mergeMaps function

Map<String, Object> mergeMaps(Map<String, Object> base, Map<String, Object> modification)

Recursively merges modification into base.

In other words, whenever there is a conflict over the value of a key path, modification's value for that key path is selected.

Implementation

Map<String, Object> mergeMaps(
  Map<String, Object> base,
  Map<String, Object> modification,
) {
  final Map<String, Object> result = <String, Object>{};
  for (final MapEntry<String, Object> entry in modification.entries) {
    if (base.containsKey(entry.key)) {
      final Object entryValue = entry.value;
      if (entryValue is Map<String, Object>) {
        assert(base[entry.key] is Map<String, Object>);
        result[entry.key] =
            mergeMaps((base[entry.key] as Map<String, Object>?)!, entryValue);
      } else {
        result[entry.key] = entry.value;
      }
    } else {
      result[entry.key] = entry.value;
    }
  }
  for (final MapEntry<String, Object> entry in base.entries) {
    if (!result.containsKey(entry.key)) {
      result[entry.key] = entry.value;
    }
  }
  return result;
}