WebDriver: Ensure that the session's current window handle is valid

After closing a window, it is the client's job to switch to another
window before executing any other command. Currently, we will crash if
that did not happen when we try to send an IPC to a window handle that
we no longer hold. This patch makes us return a "no such window" error
instead.

The exceptions to this new check are the "Switch to Window" and "Get
Window Handles" commands.

Userland/Services/WebDriver/Client.cpp

@@ -37,14 +37,18 @@ Client::Client(NonnullOwnPtr<Core::BufferedTCPSocket> socket, LaunchBrowserCallb
 
 Client::~Client() = default;
 
-ErrorOr<NonnullRefPtr<Session>, Web::WebDriver::Error> Client::find_session_with_id(StringView session_id)
+ErrorOr<NonnullRefPtr<Session>, Web::WebDriver::Error> Client::find_session_with_id(StringView session_id, AllowInvalidWindowHandle allow_invalid_window_handle)
 {
     auto session_id_or_error = session_id.to_number<unsigned>();
     if (!session_id_or_error.has_value())
         return Web::WebDriver::Error::from_code(Web::WebDriver::ErrorCode::InvalidSessionId, "Invalid session id");
 
-    if (auto session = s_sessions.get(*session_id_or_error); session.has_value())
+    if (auto session = s_sessions.get(*session_id_or_error); session.has_value()) {
+        if (allow_invalid_window_handle == AllowInvalidWindowHandle::No)
+            TRY(session.value()->ensure_current_window_handle_is_valid());
+
         return *session.release_value();
+    }
 
     return Web::WebDriver::Error::from_code(Web::WebDriver::ErrorCode::InvalidSessionId, "Invalid session id");
 }
@@ -311,7 +315,7 @@ Web::WebDriver::Response Client::close_window(Web::WebDriver::Parameters paramet
 Web::WebDriver::Response Client::switch_to_window(Web::WebDriver::Parameters parameters, AK::JsonValue payload)
 {
     dbgln_if(WEBDRIVER_DEBUG, "Handling POST /session/<session_id>/window");
-    auto session = TRY(find_session_with_id(parameters[0]));
+    auto session = TRY(find_session_with_id(parameters[0], AllowInvalidWindowHandle::Yes));
 
     if (!payload.is_object())
         return Web::WebDriver::Error::from_code(Web::WebDriver::ErrorCode::InvalidArgument, "Payload is not a JSON object");
@@ -331,7 +335,7 @@ Web::WebDriver::Response Client::switch_to_window(Web::WebDriver::Parameters par
 Web::WebDriver::Response Client::get_window_handles(Web::WebDriver::Parameters parameters, JsonValue)
 {
     dbgln_if(WEBDRIVER_DEBUG, "Handling GET /session/<session_id>/window/handles");
-    auto session = TRY(find_session_with_id(parameters[0]));
+    auto session = TRY(find_session_with_id(parameters[0], AllowInvalidWindowHandle::Yes));
     return session->get_window_handles();
 }
 

Userland/Services/WebDriver/Client.h

@@ -35,7 +35,11 @@ public:
 private:
     Client(NonnullOwnPtr<Core::BufferedTCPSocket>, LaunchBrowserCallbacks, Core::EventReceiver* parent);
 
-    ErrorOr<NonnullRefPtr<Session>, Web::WebDriver::Error> find_session_with_id(StringView session_id);
+    enum class AllowInvalidWindowHandle {
+        No,
+        Yes,
+    };
+    ErrorOr<NonnullRefPtr<Session>, Web::WebDriver::Error> find_session_with_id(StringView session_id, AllowInvalidWindowHandle = AllowInvalidWindowHandle::No);
 
     virtual Web::WebDriver::Response new_session(Web::WebDriver::Parameters parameters, JsonValue payload) override;
     virtual Web::WebDriver::Response delete_session(Web::WebDriver::Parameters parameters, JsonValue payload) override;

Userland/Services/WebDriver/Session.cpp

@@ -169,6 +169,13 @@ Web::WebDriver::Response Session::get_window_handles() const
     return JsonValue { move(handles) };
 }
 
+ErrorOr<void, Web::WebDriver::Error> Session::ensure_current_window_handle_is_valid() const
+{
+    if (auto current_window = m_windows.get(m_current_window_handle); current_window.has_value())
+        return {};
+    return Web::WebDriver::Error::from_code(Web::WebDriver::ErrorCode::NoSuchWindow, "Window not found"sv);
+}
+
 Web::WebDriver::Response Session::execute_script(JsonValue payload, ScriptMode mode) const
 {
     ScopeGuard guard { [&]() { web_content_connection().on_script_executed = nullptr; } };

Userland/Services/WebDriver/Session.h

@@ -53,6 +53,7 @@ public:
     Web::WebDriver::Response close_window();
     Web::WebDriver::Response switch_to_window(StringView);
     Web::WebDriver::Response get_window_handles() const;
+    ErrorOr<void, Web::WebDriver::Error> ensure_current_window_handle_is_valid() const;
 
     enum class ScriptMode {
         Sync,