Enrich ModelDiff with a data structure describing shape differences

[miguel-vila]

Hey, in order to debug something in our logic, we had to kind of replicate the logic in Shape.equals (and in the subclasses). We are using ModelDiff, which provides with some basic diff information, but we needed to debug things a bit more. What we ended up doing was partially replicating Shape.equals but returning a data structure that would tell us what was the reason why the shapes are not considered equal.

For example, if the reason shape1.equals(shape2) returns false is a trait addition and a trait modification, then we would return (in Scala) something like List(Diffs.TraitsChanged(removed=List.empty, added = List(Trait(shapeId= ..., value = ...)), modified = List(TraitModified(valueBefore = ..., valueAfter = ...)))) .

We were wondering if Smithy could have this logic instead, as we don’t want to risk replicating and diverging from this. I think this could be a new field in ChangedShape describing the difference. Let us know what you think