object function

Map<String, dynamic>? object(Map<String, dynamic> json, String key, String path)

Reads an optional sub-object. Absent reads as null; present but not an object throws.

This is deliberately stricter than opt. opt's licence covers a scalar widening — an older client reading a field the server changed the shape of. A whole container arriving as a scalar is a server bug, and reading it as absent turns it into a silently empty card or a deny-all permission set.

Implementation

Map<String, dynamic>? object(
  Map<String, dynamic> json,
  String key,
  String path,
) {
  final value = json[key];
  if (value == null) return null;
  if (value is! Map<String, dynamic>) {
    throw SchemaFormatException(
      _join(path, key),
      'expected object, got ${value.runtimeType}',
    );
  }
  return value;
}