Generate ISL from Smithy IDL

[mwfpope]

Smithy is a framework that allows you to write a service definition once and get generated Typescript, Go, OpenAPI etc. based on your service definition.

Being able to generate ISL from Smithy would allow someone to write a schema once as Smithy IDL and generate both ISL and corresponding POJOs (or equivalent structures in other languages).

This could also be a way of solving ion-schema-kotlin #146, albeit in a bit of a round-about way.

[mwfpope]

While researching something else, I found this comment in ion-schema-kotlin #35 where someone was asking for a flattened view of types that use inheritance and also some automatically generated documentation. Generating ISL from Smithy IDL could also solve this person's problem (again, in a slightly roundabout way) by taking advantage of Smithy's existing tools for generating documentation.

I've realized that what I envision as a solution to this feature request is not really an enhancement in this github project, but rather a separate project that would be a Smithy code generator targeting ISL. If this feature request is too off-topic for this github project, feel free to close this issue and let me know a better place to bring this up for discussion.

[pbcornell]

Hi Matthew, this is a fine location for your feature request at this time, and thank you for submitting it. I agree with your observations, and this sounds like a useful feature/tool.

It also appears that Smithy has some level of JSON Schema support (see smithy-jsonschema) although to what extent I haven't checked. Makes me wonder if there's a possibility of using ISL directly with Smithy, rather than requiring a conversion step...?