Allow inline lists

Hi! I saw https://github.com/awslabs/smithy/blob/idl-2.0-rc-1/designs/inline-io.md and wondered if something similar could happen for lists:

instead of

structure User {
  names: Names
}

list Names { member: Name }

it would be possible to do

structure User {
  names: [Name]
}

(or similar) and a shape like Names could be implicitly assumed to exist without the spec author having to write it.

This is not only a syntactic convenience, it would also aid refactoring (fewer symbols to rename).

Thanks 😃

[mtdowling]

Yeah 😃. The Smithy core team is pretty divided on whether this would be a net positive too. Inline lists look great in docs and examples, but in practice we’d probably discourage their use at AWS since we want to add constraints to basically every list/set/map/string to make them bounded in some way, and we really don’t want teams to fall into the trap of repeating themselves.

If we do add something for inline list definitions, it would be in 2.1 or later since we’re working on wrapping up Smithy IDL 2.0.

[kubukoz]

Seems like quite a lot of work. Maybe it’s better to just bite the bullet and type the extra characters 😅

In the future it could be made easier with an editor code action (e.g. “create missing type” which would default to a list type based on some naming heuristics)