dataconnect: test: Add integration tests for operations with empty selection sets.

This feature was added to the Data Connect emulator version 2.14.0,
which is part of firebase-tools 14.18.0.

Googlers see b/448629126 for details.

Author: dconeybe

firebase-dataconnect/connectors/src/androidTest/kotlin/com/google/firebase/dataconnect/connectors/demo/EmptySelectionSetIntegrationTest.kt

@@ -0,0 +1,48 @@
+/*
+ * 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.
+ */
+package com.google.firebase.dataconnect.connectors.demo
+
+import com.google.firebase.dataconnect.connectors.demo.testutil.DemoConnectorIntegrationTestBase
+import com.google.firebase.dataconnect.testutil.property.arbitrary.dataConnect
+import io.kotest.assertions.withClue
+import io.kotest.matchers.nulls.shouldNotBeNull
+import io.kotest.matchers.shouldBe
+import io.kotest.property.Arb
+import io.kotest.property.arbitrary.next
+import kotlinx.coroutines.test.runTest
+import org.junit.Test
+
+class EmptySelectionSetIntegrationTest : DemoConnectorIntegrationTestBase() {
+
+  @Test
+  fun queryWithEmptySelectionSet() = runTest {
+    val id = Arb.dataConnect.id().next(rs)
+    val queryResult = connector.getFooByIdEmptySelectionSet.execute(id)
+    queryResult.data shouldBe Unit
+  }
+
+  @Test
+  fun mutationWithEmptySelectionSet() = runTest {
+    val id = Arb.dataConnect.id().next(rs)
+    val barValue = "bar" + Arb.dataConnect.id().next(rs)
+
+    val mutationResult = connector.upsertFooEmptySelectionSet.execute(id) { bar = barValue }
+
+    withClue("mutationResult.data") { mutationResult.data shouldBe Unit }
+    val foo = withClue("getFooById") { connector.getFooById.execute(id).data.foo.shouldNotBeNull() }
+    withClue("foo.bar") { foo.bar shouldBe barValue }
+  }
+}

firebase-dataconnect/emulator/dataconnect/connector/demo/demo_ops.gql

@@ -70,6 +70,16 @@ query GetHardcodedFoo
   }
 }
 
+# This is an example mutation that has an empty selection set (Googlers see b/448629126).
+mutation UpsertFooEmptySelectionSet($id: String!, $bar: String) @auth(level: PUBLIC) {
+  foo_upsert(data: {id: $id, bar: $bar}) @redact
+}
+
+# This is an example query that has an empty selection set (Googlers see b/448629126).
+query GetFooByIdEmptySelectionSet($id: String!) @auth(level: PUBLIC) {
+  foo(id: $id) @redact { bar }
+}
+
 mutation InsertStringVariants(
   $nonNullWithNonEmptyValue: String!,
   $nonNullWithEmptyValue: String!,