#[derive(CustomResource)] path dependencies

[semtexzv]

Current implementation of custom derive has a bunch or implicit assumptions about outer environment, which requires user to import crates under specific names.

I like to rename serde_json and k8s_openapi to json and k8s respectively, and It's impossible to do so currently
Changing the paths in the macro output to use undocumented re-exports from kube crate would solve this.

[clux]

Oh, interesting. You mean like having the macro generate code that depends on something like:

use kube_derive::serde_json::Deserialize;

Would that work? I don't want kube_derive to depend explicitly on kube, but that probably wasn't what you meant.

[semtexzv]

Yeah, could be. Goal is to reduce number of dependencies on external state in the custom derive.

//edit: I don't know whether you can import regular items from proc-macro crate.

[clux]

Revisiting this. Having dug into this more, turns out there's an open issue in rust-lang about this being hard: rust-lang/rust#54363
Serde has a similar issue.

Practically, we would need some way to refer to the up to three runtime dependencies kube-derive has:

• serde_json (needed in both codegen and generated code)
• schemars (optional, only needed in runtime code, user needs to select feature flags)
• k8s_openapi (needed only in runtime code, user needs to select feature flags)

As per the PR, I don't want to re-export these from kube, because kube-derive is actually fine as a stand-alone crate (schemars is only needed there). Strangely, the dependency tree is actually more natural this way around (kube re-exports kube-derive).

If it was possible for kube-derive to re-export these three with non-default features by itself, and then have users progressively enhance them with their own feature selection (because we can only have one version of a given package), then I would be in favour of it.

Unfortunately, proc_macro crates do not support this:

error: `proc-macro` crate types currently cannot export any items other than functions tagged with `#[proc_macro]`, `#[proc_macro_derive]`, or `#[proc_macro_attribute]`
   --> /home/clux/repos/kube-rs/kube-derive/src/lib.rs:209:1
    |
209 | pub use serde_json;
    | ^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error

Thus, I am going to close this for now. Unless there's movement on this from the rust side, we are just going to list that you need to have these 2/3 crates available in scope - and not renamed - for kube-derive to work.