[RFC] Introducing MLIR Operation Properties

I think you can frame this more generally than « observability »: this is touching on introspection in general.
That said introspection of attributes and types has always been intrinsically limited: they are opaque structures defined by dialects.
Still we’re removing at least the ability to query the entries in a dictionary.

There isn’t any listener for modifying attributes at the moment, but properties will make it impossible to implement [RFC] Introduce the concept of IR listeners in MLIR comprehensively.