LibJS+LibWeb: Add a custom host hook to log unparsed date strings

This lets us log when our Date.parse implementation was unable to handle
a string found on the web.

Userland/Libraries/LibJS/Runtime/DateConstructor.cpp

@@ -150,7 +150,7 @@ static double parse_simplified_iso8601(ByteString const& iso_8601)
     return time_clip(time_ms);
 }
 
-static double parse_date_string(ByteString const& date_string)
+static double parse_date_string(VM& vm, ByteString const& date_string)
 {
     auto value = parse_simplified_iso8601(date_string);
     if (isfinite(value))
@@ -188,6 +188,7 @@ static double parse_date_string(ByteString const& date_string)
             return 1000.0 * maybe_datetime->timestamp();
     }
 
+    vm.host_unrecognized_date_string(date_string);
     return NAN;
 }
 
@@ -257,7 +258,7 @@ ThrowCompletionOr<NonnullGCPtr<Object>> DateConstructor::construct(FunctionObjec
             if (primitive.is_string()) {
                 // 1. Assert: The next step never returns an abrupt completion because Type(v) is String.
                 // 2. Let tv be the result of parsing v as a date, in exactly the same manner as for the parse method (21.4.3.2).
-                time_value = parse_date_string(primitive.as_string().byte_string());
+                time_value = parse_date_string(vm, primitive.as_string().byte_string());
             }
             // iii. Else,
             else {
@@ -334,7 +335,7 @@ JS_DEFINE_NATIVE_FUNCTION(DateConstructor::parse)
 
     auto date_string = TRY(vm.argument(0).to_byte_string(vm));
 
-    return Value(parse_date_string(date_string));
+    return Value(parse_date_string(vm, date_string));
 }
 
 // 21.4.3.4 Date.UTC ( year [ , month [ , date [ , hours [ , minutes [ , seconds [ , ms ] ] ] ] ] ] ), https://tc39.es/ecma262/#sec-date.utc

Userland/Libraries/LibJS/Runtime/VM.cpp

@@ -164,6 +164,10 @@ VM::VM(OwnPtr<CustomData> custom_data, ErrorMessages error_messages)
 
         return HandledByHost::Handled;
     };
+
+    // AD-HOC: Inform the host that we received a date string we were unable to parse.
+    host_unrecognized_date_string = [](StringView) {
+    };
 }
 
 VM::~VM() = default;

Userland/Libraries/LibJS/Runtime/VM.h

@@ -274,6 +274,7 @@ public:
     Function<ThrowCompletionOr<void>(Realm&)> host_ensure_can_compile_strings;
     Function<ThrowCompletionOr<void>(Object&)> host_ensure_can_add_private_element;
     Function<ThrowCompletionOr<HandledByHost>(ArrayBuffer&, size_t)> host_resize_array_buffer;
+    Function<void(StringView)> host_unrecognized_date_string;
 
     Vector<StackTraceElement> stack_trace() const;
 

Userland/Libraries/LibWeb/Bindings/MainThreadVM.cpp

@@ -545,6 +545,10 @@ ErrorOr<void> initialize_main_thread_vm(HTML::EventLoop::Type type)
         HTML::fetch_single_imported_module_script(realm, url.release_value(), *fetch_client, destination, fetch_options, *settings_object, fetch_referrer, module_request, perform_fetch, on_single_fetch_complete);
     };
 
+    s_main_thread_vm->host_unrecognized_date_string = [](StringView date) {
+        dbgln("Unable to parse date string: \"{}\"", date);
+    };
+
     return {};
 }