Fixed gc of Data type

.changeset/soft-lizards-flash.md

@@ -0,0 +1,5 @@
+---
+"@firebase/data-connect": patch
+---
+
+Fixed type erasure of the `Data` type

common/api-review/data-connect.api.md

@@ -83,6 +83,9 @@ export function executeMutation<Data, Variables>(mutationRef: MutationRef<Data,
 // @public
 export function executeQuery<Data, Variables>(queryRef: QueryRef<Data, Variables>): QueryPromise<Data, Variables>;
 
+// @public (undocumented)
+export const fdcSymbol: unique symbol;
+
 // @public
 export function getDataConnect(options: ConnectorConfig): DataConnect;
 
@@ -124,7 +127,9 @@ export type OnErrorSubscription = (err?: FirebaseError) => void;
 export type OnResultSubscription<Data, Variables> = (res: QueryResult<Data, Variables>) => void;
 
 // @public (undocumented)
-export interface OperationRef<_Data, Variables> {
+export interface OperationRef<Data, Variables> {
+    // (undocumented)
+    [fdcSymbol]?: Data;
     // (undocumented)
     dataConnect: DataConnect;
     // (undocumented)

packages/data-connect/package.json

@@ -68,7 +68,7 @@
   "bugs": {
     "url": "https://github.com/firebase/firebase-js-sdk/issues"
   },
-  "typings": "dist/src/index.d.ts",
+  "typings": "./dist/public.d.ts",
   "nyc": {
     "extension": [
       ".ts"

packages/data-connect/src/api/Reference.ts

@@ -30,11 +30,14 @@ export interface OpResult<Data> {
   fetchTime: string;
 }
 
-export interface OperationRef<_Data, Variables> {
+export const fdcSymbol = Symbol();
+
+export interface OperationRef<Data, Variables> {
   name: string;
   variables: Variables;
   refType: ReferenceType;
   dataConnect: DataConnect;
+  [fdcSymbol]?: Data; // Never used, just here to ensure that the Data type doesn't get erased.
 }
 
 export interface DataConnectResult<Data, Variables> extends OpResult<Data> {

packages/data-connect/test/unit/typings.test.ts

@@ -0,0 +1,45 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ *
+ * 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 { deleteApp, initializeApp } from '@firebase/app';
+import { DataConnect, getDataConnect, QueryRef, queryRef } from '../../src/api';
+describe('Typings', () => {
+  it('should properly infer the type', async () => {
+    interface MyData {
+      extraField: boolean;
+    }
+    const app = initializeApp({ projectId: 'a' }, 'test');
+    const extendedType = Object.assign(
+      queryRef<MyData, undefined>(
+        getDataConnect({ connector: 'c', location: 'l', service: 'n' }),
+        '',
+        undefined
+      ),
+      {
+        __abc: true
+      }
+    );
+    function myFn<Data, Variables>(
+      queryRef: QueryRef<Data, Variables>
+    ): { data: Data } {
+      const data = {} as Data;
+      return { data };
+    }
+    myFn(extendedType).data.extraField;
+    await deleteApp(app);
+  });
+});