make 'utoipa' an optional feature in 'utoipa-axum'

[woshilapin]

In the project I work on, we use utoipa to generate the OpenAPI file as a sub-command of the main application: it's not exposed anywhere in the webserver. But this sub-command is rarely modified. We mostly work on the web server part that don't need all the utoipa annotations, only the axum::Router part. Therefore, we pay the price of code generation of utoipa::ToSchema and utoipa::path on each and every compilation or rust-analyzer iteration, but we mostly need the axum::Router to be defined, not the entire OpenAPI schema.

Would it make sense to make utoipa a [feature] (enabled by default) of utoipa-axum? Is this a wild idea, or does it make sense?

I've started looking around for how to technically realize this kind of thing... and if I understand correctly, that would not be trivial to implement. As far as I can understand, the axum::Router is based on the implementation of utoipa::Path on the handlers, which means that disabling utoipa means losing the necessary metadata to build the router. So I guess we would need an intermediate representation for OpenApiRouter that doesn't depend on utoipa directly. I'm taking any idea, hint, warning, I might try to explore that.

And sorry if there was already a similar discussion/issue, I tried to find related topics but couldn't, for lack of good keywords ("optional", "feature"?).