From 1e3622432107dc5b47242da88479e0c189e7a488 Mon Sep 17 00:00:00 2001
From: Luke Wilde <lukew@serenityos.org>
Date: Mon, 27 Jun 2022 19:53:22 +0100
Subject: [PATCH] LibWeb: Print unhandled rejections the same way as unhandled
 exceptions

---
 .../LibWeb/HTML/Scripting/Environments.cpp    |  3 ++-
 .../HTML/Scripting/ExceptionReporter.cpp      | 26 +++++++++++--------
 .../LibWeb/HTML/Scripting/ExceptionReporter.h |  6 +++++
 3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/Userland/Libraries/LibWeb/HTML/Scripting/Environments.cpp b/Userland/Libraries/LibWeb/HTML/Scripting/Environments.cpp
index 23abf2c1f8..da1945f979 100644
--- a/Userland/Libraries/LibWeb/HTML/Scripting/Environments.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Scripting/Environments.cpp
@@ -10,6 +10,7 @@
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/HTML/PromiseRejectionEvent.h>
 #include <LibWeb/HTML/Scripting/Environments.h>
+#include <LibWeb/HTML/Scripting/ExceptionReporter.h>
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/Page/Page.h>
 
@@ -232,7 +233,7 @@ void EnvironmentSettingsObject::notify_about_rejected_promises(Badge<EventLoop>)
             // This algorithm results in promise rejections being marked as handled or not handled. These concepts parallel handled and not handled script errors.
             // If a rejection is still not handled after this, then the rejection may be reported to a developer console.
             if (not_handled)
-                dbgln("WARNING: A promise was rejected without any handlers. promise={:p}, result={}", &promise, promise.result().to_string_without_side_effects());
+                HTML::print_error_from_value(promise.result(), ErrorInPromise::Yes);
         }
     });
 }
diff --git a/Userland/Libraries/LibWeb/HTML/Scripting/ExceptionReporter.cpp b/Userland/Libraries/LibWeb/HTML/Scripting/ExceptionReporter.cpp
index c5e4802cdd..bea5fbc44b 100644
--- a/Userland/Libraries/LibWeb/HTML/Scripting/ExceptionReporter.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Scripting/ExceptionReporter.cpp
@@ -11,24 +11,19 @@
 
 namespace Web::HTML {
 
-// https://html.spec.whatwg.org/#report-the-exception
-void report_exception(JS::Completion const& throw_completion)
+void print_error_from_value(JS::Value value, ErrorInPromise error_in_promise)
 {
-    // FIXME: This is just old code, and does not strictly follow the spec of report an exception.
     // FIXME: We should probably also report these exceptions to the JS console.
-    VERIFY(throw_completion.type() == JS::Completion::Type::Throw);
-    VERIFY(throw_completion.value().has_value());
-    auto thrown_value = *throw_completion.value();
-    if (thrown_value.is_object()) {
-        auto& object = thrown_value.as_object();
+    if (value.is_object()) {
+        auto& object = value.as_object();
         auto& vm = object.vm();
         auto name = object.get_without_side_effects(vm.names.name).value_or(JS::js_undefined());
         auto message = object.get_without_side_effects(vm.names.message).value_or(JS::js_undefined());
         if (name.is_accessor() || message.is_accessor()) {
             // The result is not going to be useful, let's just print the value. This affects DOMExceptions, for example.
-            dbgln("\033[31;1mUnhandled JavaScript exception:\033[0m {}", thrown_value);
+            dbgln("\033[31;1mUnhandled JavaScript exception{}:\033[0m {}", error_in_promise == ErrorInPromise::Yes ? " (in promise)" : "", JS::Value(&object));
         } else {
-            dbgln("\033[31;1mUnhandled JavaScript exception:\033[0m [{}] {}", name, message);
+            dbgln("\033[31;1mUnhandled JavaScript exception{}:\033[0m [{}] {}", error_in_promise == ErrorInPromise::Yes ? " (in promise)" : "", name, message);
         }
         if (is<JS::Error>(object)) {
             auto const& error_value = static_cast<JS::Error const&>(object);
@@ -39,8 +34,17 @@ void report_exception(JS::Completion const& throw_completion)
             }
         }
     } else {
-        dbgln("\033[31;1mUnhandled JavaScript exception:\033[0m {}", thrown_value);
+        dbgln("\033[31;1mUnhandled JavaScript exception:\033[0m {}", value);
     }
 }
 
+// https://html.spec.whatwg.org/#report-the-exception
+void report_exception(JS::Completion const& throw_completion)
+{
+    // FIXME: This is just old code, and does not strictly follow the spec of report an exception.
+    VERIFY(throw_completion.type() == JS::Completion::Type::Throw);
+    VERIFY(throw_completion.value().has_value());
+    print_error_from_value(*throw_completion.value(), ErrorInPromise::No);
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/HTML/Scripting/ExceptionReporter.h b/Userland/Libraries/LibWeb/HTML/Scripting/ExceptionReporter.h
index dc4aad44c8..f7d7061772 100644
--- a/Userland/Libraries/LibWeb/HTML/Scripting/ExceptionReporter.h
+++ b/Userland/Libraries/LibWeb/HTML/Scripting/ExceptionReporter.h
@@ -10,6 +10,12 @@
 
 namespace Web::HTML {
 
+enum class ErrorInPromise {
+    No,
+    Yes,
+};
+
+void print_error_from_value(JS::Value, ErrorInPromise);
 void report_exception(JS::Completion const&);
 
 template<typename T>