DataField property to ignore field from equatable props

[xsahil03x]

Currently, we don't have any option or property to mark a DataField to be ignored from equatable props. We should add a property for the same.

[astralstriker]

suggest a name for the said property, I am struggling to find a good name :P

[xsahil03x]

shouldEquate maybe? @passsy any suggestions.

[passsy]

Instead of blindly adding this feature I'd like to see a real-world example where this is useful.

1. Immutable sealed classes should definitely not have a custom equals method. Every member counts.
2. Mutable classes should not have an equals method at all. See Avoid defining custom equality for mutable classes

And I've never seen a good example where a partially equals method implementation actually made sense. It might only be used for a special use case and might be better implemented using a custom comparison method, not the operator ==().

void main() {
  final itemA = Item("A");
  final itemB = Item("B")..added = false;
  final itemB2 = Item("B")..added = true;
  print(itemA == itemB); // false
  print(itemB == itemB2); // false
  print(itemA.customEquals(itemB)); // false
  print(itemB.customEquals(itemB2)); // true
}

class Item {
  Item(this.name);
  final String name;
  
  // mutable property
  bool added;
}

extension ItemEquality on Item {
  /// Only checks for the name 
  bool customEquals(dynamic other) => (other is Item) && name == other.name;
}

My recommendation: Add a property to skip generating the equals method at all. It could be useful for mutable super_enums. Users of such classes then could implement an extension for that type to implement their own equals method. (Sadly overriding operator ==() doesn't work with extensions).

[xsahil03x]

@passsy yes, makes sense to me.