feat(versioned): Add support to pass the scale argument (#1185)

* feat(versioned): Add support to pass the scale argument

* test(versioned): Add snapshot test for scale argument

* chore(versioned): Add changelog entry

* refactor: Destructure Scale struct during token generation

Co-authored-by: Sebastian Bernauer <sebastian.bernauer@stackable.tech>

---------

Co-authored-by: Sebastian Bernauer <sebastian.bernauer@stackable.tech>

Author: Techassi

crates/stackable-versioned-macros/src/attrs/container.rs

@@ -50,6 +50,7 @@ pub struct ContainerSkipArguments {
 ///   cluster scoped resource.
 /// - `crates`: Override specific crates.
 /// - `status`: Set the specified struct as the status subresource.
+/// - `scale`: Configure the scale subresource for horizontal pod autoscaling integration.
 /// - `shortname`: Set a shortname for the CR object. This can be specified multiple
 ///   times.
 /// - `skip`: Controls skipping parts of the generation.
@@ -64,7 +65,7 @@ pub struct StructCrdArguments {
     pub status: Option<Path>,
     // derive
     // schema
-    // scale
+    pub scale: Option<Scale>,
     // printcolumn
     #[darling(multiple, rename = "shortname")]
     pub shortnames: Vec<String>,
@@ -74,3 +75,21 @@ pub struct StructCrdArguments {
     // annotation
     // label
 }
+
+/// Scale subresource configuration for a CRD.
+///
+/// Mirrors the fields of [`k8s_openapi::CustomResourceSubresourceScale`][1] and what is present in
+/// `kube_derive`.
+///
+/// [1]: k8s_openapi::apiextensions_apiserver::pkg::apis::apiextensions::v1::CustomResourceSubresourceScale
+//
+// TODO (@Techassi): This should eventually get replaced by directly using what `kube_derive` offers,
+// but that requires an upstream restructure I'm planning to do soon(ish).
+#[derive(Clone, Debug, FromMeta)]
+pub struct Scale {
+    pub spec_replicas_path: String,
+    pub status_replicas_path: String,
+
+    #[darling(default)]
+    pub label_selector_path: Option<String>,
+}

crates/stackable-versioned-macros/src/codegen/container/struct/mod.rs

@@ -5,7 +5,7 @@ use quote::quote;
 use syn::{Generics, ItemStruct};
 
 use crate::{
-    attrs::container::{ContainerAttributes, StructCrdArguments},
+    attrs::container::{ContainerAttributes, Scale, StructCrdArguments},
     codegen::{
         Direction, VersionContext, VersionDefinition,
         changes::Neighbors,
@@ -272,6 +272,28 @@ impl Struct {
             _ => None,
         };
 
+        let scale = spec_gen_ctx
+            .kubernetes_arguments
+            .scale
+            .as_ref()
+            .map(|scale| {
+                let Scale {
+                    spec_replicas_path,
+                    status_replicas_path,
+                    label_selector_path,
+                } = scale;
+
+                let label_selector_path = label_selector_path
+                    .as_ref()
+                    .map(|p| quote! { , label_selector_path = #p });
+
+                quote! { , scale(
+                    spec_replicas_path = #spec_replicas_path,
+                    status_replicas_path = #status_replicas_path
+                    #label_selector_path
+                )}
+            });
+
         let shortnames: TokenStream = spec_gen_ctx
             .kubernetes_arguments
             .shortnames
@@ -286,7 +308,7 @@ impl Struct {
                 // These must be comma separated (except the last) as they always exist:
                 group = #group, version = #version, kind = #kind
                 // These fields are optional, and therefore the token stream must prefix each with a comma:
-                #singular #plural #namespaced #crates #status #shortnames
+                #singular #plural #namespaced #crates #status #scale #shortnames
             )]
         })
     }

crates/stackable-versioned-macros/tests/inputs/pass/scale.rs

@@ -0,0 +1,28 @@
+use stackable_versioned::versioned;
+// ---
+#[versioned(version(name = "v1alpha1"))]
+// ---
+pub(crate) mod versioned {
+    #[versioned(crd(
+        group = "stackable.tech",
+        scale(
+            spec_replicas_path = ".spec.replicas",
+            status_replicas_path = ".status.replicas",
+            label_selector_path = ".status.selector"
+        )
+    ))]
+    #[derive(
+        Clone,
+        Debug,
+        serde::Deserialize,
+        serde::Serialize,
+        schemars::JsonSchema,
+        kube::CustomResource,
+    )]
+    struct FooSpec {
+        bar: usize,
+        baz: bool,
+    }
+}
+// ---
+fn main() {}

crates/stackable-versioned-macros/tests/snapshots/stackable_versioned_macros__snapshots__pass@scale.rs.snap

@@ -30,6 +30,7 @@ mod inputs {
         // mod module_preserve;
         // mod renamed_field;
         // mod renamed_kind;
+        // mod scale;
         // mod shortnames;
         // mod submodule;
     }

crates/stackable-versioned-macros/tests/trybuild.rs

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Added
+
+- Add support to provide `#[versioned(crd(scale(...)))]` argument to enable the `/scale` subresource ([#1185]).
+
+[#1185]: https://github.com/stackabletech/operator-rs/pull/1185
+
 ## [0.8.3] - 2025-10-23
 
 ### Fixed