FlaUI · aristotelos · May 14, 2024 · May 8, 2024 · May 13, 2024 · May 13, 2024
diff --git a/src/FlaUI.WebDriver.UITests/FindElementsTests.cs b/src/FlaUI.WebDriver.UITests/FindElementsTests.cs
@@ -227,6 +227,23 @@ public void FindElements_InOtherWindow_ReturnsEmptyList()
             Assert.That(elementsInNewWindow, Has.Count.EqualTo(1));
         }
 
+        [Test]
+        public void FindElements_AfterPreviousKnownElementUnavailable_DoesNotThrow()
+        {
+            var driverOptions = FlaUIDriverOptions.TestApp();
+            using var driver = new RemoteWebDriver(WebDriverFixture.WebDriverUrl, driverOptions);
+            var initialWindowHandle = driver.CurrentWindowHandle;
+            OpenAndSwitchToAnotherWindow(driver);
+            var elementInNewWindow = driver.FindElement(ExtendedBy.AccessibilityId("Window1TextBox"));
+            // close to make the elementInNewWindow unavailable
+            driver.Close();
+            driver.SwitchTo().Window(initialWindowHandle);
+
+            var foundElements = driver.FindElements(ExtendedBy.AccessibilityId("TextBox"));
+
+            Assert.That(foundElements, Has.Count.EqualTo(1));
+        }
+
         private static void OpenAndSwitchToAnotherWindow(RemoteWebDriver driver)
         {
             var initialWindowHandles = new[] { driver.CurrentWindowHandle };

diff --git a/src/FlaUI.WebDriver/ISessionRepository.cs b/src/FlaUI.WebDriver/ISessionRepository.cs
@@ -4,6 +4,7 @@ public interface ISessionRepository
     {
         void Add(Session session);
         void Delete(Session session);
+        List<Session> FindAll();
         Session? FindById(string sessionId);
         List<Session> FindTimedOut();
     }

diff --git a/src/FlaUI.WebDriver/KnownElement.cs b/src/FlaUI.WebDriver/KnownElement.cs
@@ -4,13 +4,22 @@ namespace FlaUI.WebDriver
 {
     public class KnownElement
     {
-        public KnownElement(AutomationElement element)
+        public KnownElement(AutomationElement element, string? elementRuntimeId)
         {
             Element = element;
+            ElementRuntimeId = elementRuntimeId;
             ElementReference = Guid.NewGuid().ToString();
         }
 
-        public string ElementReference { get; set; }
+        public string ElementReference { get; }
+
+        /// <summary>
+        /// A temporarily unique ID, so cannot be used for identity over time, but can be used for improving performance of equality tests.
+        /// "The identifier is only guaranteed to be unique to the UI of the desktop on which it was generated. Identifiers can be reused over time."
+        /// </summary>
+        /// <seealso href="https://learn.microsoft.com/en-us/windows/win32/api/uiautomationclient/nf-uiautomationclient-iuiautomationelement-getruntimeid"/>
+        public string? ElementRuntimeId { get; }
+
         public AutomationElement Element { get; }
     }
 }
diff --git a/src/FlaUI.WebDriver/KnownWindow.cs b/src/FlaUI.WebDriver/KnownWindow.cs
@@ -4,12 +4,21 @@ namespace FlaUI.WebDriver
 {
     public class KnownWindow
     {
-        public KnownWindow(Window window)
+        public KnownWindow(Window window, string? windowRuntimeId)
         {
             Window = window;
+            WindowRuntimeId = windowRuntimeId;
             WindowHandle = Guid.NewGuid().ToString();
         }
         public string WindowHandle { get; set; }
+
+        /// <summary>
+        /// A temporarily unique ID, so cannot be used for identity over time, but can be used for improving performance of equality tests.
+        /// "The identifier is only guaranteed to be unique to the UI of the desktop on which it was generated. Identifiers can be reused over time."
+        /// </summary>
+        /// <seealso href="https://learn.microsoft.com/en-us/windows/win32/api/uiautomationclient/nf-uiautomationclient-iuiautomationelement-getruntimeid"/>
+        public string? WindowRuntimeId { get; set; }
+
         public Window Window { get; set; }
     }
 }
diff --git a/src/FlaUI.WebDriver/Session.cs b/src/FlaUI.WebDriver/Session.cs
@@ -1,6 +1,7 @@
 using FlaUI.Core;
 using FlaUI.Core.AutomationElements;
 using FlaUI.UIA3;
+using System.Runtime.InteropServices;
 
 namespace FlaUI.WebDriver
 {
@@ -77,10 +78,11 @@ public void SetLastCommandTimeToNow()
 
         public KnownElement GetOrAddKnownElement(AutomationElement element)
         {
-            var result = KnownElementsByElementReference.Values.FirstOrDefault(knownElement => knownElement.Element.Equals(element));
+            var elementRuntimeId = GetRuntimeId(element);
+            var result = KnownElementsByElementReference.Values.FirstOrDefault(knownElement => knownElement.ElementRuntimeId == elementRuntimeId && SafeElementEquals(knownElement.Element, element));
             if (result == null)
             {
-                result = new KnownElement(element);
+                result = new KnownElement(element, elementRuntimeId);
                 KnownElementsByElementReference.Add(result.ElementReference, result);
             }
             return result;
@@ -97,10 +99,11 @@ public KnownElement GetOrAddKnownElement(AutomationElement element)
 
         public KnownWindow GetOrAddKnownWindow(Window window)
         {
-            var result = KnownWindowsByWindowHandle.Values.FirstOrDefault(knownElement => knownElement.Window.Equals(window));
+            var windowRuntimeId = GetRuntimeId(window);
+            var result = KnownWindowsByWindowHandle.Values.FirstOrDefault(knownWindow => knownWindow.WindowRuntimeId == windowRuntimeId && SafeElementEquals(knownWindow.Window, window));
             if (result == null)
             {
-                result = new KnownWindow(window);
+                result = new KnownWindow(window, windowRuntimeId);
                 KnownWindowsByWindowHandle.Add(result.WindowHandle, result);
             }
             return result;
@@ -124,6 +127,26 @@ public void RemoveKnownWindow(Window window)
             }
         }
 
+        public void EvictUnavailableElements()
+        {
+            // Evict unavailable elements to prevent slowing down
+            var unavailableElements = KnownElementsByElementReference.Where(item => !item.Value.Element.IsAvailable).Select(item => item.Key).ToArray();
+            foreach (var unavailableElementKey in unavailableElements)
+            {
+                KnownElementsByElementReference.Remove(unavailableElementKey);
+            }
+        }
+
+        public void EvictUnavailableWindows()
+        {
+            // Evict unavailable windows to prevent slowing down
+            var unavailableWindows = KnownWindowsByWindowHandle.Where(item => !item.Value.Window.IsAvailable).Select(item => item.Key).ToArray();
+            foreach (var unavailableWindowKey in unavailableWindows)
+            {
+                KnownWindowsByWindowHandle.Remove(unavailableWindowKey);
+            }
+        }
+
         public void Dispose()
         {
             if (IsAppOwnedBySession && App != null && !App.HasExited)
@@ -133,5 +156,29 @@ public void Dispose()
             Automation.Dispose();
             App?.Dispose();
         }
+
+        private string? GetRuntimeId(AutomationElement element)
+        {
+            if (!element.Properties.RuntimeId.IsSupported)
+            {
+                return null;
+            }
+
+            return string.Join(",", element.Properties.RuntimeId.Value.Select(item => Convert.ToBase64String(BitConverter.GetBytes(item))));
+        }
+
+        private bool SafeElementEquals(AutomationElement element1, AutomationElement element2)
+        {
+            try
+            {
+                return element1.Equals(element2);
+            }
+            catch (COMException)
+            {
+                // May occur if the element is suddenly no longer available
+                return false;
+            }
+        }
+
     }
 }
diff --git a/src/FlaUI.WebDriver/SessionCleanupService.cs b/src/FlaUI.WebDriver/SessionCleanupService.cs
@@ -34,22 +34,38 @@ private void DoWork(object? state)
                 scope.ServiceProvider
                     .GetRequiredService<ISessionRepository>();
 
-                var timedOutSessions = sessionRepository.FindTimedOut();
-                if(timedOutSessions.Count > 0)
-                {
-                    _logger.LogInformation("Session cleanup service cleaning up {Count} sessions that did not receive commands in their specified new command timeout interval", timedOutSessions.Count);
+                RemoveTimedOutSessions(sessionRepository);
 
-                    foreach (Session session in timedOutSessions)
-                    {
-                        sessionRepository.Delete(session);
-                        session.Dispose();
-                    }
-                }
-                else
+                EvictUnavailableElements(sessionRepository);
+            }
+        }
+
+        private void EvictUnavailableElements(ISessionRepository sessionRepository)
+        {
+            foreach(var session in sessionRepository.FindAll())
+            {
+                session.EvictUnavailableElements();
+                session.EvictUnavailableWindows();
+            }
+        }
+
+        private void RemoveTimedOutSessions(ISessionRepository sessionRepository)
+        {
+            var timedOutSessions = sessionRepository.FindTimedOut();
+            if (timedOutSessions.Count > 0)
+            {
+                _logger.LogInformation("Session cleanup service cleaning up {Count} sessions that did not receive commands in their specified new command timeout interval", timedOutSessions.Count);
+
+                foreach (Session session in timedOutSessions)
                 {
-                    _logger.LogInformation("Session cleanup service did not find sessions to cleanup");
+                    sessionRepository.Delete(session);
+                    session.Dispose();
                 }
             }
+            else
+            {
+                _logger.LogInformation("Session cleanup service did not find sessions to cleanup");
+            }
         }
 
         public Task StopAsync(CancellationToken stoppingToken)

diff --git a/src/FlaUI.WebDriver/SessionRepository.cs b/src/FlaUI.WebDriver/SessionRepository.cs
@@ -23,5 +23,10 @@ public List<Session> FindTimedOut()
         {
             return Sessions.Where(session => session.IsTimedOut).ToList();
         }
+
+        public List<Session> FindAll()
+        {
+            return new List<Session>(Sessions);
+        }
     }
 }