Fix/wait for at

dev/e2e_app/lib/at_finder_screen.dart

@@ -0,0 +1,95 @@
+import 'dart:async';
+
+import 'package:e2e_app/keys.dart';
+import 'package:flutter/material.dart';
+
+class AtFinderScreen extends StatefulWidget {
+  const AtFinderScreen({super.key});
+
+  @override
+  State<AtFinderScreen> createState() => _AtFinderScreenState();
+}
+
+class _AtFinderScreenState extends State<AtFinderScreen> {
+  var _isFirstItemVisible = false;
+  var _isSecondItemVisible = false;
+  var _firstItemTapped = 0;
+  var _secondItemTapped = 0;
+
+  @override
+  void initState() {
+    super.initState();
+
+    unawaited(
+      Future<void>.delayed(const Duration(seconds: 1)).then((_) {
+        if (!mounted) {
+          return;
+        }
+
+        setState(() {
+          _isFirstItemVisible = true;
+        });
+      }),
+    );
+
+    unawaited(
+      Future<void>.delayed(const Duration(seconds: 3)).then((_) {
+        if (!mounted) {
+          return;
+        }
+
+        setState(() {
+          _isSecondItemVisible = true;
+        });
+      }),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('at() finder')),
+      body: ListView(
+        children: [
+          if (_isFirstItemVisible)
+            AtFinderItem(
+              onTap: () {
+                setState(() {
+                  _firstItemTapped++;
+                });
+              },
+            ),
+          if (_isSecondItemVisible)
+            AtFinderItem(
+              onTap: () {
+                setState(() {
+                  _secondItemTapped++;
+                });
+              },
+            ),
+          if (_secondItemTapped > 0)
+            Text(
+              'Second item tapped $_secondItemTapped',
+              key: K.atFinderSecondItemTapped,
+            ),
+          if (_firstItemTapped > 0)
+            Text(
+              'First item tapped $_firstItemTapped',
+              key: K.atFinderFirstItemTapped,
+            ),
+        ],
+      ),
+    );
+  }
+}
+
+class AtFinderItem extends StatelessWidget {
+  const AtFinderItem({super.key, required this.onTap});
+
+  final VoidCallback onTap;
+
+  @override
+  Widget build(BuildContext context) {
+    return ListTile(key: K.atFinderItem, title: Text('Item'), onTap: onTap);
+  }
+}

dev/e2e_app/lib/keys.dart

@@ -10,6 +10,12 @@ class Keys {
   static const bottomText = Key('bottomText');
   static const backButton = Key('backButton');
 
+  // at() finder screen
+  static const atFinderFirstItemTapped = Key('atFinderFirstItemTapped');
+  static const atFinderItem = Key('atFinderItem');
+  static const atFinderScreenButton = Key('atFinderScreenButton');
+  static const atFinderSecondItemTapped = Key('atFinderSecondItemTapped');
+
   // autofocus text field flow
   static const usernameTextField = Key('usernameTextField');
   static const usernameNextButton = Key('usernameNextButton');
@@ -82,3 +88,7 @@ class Keys {
   static const smallImagePreview = Key('smallImagePreview');
   static const selectedPhotosCount = Key('selectedPhotosCount');
 }
+
+class AtFinderItemKey extends ValueKey<int> {
+  const AtFinderItemKey(super.value);
+}

dev/e2e_app/lib/main.dart

@@ -1,5 +1,6 @@
 import 'package:app_links/app_links.dart';
 import 'package:e2e_app/applink_screen.dart';
+import 'package:e2e_app/at_finder_screen.dart';
 import 'package:e2e_app/camera_screen.dart';
 import 'package:e2e_app/keys.dart';
 import 'package:e2e_app/loading_screen.dart';
@@ -212,6 +213,13 @@ class _ExampleHomePageState extends State<ExampleHomePage> {
             ),
             child: const Text('Open loading screen'),
           ),
+          TextButton(
+            key: K.atFinderScreenButton,
+            onPressed: () => Navigator.of(context).push(
+              MaterialPageRoute<void>(builder: (_) => const AtFinderScreen()),
+            ),
+            child: const Text('Open at() finder screen'),
+          ),
           TextButton(
             onPressed: () => Navigator.of(context).push(
               MaterialPageRoute<void>(builder: (_) => const LocationScreen()),

dev/e2e_app/patrol_test/at_finder_test.dart

@@ -0,0 +1,22 @@
+import 'package:e2e_app/keys.dart';
+
+import 'common.dart';
+
+void main() {
+  patrol(
+    'at() waits until widget at index exists',
+    ($) async {
+      await createApp($);
+      await $(K.atFinderScreenButton).scrollTo().tap();
+
+      await $(K.atFinderItem).at(1).tap();
+      await $(K.atFinderItem).first.tap();
+      await $(K.atFinderItem).last.tap();
+
+      await $(K.atFinderFirstItemTapped).waitUntilVisible();
+      await $(K.atFinderSecondItemTapped).waitUntilVisible();
+      expect($(K.atFinderSecondItemTapped).text, 'Second item tapped 2');
+    },
+    tags: ['android', 'emulator', 'ios', 'simulator'],
+  );
+}

packages/patrol_finders/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## Unreleased
 
+- Fix `at()`, `first` and `last` to wait for widget to become visible.
 - Add `isAndroid`, `isIOS`, `isWeb` and `isMacOS` getters.
 - Remove `dart:io`.
 

packages/patrol_finders/lib/src/custom_finders/patrol_finder.dart

@@ -541,20 +541,52 @@ class PatrolFinder implements MatchFinder {
 
   @override
   PatrolFinder get first {
-    // TODO: Throw a better error (https://github.com/leancodepl/patrol/issues/548)
-    return PatrolFinder(tester: tester, finder: finder.first);
+    return _select(
+      description: 'first',
+      selector: (candidates) => candidates.take(1),
+    );
   }
 
   @override
   PatrolFinder get last {
-    // TODO: Throw a better error (https://github.com/leancodepl/patrol/issues/548)
-    return PatrolFinder(tester: tester, finder: finder.last);
+    return _select(
+      description: 'last',
+      selector: (candidates) {
+        if (candidates.isEmpty) {
+          return const Iterable<Element>.empty();
+        }
+
+        return [candidates.last] as Iterable<Element>;
+      },
+    );
   }
 
   @override
   PatrolFinder at(int index) {
-    // TODO: Throw a better error (https://github.com/leancodepl/patrol/issues/548)
-    return PatrolFinder(tester: tester, finder: finder.at(index));
+    return _select(
+      description: 'index $index',
+      selector: (candidates) {
+        if (index < 0) {
+          return const Iterable<Element>.empty();
+        }
+
+        return candidates.skip(index).take(1);
+      },
+    );
+  }
+
+  PatrolFinder _select({
+    required String description,
+    required Iterable<Element> Function(Iterable<Element> candidates) selector,
+  }) {
+    return PatrolFinder(
+      tester: tester,
+      finder: _PatrolSelectorFinder(
+        finder,
+        selectorDescription: description,
+        selector: selector,
+      ),
+    );
   }
 
   @override
@@ -611,6 +643,30 @@ class PatrolFinder implements MatchFinder {
   bool precache() => finder.precache();
 }
 
+class _PatrolSelectorFinder extends ChainedFinder {
+  _PatrolSelectorFinder(
+    super.parent, {
+    required this.selectorDescription,
+    required this.selector,
+  });
+
+  final String selectorDescription;
+  final Iterable<Element> Function(Iterable<Element> candidates) selector;
+
+  @override
+  Iterable<Element> filter(Iterable<Element> parentCandidates) =>
+      selector(parentCandidates);
+
+  @override
+  String describeMatch(Plurality plurality) {
+    return '${parent.describeMatch(plurality)} '
+        '(ignoring all but $selectorDescription)';
+  }
+
+  @override
+  String get description => describeMatch(Plurality.many);
+}
+
 /// Useful methods that make chained finders more readable.
 extension ActionCombiner on Future<PatrolFinder> {
   /// Same as [PatrolFinder.tap], but on a [PatrolFinder] which is not yet