Minimalist equatable implementation that does not use third-party dependencies.

equatable.dart

abstract base class Equatable {
  const Equatable();

  List<Object?> get props;

  @override
  bool operator ==(Object other) {
    return identical(this, other) ||
        other is Equatable &&
            runtimeType == other.runtimeType &&
            _iterableEquals(props, other.props);
  }

  @override
  int get hashCode => runtimeType.hashCode ^ _mapPropsToHashCode(props);

  @override
  String toString() => _mapPropsToString(runtimeType, props);

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  int _mapPropsToHashCode(Iterable<Object?>? props) =>
      _finish(props == null ? 0 : props.fold(0, _combine));

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  bool _iterableEquals(Iterable<Object?> a, Iterable<Object?> b) {
    assert(
      a is! Set && b is! Set,
      "iterableEquals doesn't support Sets. Use setEquals instead.",
    );
    if (identical(a, b)) {
      return true;
    }

    if (a.length != b.length) {
      return false;
    }

    for (var i = 0; i < a.length; i++) {
      if (!_objectsEquals(a.elementAt(i), b.elementAt(i))) {
        return false;
      }
    }

    return true;
  }

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  bool _numEquals(num a, num b) => a == b;

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  bool _setEquals(Set<Object?> a, Set<Object?> b) {
    if (identical(a, b)) {
      return true;
    }

    if (a.length != b.length) {
      return false;
    }

    for (final element in a) {
      if (!b.any((e) => _objectsEquals(element, e))) {
        return false;
      }
    }

    return true;
  }

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  bool _mapEquals(Map<Object?, Object?> a, Map<Object?, Object?> b) {
    if (identical(a, b)) {
      return true;
    }

    if (a.length != b.length) {
      return false;
    }

    for (final key in a.keys) {
      if (!_objectsEquals(a[key], b[key])) {
        return false;
      }
    }

    return true;
  }

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  bool _objectsEquals(Object? a, Object? b) {
    if (identical(a, b)) {
      return true;
    }

    if (a is num && b is num) {
      return _numEquals(a, b);
    } else if (_isEquatable(a) && _isEquatable(b)) {
      return a == b;
    } else if (a is Set && b is Set) {
      return _setEquals(a, b);
    } else if (a is Iterable && b is Iterable) {
      return _iterableEquals(a, b);
    } else if (a is Map && b is Map) {
      return _mapEquals(a, b);
    } else if (a?.runtimeType != b?.runtimeType) {
      return false;
    } else if (a != b) {
      return false;
    }

    return true;
  }

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  bool _isEquatable(Object? object) => object is Equatable;

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  int _combine(int hash, Object? object) {
    if (object is Map) {
      object.keys
          .sorted((Object? a, Object? b) => a.hashCode - b.hashCode)
          .forEach((Object? key) {
            hash = hash ^ _combine(hash, [key, (object! as Map)[key]]);
          });
      return hash;
    }
    if (object is Set) {
      object = object.sorted((Object? a, Object? b) => a.hashCode - b.hashCode);
    }

    if (object is Iterable) {
      for (final value in object) {
        hash = hash ^ _combine(hash, value);
      }
      return hash ^ object.length;
    }

    hash = 0x1fffffff & (hash + object.hashCode);
    hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
    return hash ^ (hash >> 6);
  }

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  int _finish(int hash) {
    hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
    hash = hash ^ (hash >> 11);
    return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
  }

  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  String _mapPropsToString(Type runtimeType, List<Object?> props) =>
      '$runtimeType(${props.map((prop) => prop.toString()).join(', ')})';
}

extension _IterableExtension<T> on Iterable<T> {
  @pragma('vm:prefer-inline')
  @pragma('dart2js:tryInline')
  List<T> sorted(Comparator<T> compare) => [...this]..sort(compare);
}