AK: Serialize URL hosts with 'concept-host-serializer'

In order to follow spec text to achieve this, we need to change the
underlying representation of a host in AK::URL to deserialized format.
Before this, we were parsing the host and then immediately serializing
it again.

Making that change resulted in a whole bunch of fallout.

After this change, callers can access the serialized data through
this concept-host-serializer. The functional end result of this
change is that IPv6 hosts are now correctly serialized to be
surrounded with '[' and ']'.

Userland/Applications/Assistant/Providers.cpp

@@ -248,8 +248,8 @@ void URLProvider::query(DeprecatedString const& query, Function<void(Vector<Nonn
 
     if (url.scheme().is_empty())
         url.set_scheme("http");
-    if (url.host().is_empty())
-        url.set_host(query);
+    if (url.host().has<Empty>() || url.host() == String {})
+        url.set_host(String::from_deprecated_string(query).release_value_but_fixme_should_propagate_errors());
     if (url.path_segment_count() == 0)
         url.set_paths({ "" });
 

Userland/Applications/Browser/CookieJar.cpp

@@ -208,7 +208,10 @@ Optional<DeprecatedString> CookieJar::canonicalize_domain(const URL& url)
         return {};
 
     // FIXME: Implement RFC 5890 to "Convert each label that is not a Non-Reserved LDH (NR-LDH) label to an A-label".
-    return url.host().to_lowercase();
+    if (url.host().has<Empty>())
+        return {};
+
+    return url.serialized_host().release_value_but_fixme_should_propagate_errors().to_deprecated_string().to_lowercase();
 }
 
 bool CookieJar::domain_matches(DeprecatedString const& string, DeprecatedString const& domain_string)

Userland/Applications/Browser/Tab.cpp

@@ -107,10 +107,10 @@ void Tab::update_status(Optional<String> text_override, i32 count_waiting)
 
     if (count_waiting == 0) {
         // ex: "Loading google.com"
-        m_statusbar->set_text(String::formatted("Loading {}", m_navigating_url->host()).release_value_but_fixme_should_propagate_errors());
+        m_statusbar->set_text(String::formatted("Loading {}", m_navigating_url->serialized_host().release_value_but_fixme_should_propagate_errors()).release_value_but_fixme_should_propagate_errors());
     } else {
         // ex: "google.com is waiting on 5 resources"
-        m_statusbar->set_text(String::formatted("{} is waiting on {} resource{}", m_navigating_url->host(), count_waiting, count_waiting == 1 ? ""sv : "s"sv).release_value_but_fixme_should_propagate_errors());
+        m_statusbar->set_text(String::formatted("{} is waiting on {} resource{}", m_navigating_url->serialized_host().release_value_but_fixme_should_propagate_errors(), count_waiting, count_waiting == 1 ? ""sv : "s"sv).release_value_but_fixme_should_propagate_errors());
     }
 }
 

Userland/Applications/Spreadsheet/HelpWindow.cpp

@@ -83,7 +83,7 @@ HelpWindow::HelpWindow(GUI::Window* parent)
     m_webview = splitter.add<WebView::OutOfProcessWebView>();
     m_webview->on_link_click = [this](auto& url, auto&, auto&&) {
         VERIFY(url.scheme() == "spreadsheet");
-        if (url.host() == "example") {
+        if (url.host().template has<String>() && url.host().template get<String>() == "example"sv) {
             auto example_path = url.serialize_path();
             auto entry = LexicalPath::basename(example_path);
             auto doc_option = m_docs.get_object(entry);
@@ -122,11 +122,11 @@ HelpWindow::HelpWindow(GUI::Window* parent)
 
             widget->add_sheet(sheet.release_nonnull());
             window->show();
-        } else if (url.host() == "doc") {
+        } else if (url.host() == String::from_utf8_short_string("doc"sv)) {
             auto entry = LexicalPath::basename(url.serialize_path());
             m_webview->load(URL::create_with_data("text/html", render(entry)));
         } else {
-            dbgln("Invalid spreadsheet action domain '{}'", url.host());
+            dbgln("Invalid spreadsheet action domain '{}'", url.serialized_host().release_value_but_fixme_should_propagate_errors());
         }
     };
 

Userland/Applications/Spreadsheet/Spreadsheet.cpp

@@ -264,7 +264,7 @@ Optional<Position> Sheet::position_from_url(const URL& url) const
         return {};
     }
 
-    if (url.scheme() != "spreadsheet" || url.host() != "cell") {
+    if (url.scheme() != "spreadsheet" || url.host() != String::from_utf8_short_string("cell"sv)) {
         dbgln("Bad url: {}", url.to_deprecated_string());
         return {};
     }
@@ -757,7 +757,7 @@ URL Position::to_url(Sheet const& sheet) const
 {
     URL url;
     url.set_scheme("spreadsheet");
-    url.set_host("cell");
+    url.set_host(String::from_utf8_short_string("cell"sv));
     url.set_paths({ DeprecatedString::number(getpid()) });
     url.set_fragment(to_cell_identifier(sheet));
     return url;