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/DevTools/HackStudio/Debugger/BacktraceModel.cpp

@@ -47,7 +47,7 @@ Vector<BacktraceModel::FrameInfo> BacktraceModel::create_backtrace(Debug::Proces
         if (frame_index > 0)
             --current_instruction;
         DeprecatedString name = lib->debug_info->elf().symbolicate(current_instruction - lib->base_address);
-        if (name.is_null()) {
+        if (name.is_empty()) {
             dbgln("BacktraceModel: couldn't find containing function for address: {:p} (library={})", current_instruction, lib->name);
             name = "<missing>";
         }

Userland/DevTools/HackStudio/Debugger/Debugger.cpp

@@ -134,7 +134,7 @@ void Debugger::start()
 
 Debugger::CreateDebugSessionResult Debugger::create_debug_session()
 {
-    if (!m_executable_path.is_null()) {
+    if (!m_executable_path.is_empty()) {
         auto child_setup_callback = [this]() {
             if (m_child_setup_callback)
                 return m_child_setup_callback();

Userland/DevTools/HackStudio/EditorWrapper.cpp

@@ -113,7 +113,7 @@ void EditorWrapper::set_project_root(DeprecatedString const& project_root)
 void EditorWrapper::update_title()
 {
     StringBuilder title;
-    if (m_filename.is_null())
+    if (m_filename.is_empty())
         title.append(untitled_label);
     else
         title.append(m_filename);

Userland/DevTools/HackStudio/Git/GitRepo.cpp

@@ -24,7 +24,7 @@ GitRepo::CreateResult GitRepo::try_to_create(DeprecatedString const& repository_
 RefPtr<GitRepo> GitRepo::initialize_repository(DeprecatedString const& repository_root)
 {
     auto res = command_wrapper({ "init" }, repository_root);
-    if (res.is_null())
+    if (!res.has_value())
         return {};
 
     VERIFY(git_repo_exists(repository_root));
@@ -42,25 +42,25 @@ Vector<DeprecatedString> GitRepo::unstaged_files() const
 Vector<DeprecatedString> GitRepo::staged_files() const
 {
     auto raw_result = command({ "diff", "--cached", "--name-only" });
-    if (raw_result.is_null())
+    if (!raw_result.has_value())
         return {};
-    return parse_files_list(raw_result);
+    return parse_files_list(*raw_result);
 }
 
 Vector<DeprecatedString> GitRepo::modified_files() const
 {
     auto raw_result = command({ "ls-files", "--modified", "--exclude-standard" });
-    if (raw_result.is_null())
+    if (!raw_result.has_value())
         return {};
-    return parse_files_list(raw_result);
+    return parse_files_list(*raw_result);
 }
 
 Vector<DeprecatedString> GitRepo::untracked_files() const
 {
     auto raw_result = command({ "ls-files", "--others", "--exclude-standard" });
-    if (raw_result.is_null())
+    if (!raw_result.has_value())
         return {};
-    return parse_files_list(raw_result);
+    return parse_files_list(*raw_result);
 }
 
 Vector<DeprecatedString> GitRepo::parse_files_list(DeprecatedString const& raw_result)
@@ -73,12 +73,12 @@ Vector<DeprecatedString> GitRepo::parse_files_list(DeprecatedString const& raw_r
     return files;
 }
 
-DeprecatedString GitRepo::command(Vector<DeprecatedString> const& command_parts) const
+Optional<DeprecatedString> GitRepo::command(Vector<DeprecatedString> const& command_parts) const
 {
     return command_wrapper(command_parts, m_repository_root);
 }
 
-DeprecatedString GitRepo::command_wrapper(Vector<DeprecatedString> const& command_parts, DeprecatedString const& chdir)
+Optional<DeprecatedString> GitRepo::command_wrapper(Vector<DeprecatedString> const& command_parts, DeprecatedString const& chdir)
 {
     auto const result = Core::command("git", command_parts, LexicalPath(chdir));
     if (result.is_error() || result.value().exit_code != 0)
@@ -88,27 +88,27 @@ DeprecatedString GitRepo::command_wrapper(Vector<DeprecatedString> const& comman
 
 bool GitRepo::git_is_installed()
 {
-    return !command_wrapper({ "--help" }, "/").is_null();
+    return command_wrapper({ "--help" }, "/").has_value();
 }
 
 bool GitRepo::git_repo_exists(DeprecatedString const& repo_root)
 {
-    return !command_wrapper({ "status" }, repo_root).is_null();
+    return command_wrapper({ "status" }, repo_root).has_value();
 }
 
 bool GitRepo::stage(DeprecatedString const& file)
 {
-    return !command({ "add", file }).is_null();
+    return command({ "add", file }).has_value();
 }
 
 bool GitRepo::unstage(DeprecatedString const& file)
 {
-    return !command({ "reset", "HEAD", "--", file }).is_null();
+    return command({ "reset", "HEAD", "--", file }).has_value();
 }
 
 bool GitRepo::commit(DeprecatedString const& message)
 {
-    return !command({ "commit", "-m", message }).is_null();
+    return command({ "commit", "-m", message }).has_value();
 }
 
 Optional<DeprecatedString> GitRepo::original_file_content(DeprecatedString const& file) const
@@ -124,10 +124,10 @@ Optional<DeprecatedString> GitRepo::unstaged_diff(DeprecatedString const& file)
 bool GitRepo::is_tracked(DeprecatedString const& file) const
 {
     auto res = command({ "ls-files", file });
-    if (res.is_null())
+    if (!res.has_value())
         return false;
 
-    return !res.is_empty();
+    return !res->is_empty();
 }
 
 }

Userland/DevTools/HackStudio/Git/GitRepo.h

@@ -45,7 +45,7 @@ private:
     static bool git_is_installed();
     static bool git_repo_exists(DeprecatedString const& repo_root);
 
-    static DeprecatedString command_wrapper(Vector<DeprecatedString> const& command_parts, DeprecatedString const& chdir);
+    static Optional<DeprecatedString> command_wrapper(Vector<DeprecatedString> const& command_parts, DeprecatedString const& chdir);
     static Vector<DeprecatedString> parse_files_list(DeprecatedString const&);
 
     explicit GitRepo(DeprecatedString const& repository_root)
@@ -56,7 +56,7 @@ private:
     Vector<DeprecatedString> modified_files() const;
     Vector<DeprecatedString> untracked_files() const;
 
-    DeprecatedString command(Vector<DeprecatedString> const& command_parts) const;
+    Optional<DeprecatedString> command(Vector<DeprecatedString> const& command_parts) const;
 
     DeprecatedString m_repository_root;
 };

Userland/DevTools/HackStudio/HackStudioWidget.cpp

@@ -909,15 +909,15 @@ NonnullRefPtr<GUI::Action> HackStudioWidget::create_save_as_action()
 
         auto suggested_path = FileSystem::absolute_path(old_path.string()).release_value_but_fixme_should_propagate_errors();
         Optional<DeprecatedString> save_path = GUI::FilePicker::get_save_filepath(window(),
-            old_filename.is_null() ? "Untitled"sv : old_path.title(),
-            old_filename.is_null() ? "txt"sv : old_path.extension(),
+            old_filename.is_empty() ? "Untitled"sv : old_path.title(),
+            old_filename.is_empty() ? "txt"sv : old_path.extension(),
             suggested_path);
         if (!save_path.has_value()) {
             return;
         }
 
         DeprecatedString const relative_file_path = LexicalPath::relative_path(save_path.value(), m_project->root_path());
-        if (current_editor_wrapper().filename().is_null()) {
+        if (current_editor_wrapper().filename().is_empty()) {
             current_editor_wrapper().set_filename(relative_file_path);
         } else {
             for (auto& editor_wrapper : m_all_editor_wrappers) {
@@ -1729,7 +1729,7 @@ void HackStudioWidget::update_current_editor_title()
 void HackStudioWidget::on_cursor_change()
 {
     update_statusbar();
-    if (current_editor_wrapper().filename().is_null())
+    if (current_editor_wrapper().filename().is_empty())
         return;
 
     auto current_location = current_project_location();

Userland/DevTools/HackStudio/LanguageServers/FileDB.cpp

@@ -68,9 +68,9 @@ DeprecatedString FileDB::to_absolute_path(DeprecatedString const& filename) cons
     if (LexicalPath { filename }.is_absolute()) {
         return filename;
     }
-    if (m_project_root.is_null())
+    if (!m_project_root.has_value())
         return filename;
-    return LexicalPath { DeprecatedString::formatted("{}/{}", m_project_root, filename) }.string();
+    return LexicalPath { DeprecatedString::formatted("{}/{}", *m_project_root, filename) }.string();
 }
 
 ErrorOr<NonnullRefPtr<GUI::TextDocument>> FileDB::create_from_filesystem(DeprecatedString const& filename) const

Userland/DevTools/HackStudio/LanguageServers/FileDB.h

@@ -38,7 +38,7 @@ private:
 
 private:
     HashMap<DeprecatedString, NonnullRefPtr<GUI::TextDocument>> m_open_files;
-    DeprecatedString m_project_root;
+    Optional<DeprecatedString> m_project_root;
 };
 
 }

Userland/DevTools/HackStudio/Locator.cpp

@@ -60,7 +60,7 @@ public:
         }
         if (suggestion.is_symbol_declaration()) {
             if (index.column() == Column::Name) {
-                if (suggestion.as_symbol_declaration.value().scope.is_null())
+                if (!suggestion.as_symbol_declaration.value().scope.is_empty())
                     return suggestion.as_symbol_declaration.value().name;
                 return DeprecatedString::formatted("{}::{}", suggestion.as_symbol_declaration.value().scope, suggestion.as_symbol_declaration.value().name);
             }