API semantics for deep nested evolve calls

When trying to evolve a frozen object at a deep level, there is a lot of boilerplate, e.g.,:

foo = attr.evolve(
   foo,
   bar=attr.evolve(
      foo.bar,
      baz=attr.evolve(
         foo.bar.baz,
         qux='whew!'
       )
   )
)

Scala has a similar problem, being that immutable data classes is a normal thing in that language. There is a Scala library developed helped to solve that problem: https://www.optics.dev/Monocle/

Maybe it would be useful to have those sort of semantics for updating frozen attr objects,e.g.:

foo = attr.focus(foo, Foo.bar.baz.qux).modify('yay!')

Any thoughts?

Start by reviewing the existing attr.evolve API and the nested frozen-object examples in the issue; no file or test entry point is named. Read the linked Monocle project for comparison, then define the proposed focus and modify semantics, supported paths, and acceptance criteria before assessing implementation scope.