AK+Everywhere: Remove the null state of DeprecatedString

This commit removes DeprecatedString's "null" state, and replaces all
its users with one of the following:
- A normal, empty DeprecatedString
- Optional<DeprecatedString>

Note that null states of DeprecatedFlyString/StringView/etc are *not*
affected by this commit. However, DeprecatedString::empty() is now
considered equal to a null StringView.

Userland/Utilities/ini.cpp

@@ -17,7 +17,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     StringView path;
     DeprecatedString group;
     DeprecatedString key;
-    DeprecatedString value_to_write;
+    StringView value_to_write;
 
     Core::ArgsParser args_parser;
     args_parser.add_positional_argument(path, "Path to INI file", "path");

Userland/Utilities/ls.cpp

@@ -248,15 +248,15 @@ static int print_escaped(StringView name)
 
 static DeprecatedString& hostname()
 {
-    static DeprecatedString s_hostname;
-    if (s_hostname.is_null()) {
+    static Optional<DeprecatedString> s_hostname;
+    if (!s_hostname.has_value()) {
         char buffer[HOST_NAME_MAX];
         if (gethostname(buffer, sizeof(buffer)) == 0)
             s_hostname = buffer;
         else
             s_hostname = "localhost";
     }
-    return s_hostname;
+    return *s_hostname;
 }
 
 static size_t print_name(const struct stat& st, DeprecatedString const& name, Optional<StringView> path_for_link_resolution, StringView path_for_hyperlink)
@@ -470,7 +470,6 @@ static int do_file_system_object_long(DeprecatedString const& path)
         builder.append('/');
         builder.append(metadata.name);
         metadata.path = builder.to_deprecated_string();
-        VERIFY(!metadata.path.is_null());
         int rc = lstat(metadata.path.characters(), &metadata.stat);
         if (rc < 0)
             perror("lstat");
@@ -595,7 +594,6 @@ int do_file_system_object_short(DeprecatedString const& path)
         builder.append('/');
         builder.append(metadata.name);
         metadata.path = builder.to_deprecated_string();
-        VERIFY(!metadata.path.is_null());
         int rc = lstat(metadata.path.characters(), &metadata.stat);
         if (rc < 0)
             perror("lstat");

Userland/Utilities/markdown-check.cpp

@@ -179,10 +179,11 @@ RecursionDecision MarkdownLinkage::visit(Markdown::Heading const& heading)
 RecursionDecision MarkdownLinkage::visit(Markdown::Text::LinkNode const& link_node)
 {
     DeprecatedString const& href = link_node.href;
-    if (href.is_null()) {
+    if (href.is_empty()) {
         // Nothing to do here.
         return RecursionDecision::Recurse;
     }
+
     auto url = URL::create_with_url_or_path(href);
     if (url.is_valid()) {
         if (url.scheme() == "https" || url.scheme() == "http") {

Userland/Utilities/mktemp.cpp

@@ -30,7 +30,7 @@ static DeprecatedString generate_random_filename(DeprecatedString const& pattern
     return new_filename.to_deprecated_string();
 }
 
-static ErrorOr<DeprecatedString> make_temp(DeprecatedString const& pattern, bool directory, bool dry_run)
+static ErrorOr<Optional<DeprecatedString>> make_temp(DeprecatedString const& pattern, bool directory, bool dry_run)
 {
     for (int i = 0; i < 100; ++i) {
         auto path = generate_random_filename(pattern);
@@ -49,7 +49,7 @@ static ErrorOr<DeprecatedString> make_temp(DeprecatedString const& pattern, bool
             }
         }
     }
-    return DeprecatedString {};
+    return OptionalNone {};
 }
 
 ErrorOr<int> serenity_main(Main::Arguments arguments)
@@ -100,7 +100,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     auto target_path = LexicalPath::join(final_target_directory->to_deprecated_string(), final_file_template->to_deprecated_string()).string();
 
     auto final_path = TRY(make_temp(target_path, create_directory, dry_run));
-    if (final_path.is_null()) {
+    if (!final_path.has_value()) {
         if (!quiet) {
             if (create_directory)
                 warnln("Failed to create directory via template {}", target_path.characters());
@@ -110,7 +110,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         return 1;
     }
 
-    outln("{}", final_path);
+    outln("{}", *final_path);
 
     return 0;
 }

Userland/Utilities/paste.cpp

@@ -72,7 +72,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         clipboard.on_change = [&](DeprecatedString const&) {
             // Technically there's a race here...
             auto data_and_type = clipboard.fetch_data_and_type();
-            if (data_and_type.mime_type.is_null()) {
+            if (data_and_type.mime_type.is_empty()) {
                 spawn_command(watch_command, {}, "clear");
             } else {
                 spawn_command(watch_command, data_and_type.data, "data");
@@ -87,7 +87,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     auto data_and_type = clipboard.fetch_data_and_type();
 
-    if (data_and_type.mime_type.is_null()) {
+    if (data_and_type.mime_type.is_empty()) {
         warnln("Nothing copied");
         return 1;
     }

Userland/Utilities/su.cpp

@@ -18,7 +18,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     StringView first_positional;
     StringView second_positional;
-    DeprecatedString command;
+    StringView command;
     bool simulate_login = false;
 
     Core::ArgsParser args_parser;
@@ -65,7 +65,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     if (command.is_null()) {
         TRY(Core::System::exec(account.shell(), Array<StringView, 1> { account.shell().view() }, Core::System::SearchInPath::No));
     } else {
-        TRY(Core::System::exec(account.shell(), Array<StringView, 3> { account.shell().view(), "-c"sv, command.view() }, Core::System::SearchInPath::No));
+        TRY(Core::System::exec(account.shell(), Array<StringView, 3> { account.shell().view(), "-c"sv, command }, Core::System::SearchInPath::No));
     }
 
     return 1;

Userland/Utilities/sysctl.cpp

@@ -12,7 +12,7 @@
 
 static bool s_set_variable = false;
 
-static DeprecatedString get_variable(StringView name)
+static Optional<DeprecatedString> get_variable(StringView name)
 {
     auto path = DeprecatedString::formatted("/sys/kernel/conf/{}", name);
     auto file = Core::File::open(path, Core::File::OpenMode::Read);
@@ -25,22 +25,22 @@ static DeprecatedString get_variable(StringView name)
         warnln("Failed to read {}: {}", path, buffer.error());
         return {};
     }
-    return { (char const*)buffer.value().data(), buffer.value().size(), Chomp };
+    return DeprecatedString { (char const*)buffer.value().data(), buffer.value().size(), Chomp };
 }
 
 static bool read_variable(StringView name)
 {
     auto value = get_variable(name);
-    if (value.is_null())
+    if (!value.has_value())
         return false;
-    outln("{} = {}", name, value);
+    outln("{} = {}", name, *value);
     return true;
 }
 
 static bool write_variable(StringView name, StringView value)
 {
     auto old_value = get_variable(name);
-    if (old_value.is_null())
+    if (!old_value.has_value())
         return false;
     auto path = DeprecatedString::formatted("/sys/kernel/conf/{}", name);
     auto file = Core::File::open(path, Core::File::OpenMode::Write);
@@ -52,7 +52,7 @@ static bool write_variable(StringView name, StringView value)
         warnln("Failed to write {}: {}", path, result.error());
         return false;
     }
-    outln("{}: {} -> {}", name, old_value, value);
+    outln("{}: {} -> {}", name, *old_value, value);
     return true;
 }
 

Userland/Utilities/wallpaper.cpp

@@ -22,7 +22,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     bool show_all = false;
     bool show_current = false;
     bool set_random = false;
-    DeprecatedString path;
+    StringView path;
 
     Core::ArgsParser args_parser;
     args_parser.add_option(show_all, "Show all wallpapers", "show-all", 'a');