webdriver: Keep constellation alive and Open new top-level browsing context with new session request when none is open (#37410)

Keep Constellation alive even when all browsing context closed in
WebDriver mode. In this case, when creating a new session, we would open
a new top-level browsing context.

Fixes: #37408
Testing: `./mach test-wpt -r
.\tests\wpt\tests\webdriver\tests\classic\close_window\close.py
--product servodriver`

---------

Signed-off-by: Euclid Ye <yezhizhenjiakang@gmail.com>
Signed-off-by: Euclid Ye <euclid.ye@huawei.com>

components/shared/embedder/webdriver.rs

@@ -146,17 +146,16 @@ pub enum WebDriverCommandMsg {
         Option<Rect<f32, CSSPixel>>,
         IpcSender<Option<RasterImage>>,
     ),
-    /// Create a new webview that loads about:blank. The constellation will use
+    /// Create a new webview that loads about:blank. The embedder will use
     /// the provided channels to return the top level browsing context id
-    /// associated with the new webview, and a notification when the initial
-    /// load is complete.
-    NewWebView(IpcSender<WebViewId>, IpcSender<WebDriverLoadStatus>),
+    /// associated with the new webview, and sets a "load status sender" if provided.
+    NewWebView(IpcSender<WebViewId>, Option<IpcSender<WebDriverLoadStatus>>),
     /// Close the webview associated with the provided id.
     CloseWebView(WebViewId),
     /// Focus the webview associated with the provided id.
     /// Sends back a bool indicating whether the focus was successfully set.
     FocusWebView(WebViewId, IpcSender<bool>),
-    /// Get focused webview.
+    /// Get focused webview. For now, this is only used when start new session.
     GetFocusedWebView(IpcSender<Option<WebViewId>>),
     /// Check whether top-level browsing context is open.
     IsWebViewOpen(WebViewId, IpcSender<bool>),

components/webdriver_server/lib.rs

@@ -504,17 +504,11 @@ impl Handler {
         self.session().unwrap().webview_id
     }
 
-    fn focus_webview_id(&self) -> WebDriverResult<WebViewId> {
+    fn focused_webview_id(&self) -> WebDriverResult<Option<WebViewId>> {
         let (sender, receiver) = ipc::channel().unwrap();
         self.send_message_to_embedder(WebDriverCommandMsg::GetFocusedWebView(sender.clone()))?;
         // Wait until the document is ready before returning the top-level browsing context id.
-        match wait_for_script_response(receiver)? {
-            Some(webview_id) => Ok(webview_id),
-            None => Err(WebDriverError::new(
-                ErrorStatus::NoSuchWindow,
-                "No focused webview found",
-            )),
-        }
+        wait_for_script_response(receiver)
     }
 
     fn session(&self) -> WebDriverResult<&WebDriverSession> {
@@ -578,8 +572,22 @@ impl Handler {
 
         // Step 6. Create a session
         // Step 8. Set session' current top-level browsing context
-        let webview_id = self.focus_webview_id()?;
+        let webview_id = match self.focused_webview_id()? {
+            Some(webview_id) => webview_id,
+            None => {
+                // This happens when there is no open webview.
+                // We need to create a new one. See https://github.com/servo/servo/issues/37408
+                let (sender, receiver) = ipc::channel().unwrap();
+                self.send_message_to_embedder(WebDriverCommandMsg::NewWebView(sender, None))?;
+                let webview_id = receiver
+                    .recv()
+                    .expect("IPC failure when creating new webview for new session");
+                self.focus_webview(webview_id)?;
+                webview_id
+            },
+        };
         let browsing_context_id = BrowsingContextId::from(webview_id);
+
         // Create and append session to the handler
         let session_id = self.create_session(
             &mut capabilities,
@@ -1085,7 +1093,8 @@ impl Handler {
         // Step 3. Handle any user prompt.
         self.handle_any_user_prompts(session.webview_id)?;
 
-        let cmd_msg = WebDriverCommandMsg::NewWebView(sender, self.load_status_sender.clone());
+        let cmd_msg =
+            WebDriverCommandMsg::NewWebView(sender, Some(self.load_status_sender.clone()));
         // Step 5. Create a new top-level browsing context by running the window open steps.
         // This MUST be done without invoking the focusing steps.
         self.send_message_to_embedder(cmd_msg)?;
@@ -1189,14 +1198,7 @@ impl Handler {
             let webview_id = *webview_id;
             session.webview_id = webview_id;
             session.browsing_context_id = BrowsingContextId::from(webview_id);
-            let (sender, receiver) = ipc::channel().unwrap();
-            let msg = WebDriverCommandMsg::FocusWebView(webview_id, sender);
-            self.send_message_to_embedder(msg)?;
-            if wait_for_script_response(receiver)? {
-                debug!("Focus new webview successfully");
-            } else {
-                debug!("Focus new webview failed, it may not exist anymore");
-            }
+            self.focus_webview(webview_id)?;
             Ok(WebDriverResponse::Void)
         } else {
             Err(WebDriverError::new(
@@ -2387,6 +2389,17 @@ impl Handler {
             Ok(())
         }
     }
+
+    fn focus_webview(&self, webview_id: WebViewId) -> Result<(), WebDriverError> {
+        let (sender, receiver) = ipc::channel().unwrap();
+        self.send_message_to_embedder(WebDriverCommandMsg::FocusWebView(webview_id, sender))?;
+        if wait_for_script_response(receiver)? {
+            debug!("Focus new webview successfully");
+        } else {
+            debug!("Focus new webview failed, it may not exist anymore");
+        }
+        Ok(())
+    }
 }
 
 impl WebDriverHandler<ServoExtensionRoute> for Handler {

ports/servoshell/desktop/app.rs

@@ -369,8 +369,9 @@ impl App {
                     if let Err(error) = response_sender.send(new_webview.id()) {
                         warn!("Failed to send response of NewWebview: {error}");
                     }
-
-                    running_state.set_load_status_sender(new_webview.id(), load_status_sender);
+                    if let Some(load_status_sender) = load_status_sender {
+                        running_state.set_load_status_sender(new_webview.id(), load_status_sender);
+                    }
                 },
                 WebDriverCommandMsg::CloseWebView(webview_id) => {
                     running_state.close_webview(webview_id);
@@ -446,8 +447,10 @@ impl App {
                         warn!("Failed to send response of GetViewportSize: {error}");
                     }
                 },
+                // This is only received when start new session.
                 WebDriverCommandMsg::GetFocusedWebView(sender) => {
                     let focused_webview = running_state.focused_webview();
+
                     if let Err(error) = sender.send(focused_webview.map(|w| w.id())) {
                         warn!("Failed to send response of GetFocusedWebView: {error}");
                     };

ports/servoshell/desktop/app_state.rs

@@ -272,7 +272,13 @@ impl RunningAppState {
             Some(last_created_webview) => {
                 last_created_webview.focus();
             },
-            None => self.servo.start_shutting_down(),
+            None if self.servoshell_preferences.webdriver_port.is_none() => {
+                self.servo.start_shutting_down()
+            },
+            None => {
+                // For WebDriver, don't shut down when last webview closed
+                // https://github.com/servo/servo/issues/37408
+            },
         }
     }
 

tests/wpt/meta/webdriver/tests/classic/accept_alert/accept.py.ini

@@ -12,7 +12,7 @@
     expected: FAIL
 
   [test_accept_prompt]
-    expected: ERROR
+    expected: FAIL
 
   [test_accept_in_popup_window]
     expected: FAIL

tests/wpt/meta/webdriver/tests/classic/close_window/close.py.ini

@@ -1,6 +1,3 @@
 [close.py]
   [test_close_last_browsing_context]
     expected: FAIL
-
-  [test_element_usage_after_closing_browsing_context]
-    expected: ERROR

tests/wpt/meta/webdriver/tests/classic/dismiss_alert/dismiss.py.ini

@@ -2,12 +2,6 @@
   [test_no_top_browsing_context]
     expected: ERROR
 
-  [test_no_browsing_context]
-    expected: ERROR
-
-  [test_dismiss_alert]
-    expected: FAIL
-
   [test_dismiss_confirm]
     expected: FAIL
 

tests/wpt/meta/webdriver/tests/classic/element_send_keys/file_upload.py.ini

@@ -8,11 +8,8 @@
   [test_single_file_appends_with_multiple_attribute]
     expected: FAIL
 
-  [test_focused]
-    expected: ERROR
-
   [test_strict_hidden]
-    expected: ERROR
+    expected: FAIL
 
   [test_strict_display_none]
-    expected: ERROR
+    expected: FAIL