From b6d84ad7efd47d4efe64b7078064f7c1ce874ec5 Mon Sep 17 00:00:00 2001
From: Leon Michalski <leonmk@amazon.de>
Date: Tue, 2 Dec 2025 15:58:33 +0000
Subject: [PATCH] fix(typewriter): struct cannot extend strucs

---
 .../typewriter/src/renderer/typescript.ts     |  6 ++++
 packages/@cdklabs/typewriter/src/struct.ts    |  4 +++
 .../typewriter/test/interface.test.ts         | 36 ++++++++++++++++++-
 3 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/packages/@cdklabs/typewriter/src/renderer/typescript.ts b/packages/@cdklabs/typewriter/src/renderer/typescript.ts
index fa0e8d936..a8207a7cb 100644
--- a/packages/@cdklabs/typewriter/src/renderer/typescript.ts
+++ b/packages/@cdklabs/typewriter/src/renderer/typescript.ts
@@ -128,6 +128,12 @@ export class TypeScriptRenderer extends Renderer {
     this.renderDocs(structType, { forceStruct: true });
     this.emit(`${modifiers}interface ${structType.name}`);
     this.renderTypeParameters(structType.typeParameters);
+
+    if (structType.extends.length > 0) {
+      this.emit(' extends ');
+      this.emitList(structType.extends, ', ', (t) => this.renderType(t));
+    }
+
     this.emitBlock(' ', () => {
       const props = Array.from(structType.properties.values()).filter((p) => p.visibility === MemberVisibility.Public);
 
diff --git a/packages/@cdklabs/typewriter/src/struct.ts b/packages/@cdklabs/typewriter/src/struct.ts
index a48f4d3b3..0fe5c1870 100644
--- a/packages/@cdklabs/typewriter/src/struct.ts
+++ b/packages/@cdklabs/typewriter/src/struct.ts
@@ -36,6 +36,10 @@ export class StructType extends MemberType {
     spec.properties?.forEach((p) => this.addProperty(p));
   }
 
+  public get extends() {
+    return this.spec.extends ?? [];
+  }
+
   /**
    * Adds a property to the interface
    *
diff --git a/packages/@cdklabs/typewriter/test/interface.test.ts b/packages/@cdklabs/typewriter/test/interface.test.ts
index a327f6bac..0a3775f7c 100644
--- a/packages/@cdklabs/typewriter/test/interface.test.ts
+++ b/packages/@cdklabs/typewriter/test/interface.test.ts
@@ -1,4 +1,4 @@
-import { InterfaceType, Module, TypeScriptRenderer } from '../src';
+import { InterfaceType, Module, StructType, TypeScriptRenderer } from '../src';
 
 const renderer = new TypeScriptRenderer();
 let scope: Module;
@@ -24,3 +24,37 @@ test('can update some interface spec fields after initial creation', () => {
     }"
   `);
 });
+
+test('struct can extend struct', () => {
+  new StructType(scope, {
+    name: 'MyStruct',
+    extends: [scope.type('AnotherStruct')],
+  });
+
+  expect(renderer.render(scope)).toMatchInlineSnapshot(`
+    "/* eslint-disable prettier/prettier, @stylistic/max-len */
+    /**
+     * @struct
+     */
+    interface MyStruct extends AnotherStruct {
+
+    }"
+  `);
+});
+
+test('struct can extend multiple structs', () => {
+  new StructType(scope, {
+    name: 'MyStruct',
+    extends: [scope.type('AnotherStruct'), scope.type('SecondStruct')],
+  });
+
+  expect(renderer.render(scope)).toMatchInlineSnapshot(`
+    "/* eslint-disable prettier/prettier, @stylistic/max-len */
+    /**
+     * @struct
+     */
+    interface MyStruct extends AnotherStruct, SecondStruct {
+
+    }"
+  `);
+});