webdriver: Implement support for simple dialogs (#37913)

Implement webdriver user prompt: accept alert, dismiss alert, get alert
text.

Tests:
https://github.com/longvatrong111/servo/actions/runs/16175408035
https://github.com/longvatrong111/servo/actions/runs/16175409545

Signed-off-by: batu_hoang <longvatrong111@gmail.com>

components/webdriver_server/user_prompt.rs

@@ -0,0 +1,93 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use embedder_traits::{WebDriverCommandMsg, WebDriverUserPromptAction};
+use ipc_channel::ipc;
+use webdriver::error::{ErrorStatus, WebDriverError, WebDriverResult};
+use webdriver::response::{ValueResponse, WebDriverResponse};
+
+use crate::{Handler, wait_for_script_response};
+
+impl Handler {
+    /// <https://w3c.github.io/webdriver/#dismiss-alert>
+    pub(crate) fn handle_dismiss_alert(&mut self) -> WebDriverResult<WebDriverResponse> {
+        // Step 1. If session's current top-level browsing context is no longer open,
+        // return error with error code no such window.
+        self.verify_top_level_browsing_context_is_open(self.session()?.webview_id)?;
+
+        // Step 3. Dismiss the current user prompt.
+        let (sender, receiver) = ipc::channel().unwrap();
+        self.send_message_to_embedder(WebDriverCommandMsg::HandleUserPrompt(
+            self.verified_webview_id(),
+            WebDriverUserPromptAction::Dismiss,
+            sender,
+        ))?;
+
+        match wait_for_script_response(receiver)? {
+            // Step 2. If the current user prompt is null, return error with error code no such alert.
+            Err(()) => Err(WebDriverError::new(
+                ErrorStatus::NoSuchAlert,
+                "No user prompt is currently active.",
+            )),
+            // Step 4. Return success with data null.
+            Ok(()) => Ok(WebDriverResponse::Void),
+        }
+    }
+
+    /// <https://w3c.github.io/webdriver/#accept-alert>
+    pub(crate) fn handle_accept_alert(&mut self) -> WebDriverResult<WebDriverResponse> {
+        // Step 1. If session's current top-level browsing context is no longer open,
+        // return error with error code no such window.
+        self.verify_top_level_browsing_context_is_open(self.session()?.webview_id)?;
+
+        // Step 3. Accept the current user prompt.
+        let (sender, receiver) = ipc::channel().unwrap();
+        self.send_message_to_embedder(WebDriverCommandMsg::HandleUserPrompt(
+            self.verified_webview_id(),
+            WebDriverUserPromptAction::Accept,
+            sender,
+        ))?;
+
+        match wait_for_script_response(receiver)? {
+            // Step 2. If the current user prompt is null, return error with error code no such alert.
+            Err(()) => Err(WebDriverError::new(
+                ErrorStatus::NoSuchAlert,
+                "No user prompt is currently active.",
+            )),
+            // Step 4. Return success with data null.
+            Ok(()) => Ok(WebDriverResponse::Void),
+        }
+    }
+
+    pub(crate) fn handle_get_alert_text(&mut self) -> WebDriverResult<WebDriverResponse> {
+        // Step 1. If session's current top-level browsing context is no longer open,
+        // return error with error code no such window.
+        self.verify_top_level_browsing_context_is_open(self.session()?.webview_id)?;
+
+        let (sender, receiver) = ipc::channel().unwrap();
+        self.send_message_to_embedder(WebDriverCommandMsg::GetAlertText(
+            self.verified_webview_id(),
+            sender,
+        ))?;
+
+        match wait_for_script_response(receiver)? {
+            // Step 2. If the current user prompt is null, return error with error code no such alert.
+            Err(()) => Err(WebDriverError::new(
+                ErrorStatus::NoSuchAlert,
+                "No user prompt is currently active.",
+            )),
+            // Step 3. Let message be the text message associated with the current user prompt
+            // or otherwise be null
+            // Step 4. Return success with data message.
+            Ok(message) => Ok(WebDriverResponse::Generic(ValueResponse(
+                serde_json::to_value(message).map_err(|e| {
+                    WebDriverError::new(
+                        ErrorStatus::UnknownError,
+                        format!("Failed to serialize alert text: {}", e),
+                    )
+                })?,
+            ))),
+        }
+    }
+}