Merge pull request #90 from FlaUI/error-handling

Improve error handling of unhandled exceptions and timeouts on loading the main window

Author: aristotelos

src/FlaUI.WebDriver.UITests/SessionTests.cs

@@ -359,5 +359,15 @@ public void NewCommandTimeout_InvalidValue_Throws(object value)
             Assert.That(() => new RemoteWebDriver(WebDriverFixture.WebDriverUrl, driverOptions), 
                 Throws.TypeOf<WebDriverArgumentException>().With.Message.EqualTo("Capability appium:newCommandTimeout must be a number"));
         }
+
+        [Test]
+        public void UnknownCommand_Default_ReturnsError()
+        {
+            var driverOptions = FlaUIDriverOptions.TestApp();
+            using var driver = new RemoteWebDriver(WebDriverFixture.WebDriverUrl, driverOptions);
+
+            Assert.That(() => driver.Manage().Cookies.DeleteAllCookies(),
+                Throws.TypeOf<System.NotImplementedException>().With.Message.EqualTo("Unknown command"));
+        }
     }
 }

src/FlaUI.WebDriver/Controllers/ErrorController.cs

@@ -0,0 +1,33 @@
+using FlaUI.WebDriver.Models;
+using Microsoft.AspNetCore.Diagnostics;
+using Microsoft.AspNetCore.Mvc;
+
+namespace FlaUI.WebDriver.Controllers
+{
+    [ApiController]
+    [ApiExplorerSettings(IgnoreApi = true)]
+    public class ErrorController : ControllerBase
+    {
+        private readonly ILogger<ErrorController> _logger;
+
+
+        public ErrorController(ILogger<ErrorController> logger) {
+            _logger = logger;
+        }
+
+        [Route("/error")]
+        public IActionResult HandleError() {
+            var exceptionHandlerFeature = HttpContext.Features.Get<IExceptionHandlerFeature>()!;
+            
+            _logger.LogError(exceptionHandlerFeature.Error, "Returning WebDriver error response with error code 'unknown error'");
+
+            return new ObjectResult(new ResponseWithValue<ErrorResponse>(new ErrorResponse { 
+                ErrorCode = "unknown error", 
+                Message = exceptionHandlerFeature.Error.Message, 
+                StackTrace = exceptionHandlerFeature.Error.StackTrace ?? "" }))
+            {
+                StatusCode = 500
+            };
+        }
+    }
+}

src/FlaUI.WebDriver/NotFoundMiddleware.cs

@@ -0,0 +1,47 @@
+using FlaUI.WebDriver.Models;
+
+namespace FlaUI.WebDriver
+{
+    public class NotFoundMiddleware
+    {
+        private readonly RequestDelegate _next;
+        private readonly ILogger _logger;
+
+        public NotFoundMiddleware(RequestDelegate next, ILogger<NotFoundMiddleware> logger)
+        {
+            _next = next;
+            _logger = logger;
+        }
+
+        public async Task Invoke(HttpContext httpContext)
+        {
+            await _next(httpContext);
+            if (!httpContext.Response.HasStarted)
+            {
+                if (httpContext.Response.StatusCode == StatusCodes.Status404NotFound)
+                {
+                    _logger.LogError("Unknown endpoint {Path}", SanitizeForLog(httpContext.Request.Path.ToString()));
+                    await httpContext.Response.WriteAsJsonAsync(new ResponseWithValue<ErrorResponse>(new ErrorResponse
+                    {
+                        ErrorCode = "unknown command",
+                        Message = "Unknown command"
+                    }));
+                }
+                else if (httpContext.Response.StatusCode == StatusCodes.Status405MethodNotAllowed)
+                {
+                    _logger.LogError("Unknown method {Method} for endpoint {Path}", SanitizeForLog(httpContext.Request.Method), SanitizeForLog(httpContext.Request.Path.ToString()));
+                    await httpContext.Response.WriteAsJsonAsync(new ResponseWithValue<ErrorResponse>(new ErrorResponse
+                    {
+                        ErrorCode = "unknown method",
+                        Message = "Unknown method for this endpoint"
+                    }));
+                }
+            }
+        }
+
+        private static string SanitizeForLog(string str)
+        {
+            return str.Replace("\r", "").Replace("\n", "");
+        }
+    }
+}

src/FlaUI.WebDriver/Program.cs

@@ -24,6 +24,10 @@
 
 var app = builder.Build();
 
+app.UseMiddleware<NotFoundMiddleware>();
+
+app.UseExceptionHandler("/error");
+
 // Configure the HTTP request pipeline.
 if (app.Environment.IsDevelopment())
 {

src/FlaUI.WebDriver/Session.cs

@@ -20,7 +20,12 @@ public Session(Application? app, bool isAppOwnedBySession)
             if (app != null)
             {
                 // We have to capture the initial window handle to be able to keep it stable
-                CurrentWindowWithHandle = GetOrAddKnownWindow(app.GetMainWindow(Automation, PageLoadTimeout));
+                var mainWindow = app.GetMainWindow(Automation, PageLoadTimeout);
+                if (mainWindow == null)
+                {
+                    throw WebDriverResponseException.Timeout($"Could not get the main window of the app within the page load timeout (${PageLoadTimeout.TotalMilliseconds}ms)");
+                }
+                CurrentWindowWithHandle = GetOrAddKnownWindow(mainWindow);
             }
         }
 

src/FlaUI.WebDriver/WebDriverExceptionFilter.cs

@@ -15,13 +15,14 @@ public void OnActionExecuted(ActionExecutedContext context)
             if (context.Exception is WebDriverResponseException exception)
             {
                 var logger = context.HttpContext.RequestServices.GetRequiredService<ILogger<WebDriverResponseExceptionFilter>>();
-                logger.LogError(exception, "Returning WebDriver error response with error code {ErrorCode}", exception.ErrorCode);
+                logger.LogError(exception, "Returning WebDriver error response with error code '{ErrorCode}'", exception.ErrorCode);
 
-                context.Result = new ObjectResult(new ResponseWithValue<ErrorResponse>(new ErrorResponse { ErrorCode = exception.ErrorCode, Message = exception.Message })) {
+                context.Result = new ObjectResult(new ResponseWithValue<ErrorResponse>(new ErrorResponse { ErrorCode = exception.ErrorCode, Message = exception.Message }))
+                {
                     StatusCode = exception.StatusCode
                 };
                 context.ExceptionHandled = true;
             }
         }
     }
-}
+}

src/FlaUI.WebDriver/WebDriverResponseException.cs

@@ -24,5 +24,7 @@ private WebDriverResponseException(string message, string errorCode, int statusC
         public static WebDriverResponseException WindowNotFoundByHandle(string windowHandle) => new WebDriverResponseException($"No window found with handle '{windowHandle}'", "no such window", 404);
 
         public static WebDriverResponseException NoWindowsOpenForSession() => new WebDriverResponseException($"No windows are open for the current session", "no such window", 404);
+
+        public static WebDriverResponseException Timeout(string message) => new WebDriverResponseException($"Timeout: ${message}", "timeout", 500);
     }
 }