fix: Correctly report missing Spec suffix

Author: Techassi

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

@@ -1,6 +1,6 @@
 use std::ops::Not;
 
-use darling::{util::IdentString, FromAttributes, Result};
+use darling::{util::IdentString, Error, FromAttributes, Result};
 use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{parse_quote, ItemStruct, Path};
@@ -32,6 +32,15 @@ impl Container {
         }
 
         let kubernetes_options = attributes.kubernetes_arguments.map(Into::into);
+        let idents: ContainerIdents = item_struct.ident.into();
+
+        // Validate K8s specific requirements
+        // Ensure that the struct name includes the 'Spec' suffix.
+        if kubernetes_options.is_some() && !idents.original.as_str().ends_with("Spec") {
+            return Err(Error::custom(
+                "struct name needs to include the `Spec` suffix if Kubernetes features are enabled via `#[versioned(k8s())]`"
+            ).with_span(&idents.original.span()));
+        }
 
         let options = ContainerOptions {
             skip_from: attributes
@@ -42,8 +51,6 @@ impl Container {
             kubernetes_options,
         };
 
-        let idents: ContainerIdents = item_struct.ident.into();
-
         let common = CommonContainerData {
             original_attributes: item_struct.attrs,
             options,
@@ -71,6 +78,15 @@ impl Container {
         }
 
         let kubernetes_options = attributes.kubernetes_arguments.map(Into::into);
+        let idents: ContainerIdents = item_struct.ident.into();
+
+        // Validate K8s specific requirements
+        // Ensure that the struct name includes the 'Spec' suffix.
+        if kubernetes_options.is_some() && !idents.original.as_str().ends_with("Spec") {
+            return Err(Error::custom(
+                "struct name needs to include the `Spec` suffix if Kubernetes features are enabled via `#[versioned(k8s())]`"
+            ).with_span(&idents.original.span()));
+        }
 
         let options = ContainerOptions {
             skip_from: attributes
@@ -80,8 +96,6 @@ impl Container {
             kubernetes_options,
         };
 
-        let idents: ContainerIdents = item_struct.ident.into();
-
         // Nested structs
         // We need to filter out the `versioned` attribute, because these are not directly processed
         // by darling, but instead by us (using darling). For this reason, darling won't remove the