keys) {
      destination[key] = cloneUnlessOtherwiseSpecified(target[key]);
    }
  }

  for (final key in source.keys) {
    if (propertyIsUnsafe(target, key)) {
      continue;
    }
    
    print('T: $target S: $source');

    if (propertyIsOnObject(target, key) && isMergeableObject(source[key])) {
      destination[key] = deepmerge(target[key], source[key]);
    } else {
      destination[key] = cloneUnlessOtherwiseSpecified(source[key]);
    }
  }

  return destination;
}

deepmerge(dynamic target, dynamic source) {
  final isList = target is List && source is List;
  final isMap = target is Map && source is Map;
  if (isMap) {
    print(target);
    return mergeObject(target, source);
  } else if (isList) {
    print('lizf $target $source');
    return defaultArrayMerge(target, source);
  } else {
    return cloneUnlessOtherwiseSpecified(source);
  }
}

void main() {
  print('ciao');
  final Map<String, dynamic> a = {
    'zio': 1,
    'rotolo': 2,
    'pino': [4]
  };

  final Map<String, dynamic> b = {
    'zio': 'pane',
    'giovannni': 'pallini',
    'pino': [3]
  };

  final r = deepmerge(a, b);

  print('result: $r');
}