Applications: Improve FSAC error message handling

Fixes apps showing redundant error messages and terminating
unnecessarily on failed file requests. It's nicer to drop the
user off at the equivalent of a default document on failure if
possible.

Also fixes TextEditor not showing response errors for missing files
in the recently opened list.

Userland/Applications/FontEditor/main.cpp

@@ -59,14 +59,13 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     auto default_path = TRY(String::from_deprecated_string(Config::read_string("FontEditor"sv, "Defaults"sv, "Font"sv, {})));
     auto path_to_load = path.is_empty() ? default_path : path;
-    auto open_or_error = [&]() -> ErrorOr<void> {
+    if (!path_to_load.is_empty()) {
-        if (path_to_load.is_empty())
+        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window, path_to_load);
-            return {};
+        if (!response.is_error()) {
-        auto file = TRY(FileSystemAccessClient::Client::the().request_file_read_only_approved(window, path_to_load));
+            if (auto result = font_editor->open_file(path, response.value().release_stream()); result.is_error())
-        return TRY(font_editor->open_file(path, file.release_stream()));
+                font_editor->show_error(result.release_error(), "Opening"sv, path_to_load);
-    }();
+        }
-    if (open_or_error.is_error())
+    }
-        font_editor->show_error(open_or_error.release_error(), "Opening"sv, path_to_load);
 
     return app->exec();
 }

Userland/Applications/HexEditor/main.cpp

@@ -55,8 +55,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     if (arguments.argc > 1) {
         // FIXME: Using `try_request_file_read_only_approved` doesn't work here since the file stored in the editor is only readable.
         auto response = FileSystemAccessClient::Client::the().request_file(window, arguments.strings[1], Core::File::OpenMode::ReadWrite);
-        if (response.is_error())
+        if (!response.is_error())
-            return 1;
             hex_editor_widget->open_file(response.value().filename(), response.value().release_stream());
     }
 

Userland/Applications/PixelPaint/main.cpp

@@ -75,9 +75,10 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     if (!image_file.is_empty()) {
         auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window, image_file);
-        if (response.is_error())
+        if (!response.is_error())
-            return 1;
             main_widget->open_image(response.release_value());
+        else
+            TRY(main_widget->create_default_image());
     } else {
         TRY(main_widget->create_default_image());
     }

Userland/Applications/TextEditor/main.cpp

@@ -76,19 +76,20 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     if (!file_to_edit.is_empty()) {
         auto filename = TRY(String::from_utf8(file_to_edit));
         FileArgument parsed_argument(filename);
+
+        FileSystemAccessClient::Client::the().set_silence_errors(FileSystemAccessClient::ErrorFlag::NoEntries);
         auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window, parsed_argument.filename().to_deprecated_string());
 
         if (response.is_error()) {
             if (response.error().code() == ENOENT)
                 text_widget->open_nonexistent_file(parsed_argument.filename().to_deprecated_string());
-            else
-                return 1;
         } else {
             TRY(text_widget->read_file(response.value().filename(), response.value().stream()));
             text_widget->editor().set_cursor_and_focus_line(parsed_argument.line().value_or(1) - 1, parsed_argument.column().value_or(0));
         }
 
         text_widget->update_title();
+        FileSystemAccessClient::Client::the().set_silence_errors(FileSystemAccessClient::ErrorFlag::None);
     }
     text_widget->update_statusbar();
 

Userland/Applications/ThemeEditor/main.cpp

@@ -53,9 +53,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         app->event_loop().deferred_invoke(
             [&window, &path, &main_widget]() {
                 auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window, path.value().to_deprecated_string());
-                if (response.is_error())
+                if (!response.is_error()) {
-                    GUI::MessageBox::show_error(window, DeprecatedString::formatted("Opening \"{}\" failed: {}", path.value(), response.error()));
-                else {
                     auto load_from_file_result = main_widget->load_from_file(response.value().filename(), response.value().release_stream());
                     if (load_from_file_result.is_error())
                         GUI::MessageBox::show_error(window, DeprecatedString::formatted("Loading theme from file has failed: {}", load_from_file_result.error()));