LibWeb+WebDriver: Support running headless WebDriver sessions

This adds an "extension capability" for clients to indicate that a
headless browser should be used for the session.

Userland/Libraries/LibWeb/WebDriver/Capabilities.cpp

@@ -45,6 +45,27 @@ static Response deserialize_as_an_unhandled_prompt_behavior(JsonValue value)
     return value;
 }
 
+static Response deserialize_as_ladybird_options(JsonValue value)
+{
+    if (!value.is_object())
+        return Error::from_code(ErrorCode::InvalidArgument, "Extension capability serenity:ladybird must be an object"sv);
+
+    auto const& object = value.as_object();
+
+    if (auto const* headless = object.get_ptr("headless"sv); headless && !headless->is_bool())
+        return Error::from_code(ErrorCode::InvalidArgument, "Extension capability serenity:ladybird/headless must be a boolean"sv);
+
+    return value;
+}
+
+static JsonObject default_ladybird_options()
+{
+    JsonObject options;
+    options.set("headless"sv, false);
+
+    return options;
+}
+
 // https://w3c.github.io/webdriver/#dfn-validate-capabilities
 static ErrorOr<JsonObject, Error> validate_capabilities(JsonValue const& capability)
 {
@@ -118,8 +139,12 @@ static ErrorOr<JsonObject, Error> validate_capabilities(JsonValue const& capabil
 
         // FIXME: -> name is the name of an additional WebDriver capability
         // FIXME:     Let deserialized be the result of trying to run the additional capability deserialization algorithm for the extension capability corresponding to name, with argument value.
-        // FIXME: -> name is the key of an extension capability
-        // FIXME:     If name is known to the implementation, let deserialized be the result of trying to deserialize value in an implementation-specific way. Otherwise, let deserialized be set to value.
+
+        // -> name is the key of an extension capability
+        //     If name is known to the implementation, let deserialized be the result of trying to deserialize value in an implementation-specific way. Otherwise, let deserialized be set to value.
+        else if (name == "serenity:ladybird"sv) {
+            deserialized = TRY(deserialize_as_ladybird_options(value));
+        }
 
         // -> The remote end is an endpoint node
         else {
@@ -232,6 +257,7 @@ static JsonValue match_capabilities(JsonObject const& capabilities)
     matched_capabilities.set("setWindowRect"sv, true);
 
     // 2. Optionally add extension capabilities as entries to matched capabilities. The values of these may be elided, and there is no requirement that all extension capabilities be added.
+    matched_capabilities.set("serenity:ladybird"sv, default_ladybird_options());
 
     // 3. For each name and value corresponding to capability’s own properties:
     auto result = capabilities.try_for_each_member([&](auto const& name, auto const& value) -> ErrorOr<void> {
@@ -366,4 +392,15 @@ Response process_capabilities(JsonValue const& parameters)
     return JsonValue {};
 }
 
+LadybirdOptions::LadybirdOptions(JsonObject const& capabilities)
+{
+    auto const* options = capabilities.get_ptr("serenity:ladybird"sv);
+    if (!options || !options->is_object())
+        return;
+
+    auto const* headless = options->as_object().get_ptr("headless"sv);
+    if (headless && headless->is_bool())
+        this->headless = headless->as_bool();
+}
+
 }

Userland/Libraries/LibWeb/WebDriver/Capabilities.h

@@ -54,6 +54,12 @@ constexpr UnhandledPromptBehavior unhandled_prompt_behavior_from_string(StringVi
     VERIFY_NOT_REACHED();
 }
 
+struct LadybirdOptions {
+    explicit LadybirdOptions(JsonObject const& capabilities);
+
+    bool headless { false };
+};
+
 Response process_capabilities(JsonValue const& parameters);
 
 }

Userland/Services/WebDriver/Client.cpp

@@ -151,11 +151,11 @@ Web::WebDriver::Response Client::new_session(Web::WebDriver::Parameters, JsonVal
     auto session_id = Client::s_next_session_id++;
 
     // 7. Let session be a new session with the session ID of session id.
-    NonnullOwnPtr<Session> session = make<Session>(session_id, *this);
-    auto start_result = session->start();
-    if (start_result.is_error()) {
+    Web::WebDriver::LadybirdOptions options { capabilities.as_object() };
+    auto session = make<Session>(session_id, *this, move(options));
+
+    if (auto start_result = session->start(); start_result.is_error())
         return Web::WebDriver::Error::from_code(Web::WebDriver::ErrorCode::SessionNotCreated, String::formatted("Failed to start session: {}", start_result.error().string_literal()));
-    }
 
     auto& web_content_connection = session->web_content_connection();
 

Userland/Services/WebDriver/Session.cpp

@@ -17,8 +17,9 @@
 
 namespace WebDriver {
 
-Session::Session(unsigned session_id, NonnullRefPtr<Client> client)
+Session::Session(unsigned session_id, NonnullRefPtr<Client> client, Web::WebDriver::LadybirdOptions options)
     : m_client(move(client))
+    , m_options(move(options))
     , m_id(session_id)
 {
 }
@@ -63,6 +64,17 @@ ErrorOr<void> Session::start()
     auto web_content_socket_path = String::formatted("/tmp/webdriver/session_{}_{}", getpid(), m_id);
     auto web_content_server = TRY(create_server(web_content_socket_path, promise));
 
+    if (m_options.headless) {
+        char const* argv[] = {
+            "/bin/headless-browser",
+            "--webdriver-ipc-path",
+            web_content_socket_path.characters(),
+            "about:blank",
+            nullptr,
+        };
+
+        m_browser_pid = TRY(Core::System::posix_spawn("/bin/headless-browser"sv, nullptr, nullptr, const_cast<char**>(argv), environ));
+    } else {
         char const* argv[] = {
             "/bin/Browser",
             "--webdriver-content-path",
@@ -71,6 +83,7 @@ ErrorOr<void> Session::start()
         };
 
         m_browser_pid = TRY(Core::System::posix_spawn("/bin/Browser"sv, nullptr, nullptr, const_cast<char**>(argv), environ));
+    }
 
     // FIXME: Allow this to be more asynchronous. For now, this at least allows us to propagate
     //        errors received while accepting the Browser and WebContent sockets.

Userland/Services/WebDriver/Session.h

@@ -11,6 +11,7 @@
 #include <AK/Error.h>
 #include <AK/RefPtr.h>
 #include <LibCore/Promise.h>
+#include <LibWeb/WebDriver/Capabilities.h>
 #include <LibWeb/WebDriver/Error.h>
 #include <LibWeb/WebDriver/Response.h>
 #include <WebDriver/WebContentConnection.h>
@@ -20,7 +21,7 @@ namespace WebDriver {
 
 class Session {
 public:
-    Session(unsigned session_id, NonnullRefPtr<Client> client);
+    Session(unsigned session_id, NonnullRefPtr<Client> client, Web::WebDriver::LadybirdOptions options);
     ~Session();
 
     unsigned session_id() const { return m_id; }
@@ -39,8 +40,11 @@ private:
     ErrorOr<NonnullRefPtr<Core::LocalServer>> create_server(String const& socket_path, NonnullRefPtr<ServerPromise> promise);
 
     NonnullRefPtr<Client> m_client;
+    Web::WebDriver::LadybirdOptions m_options;
+
     bool m_started { false };
     unsigned m_id { 0 };
+
     RefPtr<WebContentConnection> m_web_content_connection;
     Optional<pid_t> m_browser_pid;
 };

Userland/Services/WebDriver/main.cpp

@@ -71,6 +71,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     outln("Listening on {}:{}", ipv4_address.value(), port);
 
     TRY(Core::System::unveil("/bin/Browser", "rx"));
+    TRY(Core::System::unveil("/bin/headless-browser", "rx"));
     TRY(Core::System::unveil("/etc/timezone", "r"));
     TRY(Core::System::unveil("/res/icons", "r"));
     TRY(Core::System::unveil("/tmp/webdriver", "rwc"));