Setting attribute is not the same as setting the property. E. g. in Polymer 1.x there is attribute deserialization.
I think the element itself should catch property setting and only reflect it to attribute if necessary (in Polymer 1.x, this is configured via reflectToAttribute: true).
If you really need setting attribute, you should make this stuff opt-in and disabled by default for compatibility.
Setting attribute is not the same as setting the property. E. g. in Polymer 1.x there is attribute deserialization. I think the element itself should catch property setting and only reflect it to attribute if necessary (in Polymer 1.x, this is configured via
reflectToAttribute: true
). If you really need setting attribute, you should make this stuff opt-in and disabled by default for compatibility.