Ladybird+LibJS: Add optional logging of *all* JS exceptions

When running with --log-all-js-exceptions, we will print the message
and backtrace for every single JS exception that is thrown, not just
the ones nobody caught.

This can sometimes be very helpful in debugging sites that swallow
important exceptions.

Ladybird/AppKit/main.mm

@@ -47,6 +47,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     StringView webdriver_content_ipc_path;
     bool use_gpu_painting = false;
     bool debug_web_content = false;
+    bool log_all_js_exceptions = false;
 
     Core::ArgsParser args_parser;
     args_parser.set_general_help("The Ladybird web browser");
@@ -55,6 +56,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     args_parser.add_option(use_gpu_painting, "Enable GPU painting", "enable-gpu-painting", 0);
     args_parser.add_option(debug_web_content, "Wait for debugger to attach to WebContent", "debug-web-content", 0);
     args_parser.add_option(certificates, "Path to a certificate file", "certificate", 'C', "certificate");
+    args_parser.add_option(log_all_js_exceptions, "Log all JavaScript exceptions", "log-all-js-exceptions", 0);
     args_parser.parse(arguments);
 
     WebView::ProcessManager::initialize();
@@ -89,6 +91,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         .enable_gpu_painting = use_gpu_painting ? Ladybird::EnableGPUPainting::Yes : Ladybird::EnableGPUPainting::No,
         .use_lagom_networking = Ladybird::UseLagomNetworking::Yes,
         .wait_for_debugger = debug_web_content ? Ladybird::WaitForDebugger::Yes : Ladybird::WaitForDebugger::No,
+        .log_all_js_exceptions = log_all_js_exceptions ? Ladybird::LogAllJSExceptions::Yes : Ladybird::LogAllJSExceptions::No,
     };
 
     auto* delegate = [[ApplicationDelegate alloc] init:move(initial_urls)

Ladybird/HelperProcess.cpp

@@ -65,6 +65,8 @@ ErrorOr<NonnullRefPtr<WebView::WebContentClient>> launch_web_content_process(
                 arguments.append("--use-gpu-painting"sv);
             if (web_content_options.wait_for_debugger == Ladybird::WaitForDebugger::Yes)
                 arguments.append("--wait-for-debugger"sv);
+            if (web_content_options.log_all_js_exceptions == Ladybird::LogAllJSExceptions::Yes)
+                arguments.append("--log-all-js-exceptions"sv);
             if (auto server = mach_server_name(); server.has_value()) {
                 arguments.append("--mach-server-name"sv);
                 arguments.append(server.value());

Ladybird/Qt/main.cpp

@@ -116,6 +116,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     bool enable_qt_networking = false;
     bool use_gpu_painting = false;
     bool debug_web_content = false;
+    bool log_all_js_exceptions = false;
 
     Core::ArgsParser args_parser;
     args_parser.set_general_help("The Ladybird web browser :^)");
@@ -127,6 +128,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     args_parser.add_option(use_gpu_painting, "Enable GPU painting", "enable-gpu-painting", 0);
     args_parser.add_option(debug_web_content, "Wait for debugger to attach to WebContent", "debug-web-content", 0);
     args_parser.add_option(certificates, "Path to a certificate file", "certificate", 'C', "certificate");
+    args_parser.add_option(log_all_js_exceptions, "Log all JavaScript exceptions", "log-all-js-exceptions", 0);
     args_parser.parse(arguments);
 
     WebView::ProcessManager::initialize();
@@ -170,6 +172,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         .enable_gpu_painting = use_gpu_painting ? Ladybird::EnableGPUPainting::Yes : Ladybird::EnableGPUPainting::No,
         .use_lagom_networking = enable_qt_networking ? Ladybird::UseLagomNetworking::No : Ladybird::UseLagomNetworking::Yes,
         .wait_for_debugger = debug_web_content ? Ladybird::WaitForDebugger::Yes : Ladybird::WaitForDebugger::No,
+        .log_all_js_exceptions = log_all_js_exceptions ? Ladybird::LogAllJSExceptions::Yes : Ladybird::LogAllJSExceptions::No,
     };
 
     Ladybird::BrowserWindow window(initial_urls, cookie_jar, web_content_options, webdriver_content_ipc_path);

Ladybird/Types.h

@@ -35,6 +35,11 @@ enum class WaitForDebugger {
     Yes
 };
 
+enum class LogAllJSExceptions {
+    No,
+    Yes
+};
+
 struct WebContentOptions {
     String command_line;
     String executable_path;
@@ -44,6 +49,7 @@ struct WebContentOptions {
     IsLayoutTestMode is_layout_test_mode { IsLayoutTestMode::No };
     UseLagomNetworking use_lagom_networking { UseLagomNetworking::No };
     WaitForDebugger wait_for_debugger { WaitForDebugger::No };
+    LogAllJSExceptions log_all_js_exceptions { LogAllJSExceptions::No };
 };
 
 }

Ladybird/WebContent/main.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020-2023, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2020-2024, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -53,6 +53,10 @@ static ErrorOr<void> load_content_filters();
 static ErrorOr<void> load_autoplay_allowlist();
 static ErrorOr<void> initialize_lagom_networking(Vector<ByteString> const& certificates);
 
+namespace JS {
+extern bool g_log_all_js_exceptions;
+}
+
 ErrorOr<int> serenity_main(Main::Arguments arguments)
 {
     AK::set_rich_debug_enabled(true);
@@ -89,6 +93,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     bool use_lagom_networking = false;
     bool use_gpu_painting = false;
     bool wait_for_debugger = false;
+    bool log_all_js_exceptions = false;
 
     Core::ArgsParser args_parser;
     args_parser.add_option(command_line, "Chrome process command line", "command-line", 0, "command_line");
@@ -100,6 +105,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     args_parser.add_option(use_gpu_painting, "Enable GPU painting", "use-gpu-painting", 0);
     args_parser.add_option(wait_for_debugger, "Wait for debugger", "wait-for-debugger", 0);
     args_parser.add_option(mach_server_name, "Mach server name", "mach-server-name", 0, "mach_server_name");
+    args_parser.add_option(log_all_js_exceptions, "Log all JavaScript exceptions", "log-all-js-exceptions", 0);
 
     args_parser.parse(arguments);
 
@@ -134,6 +140,10 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     TRY(Web::Bindings::initialize_main_thread_vm());
 
+    if (log_all_js_exceptions) {
+        JS::g_log_all_js_exceptions = true;
+    }
+
     auto maybe_content_filter_error = load_content_filters();
     if (maybe_content_filter_error.is_error())
         dbgln("Failed to load content filters: {}", maybe_content_filter_error.error());

Userland/Libraries/LibJS/Runtime/Completion.cpp

@@ -16,6 +16,8 @@
 
 namespace JS {
 
+bool g_log_all_js_exceptions = false;
+
 Completion::Completion(ThrowCompletionOr<Value> const& throw_completion_or_value)
 {
     if (throw_completion_or_value.is_throw_completion()) {
@@ -122,9 +124,25 @@ ThrowCompletionOr<Value> await(VM& vm, Value value)
     return throw_completion(result);
 }
 
+static void log_exception(Value value)
+{
+    if (!value.is_object()) {
+        dbgln("\033[31;1mTHROW!\033[0m {}", value);
+        return;
+    }
+
+    auto& object = value.as_object();
+    auto& vm = object.vm();
+    dbgln("\033[31;1mTHROW!\033[0m {}", object.get(vm.names.message).value());
+    vm.dump_backtrace();
+}
+
 // 6.2.4.2 ThrowCompletion ( value ), https://tc39.es/ecma262/#sec-throwcompletion
 Completion throw_completion(Value value)
 {
+    if (g_log_all_js_exceptions)
+        log_exception(value);
+
     // 1. Return Completion Record { [[Type]]: throw, [[Value]]: value, [[Target]]: empty }.
     return { Completion::Type::Throw, value, {} };
 }