Make tester.startGesture less async, for better stack traces (#123946)

Make tester.startGesture less async, for better stack traces

packages/flutter_test/lib/src/controller.dart

@@ -1133,6 +1133,19 @@ abstract class WidgetController {
     return result;
   }
 
+  TestGesture _createGesture({
+    int? pointer,
+    required PointerDeviceKind kind,
+    required int buttons,
+  }) {
+    return TestGesture(
+      dispatcher: sendEventToBinding,
+      kind: kind,
+      pointer: pointer ?? _getNextPointer(),
+      buttons: buttons,
+    );
+  }
+
   /// Creates gesture and returns the [TestGesture] object which you can use
   /// to continue the gesture using calls on the [TestGesture] object.
   ///
@@ -1143,12 +1156,7 @@ abstract class WidgetController {
     PointerDeviceKind kind = PointerDeviceKind.touch,
     int buttons = kPrimaryButton,
   }) async {
-    return TestGesture(
-      dispatcher: sendEventToBinding,
-      kind: kind,
-      pointer: pointer ?? _getNextPointer(),
-      buttons: buttons,
-    );
+    return _createGesture(pointer: pointer, kind: kind, buttons: buttons);
   }
 
   /// Creates a gesture with an initial appropriate starting gesture at a
@@ -1172,11 +1180,7 @@ abstract class WidgetController {
     PointerDeviceKind kind = PointerDeviceKind.touch,
     int buttons = kPrimaryButton,
   }) async {
-    final TestGesture result = await createGesture(
-      pointer: pointer,
-      kind: kind,
-      buttons: buttons,
-    );
+    final TestGesture result = _createGesture(pointer: pointer, kind: kind, buttons: buttons);
     if (kind == PointerDeviceKind.trackpad) {
       await result.panZoomStart(downLocation);
     } else {

packages/flutter_test/test/controller_test.dart

@@ -7,6 +7,7 @@ import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/semantics.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:stack_trace/stack_trace.dart';
 
 class TestDragData {
   const TestDragData(
@@ -555,6 +556,34 @@ void main() {
     },
   );
 
+  testWidgets(
+    'WidgetTester.tap appears in stack trace on error',
+    (WidgetTester tester) async {
+      // Regression test from https://github.com/flutter/flutter/pull/123946
+      await tester.pumpWidget(
+          const MaterialApp(home: Scaffold(body: Text('target'))));
+
+      final TestGesture gesture = await tester.startGesture(
+        tester.getCenter(find.text('target')), pointer: 1);
+      addTearDown(() => gesture.up());
+
+      Trace? stackTrace;
+      try {
+        await tester.tap(find.text('target'), pointer: 1);
+      } on Error catch (e) {
+        stackTrace = Trace.from(e.stackTrace!);
+      }
+      expect(stackTrace, isNotNull);
+
+      final int tapFrame = stackTrace!.frames.indexWhere(
+              (Frame frame) => frame.member == 'WidgetController.tap');
+      expect(tapFrame, greaterThanOrEqualTo(0));
+      expect(stackTrace.frames[tapFrame].package, 'flutter_test');
+      expect(stackTrace.frames[tapFrame+1].member, 'main.<fn>');
+      expect(stackTrace.frames[tapFrame+1].package, null);
+    },
+  );
+
   testWidgets(
     'ensureVisible: scrolls to make widget visible',
     (WidgetTester tester) async {