feat(stackable-versioned): Add support for generics (#969)

* chore: Add generics to Struct struct

* feat: Add basic generics support for enums

* feat: Add basic generics support for structs

* test: Add snapshot tests for generics

* chore: Add changelog entry

Author: Techassi

crates/stackable-versioned-macros/fixtures/inputs/default/generics_enum.rs

@@ -0,0 +1,9 @@
+#[versioned(version(name = "v1alpha1"), version(name = "v1"))]
+// ---
+pub enum Foo<T>
+where
+    T: Default,
+{
+    Bar(T),
+    Baz,
+}

crates/stackable-versioned-macros/fixtures/inputs/default/generics_module.rs

@@ -0,0 +1,23 @@
+#[versioned(
+    version(name = "v1alpha1"),
+    version(name = "v1"),
+    options(preserve_module)
+)]
+// ---
+pub mod versioned {
+    struct Foo<T>
+    where
+        T: Default,
+    {
+        bar: T,
+        baz: u8,
+    }
+
+    enum Boom<T>
+    where
+        T: Default,
+    {
+        Big(T),
+        Shaq,
+    }
+}

crates/stackable-versioned-macros/fixtures/inputs/default/generics_struct.rs

@@ -0,0 +1,9 @@
+#[versioned(version(name = "v1alpha1"), version(name = "v1"))]
+// ---
+pub struct Foo<T>
+where
+    T: Default,
+{
+    bar: T,
+    baz: u8,
+}

crates/stackable-versioned-macros/fixtures/snapshots/stackable_versioned_macros__test__default_snapshots@generics_enum.rs.snap

@@ -3,7 +3,7 @@ use std::ops::Not;
 use darling::{util::IdentString, FromAttributes, Result};
 use proc_macro2::TokenStream;
 use quote::quote;
-use syn::ItemEnum;
+use syn::{Generics, ItemEnum};
 
 use crate::{
     attrs::container::NestedContainerAttributes,
@@ -46,6 +46,7 @@ impl Container {
         };
 
         Ok(Self::Enum(Enum {
+            generics: item_enum.generics,
             variants: versioned_variants,
             common,
         }))
@@ -82,6 +83,7 @@ impl Container {
         };
 
         Ok(Self::Enum(Enum {
+            generics: item_enum.generics,
             variants: versioned_variants,
             common,
         }))
@@ -96,12 +98,16 @@ pub(crate) struct Enum {
 
     /// Common container data which is shared between enums and structs.
     pub(crate) common: CommonContainerData,
+
+    /// Generic types of the enum
+    pub generics: Generics,
 }
 
 // Common token generation
 impl Enum {
     /// Generates code for the enum definition.
     pub(crate) fn generate_definition(&self, version: &VersionDefinition) -> TokenStream {
+        let (_, type_generics, where_clause) = self.generics.split_for_impl();
         let original_attributes = &self.common.original_attributes;
         let ident = &self.common.idents.original;
         let version_docs = &version.docs;
@@ -114,7 +120,7 @@ impl Enum {
         quote! {
             #(#[doc = #version_docs])*
             #(#original_attributes)*
-            pub enum #ident {
+            pub enum #ident #type_generics #where_clause {
                 #variants
             }
         }
@@ -133,6 +139,12 @@ impl Enum {
 
         match next_version {
             Some(next_version) => {
+                // TODO (@Techassi): Support generic types which have been removed in newer versions,
+                // but need to exist for older versions How do we represent that? Because the
+                // defined struct always represents the latest version. I guess we could generally
+                // advise against using generic types, but if you have to, avoid removing it in
+                // later versions.
+                let (impl_generics, type_generics, where_clause) = self.generics.split_for_impl();
                 let enum_ident = &self.common.idents.original;
                 let from_ident = &self.common.idents.from;
 
@@ -158,8 +170,10 @@ impl Enum {
                 Some(quote! {
                     #automatically_derived
                     #allow_attribute
-                    impl ::std::convert::From<#version_ident::#enum_ident> for #next_version_ident::#enum_ident {
-                        fn from(#from_ident: #version_ident::#enum_ident) -> Self {
+                    impl #impl_generics ::std::convert::From<#version_ident::#enum_ident #type_generics> for #next_version_ident::#enum_ident #type_generics
+                        #where_clause
+                    {
+                        fn from(#from_ident: #version_ident::#enum_ident #type_generics) -> Self {
                             match #from_ident {
                                 #variants
                             }

crates/stackable-versioned-macros/fixtures/snapshots/stackable_versioned_macros__test__default_snapshots@generics_module.rs.snap

@@ -3,7 +3,7 @@ use std::ops::Not;
 use darling::{util::IdentString, Error, FromAttributes, Result};
 use proc_macro2::TokenStream;
 use quote::{quote, ToTokens};
-use syn::{parse_quote, ItemStruct, Path, Visibility};
+use syn::{parse_quote, Generics, ItemStruct, Path, Visibility};
 
 use crate::{
     attrs::container::NestedContainerAttributes,
@@ -58,6 +58,7 @@ impl Container {
         };
 
         Ok(Self::Struct(Struct {
+            generics: item_struct.generics,
             fields: versioned_fields,
             common,
         }))
@@ -113,6 +114,7 @@ impl Container {
         };
 
         Ok(Self::Struct(Struct {
+            generics: item_struct.generics,
             fields: versioned_fields,
             common,
         }))
@@ -123,16 +125,20 @@ impl Container {
 pub(crate) struct Struct {
     /// List of fields defined in the original struct. How, and if, an item
     /// should generate code, is decided by the currently generated version.
-    pub(crate) fields: Vec<VersionedField>,
+    pub fields: Vec<VersionedField>,
 
     /// Common container data which is shared between structs and enums.
-    pub(crate) common: CommonContainerData,
+    pub common: CommonContainerData,
+
+    /// Generic types of the struct
+    pub generics: Generics,
 }
 
 // Common token generation
 impl Struct {
     /// Generates code for the struct definition.
     pub(crate) fn generate_definition(&self, version: &VersionDefinition) -> TokenStream {
+        let (_, type_generics, where_clause) = self.generics.split_for_impl();
         let original_attributes = &self.common.original_attributes;
         let ident = &self.common.idents.original;
         let version_docs = &version.docs;
@@ -149,7 +155,7 @@ impl Struct {
             #(#[doc = #version_docs])*
             #(#original_attributes)*
             #kube_attribute
-            pub struct #ident {
+            pub struct #ident #type_generics #where_clause {
                 #fields
             }
         }
@@ -168,6 +174,12 @@ impl Struct {
 
         match next_version {
             Some(next_version) => {
+                // TODO (@Techassi): Support generic types which have been removed in newer versions,
+                // but need to exist for older versions How do we represent that? Because the
+                // defined struct always represents the latest version. I guess we could generally
+                // advise against using generic types, but if you have to, avoid removing it in
+                // later versions.
+                let (impl_generics, type_generics, where_clause) = self.generics.split_for_impl();
                 let struct_ident = &self.common.idents.original;
                 let from_struct_ident = &self.common.idents.from;
 
@@ -194,8 +206,10 @@ impl Struct {
                 Some(quote! {
                     #automatically_derived
                     #allow_attribute
-                    impl ::std::convert::From<#from_module_ident::#struct_ident> for #for_module_ident::#struct_ident {
-                        fn from(#from_struct_ident: #from_module_ident::#struct_ident) -> Self {
+                    impl #impl_generics ::std::convert::From<#from_module_ident::#struct_ident #type_generics> for #for_module_ident::#struct_ident #type_generics
+                        #where_clause
+                    {
+                        fn from(#from_struct_ident: #from_module_ident::#struct_ident #type_generics) -> Self {
                             Self {
                                 #fields
                             }

crates/stackable-versioned-macros/fixtures/snapshots/stackable_versioned_macros__test__default_snapshots@generics_struct.rs.snap

@@ -4,11 +4,16 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Added
+
+- Add basic support for generic types in struct and enum definitions ([#969]).
+
 ### Changed
 
 - BREAKING: Move `preserve_module` option into `options` to unify option interface ([#961]).
 
 [#961]: https://github.com/stackabletech/operator-rs/pull/961
+[#969]: https://github.com/stackabletech/operator-rs/pull/969
 
 ## [0.5.1] - 2025-02-14