chore: move expand to @backstage/types

Signed-off-by: blam <ben@blam.sh>

packages/types/src/expand.test.ts

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { Expand, ExpandRecursive } from './expand';
+
+describe('expand', () => {
+  it('should expand type aliases into their equivalent type', () => {
+    type Test = { a: string } & { b: number };
+    // expanded type
+    type Result = Expand<Test>;
+
+    const result: Result = { a: 'string', b: 1 };
+    expect(result).toEqual({ a: 'string', b: 1 });
+  });
+
+  it('should expand types recursively', () => {
+    type Test = { a: string } & { b: { c: { e: string } } } & {
+      b: { c: { d: boolean } };
+    };
+    // expanded type
+    type Result = ExpandRecursive<Test>;
+
+    const result: Result = { a: 'string', b: { c: { e: 'string', d: true } } };
+    expect(result).toEqual({ a: 'string', b: { c: { e: 'string', d: true } } });
+  });
+});

packages/types/src/expand.ts

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Utility type to expand type aliases into their equivalent type.
+ * @public
+ */
+
+export type Expand<T> = T extends infer O ? { [K in keyof O]: O[K] } : never;
+
+/**
+ * Helper type that expands type hints recursively
+ *
+ * @public
+ */
+export type ExpandRecursive<T> = T extends infer O
+  ? { [K in keyof O]: ExpandRecursive<O[K]> }
+  : never;

packages/types/src/index.ts

@@ -24,3 +24,4 @@ export { createDeferred, type DeferredPromise } from './deferred';
 export type { JsonArray, JsonObject, JsonPrimitive, JsonValue } from './json';
 export type { Observable, Observer, Subscription } from './observable';
 export { type HumanDuration, durationToMilliseconds } from './time';
+export { type Expand, type ExpandRecursive } from './expand';