LibURL+Everywhere: Only percent decode URL paths when actually needed

Web specs do not return through javascript percent decoded URL path
components - but we were doing this in a number of places due to the
default behaviour of URL::serialize_path.

Since percent encoded URL paths may not contain valid UTF-8 - this was
resulting in us crashing in these places.

For example - on an HTMLAnchorElement when retrieving the pathname for
the URL of:

http://ladybird.org/foo%C2%91%91

To fix this make the URL class only return the percent encoded
serialized path, matching the URL spec. When the decoded path is
required instead explicitly call URL::percent_decode.

This fixes a crash running WPT URL tests for the anchor element on:

https://wpt.live/url/a-element.html
(cherry picked from commit cc557323326ba55514ef2a8a6e0efd7f09330f06;
amended heavily to call `URL::percent_decode()` on all results of
`url.serialize_path()` in the rest of serenity -- except in
LibGemini, where it looked incorrect, and in LibHTTP, where
LadybirdBrowser/ladybird#983 will add it.)

Tests/LibURL/TestURL.cpp

@@ -159,7 +159,8 @@ TEST_CASE(file_url_with_encoded_characters)
     URL::URL url("file:///my/file/test%23file.txt"sv);
     EXPECT(url.is_valid());
     EXPECT_EQ(url.scheme(), "file");
-    EXPECT_EQ(url.serialize_path(), "/my/file/test#file.txt");
+    EXPECT_EQ(url.serialize_path(), "/my/file/test%23file.txt");
+    EXPECT_EQ(URL::percent_decode(url.serialize_path()), "/my/file/test#file.txt");
     EXPECT(!url.query().has_value());
     EXPECT(!url.fragment().has_value());
 }
@@ -332,7 +333,8 @@ TEST_CASE(unicode)
 {
     URL::URL url { "http://example.com/_ünicöde_téxt_©"sv };
     EXPECT(url.is_valid());
-    EXPECT_EQ(url.serialize_path(), "/_ünicöde_téxt_©");
+    EXPECT_EQ(url.serialize_path(), "/_%C3%BCnic%C3%B6de_t%C3%A9xt_%C2%A9");
+    EXPECT_EQ(URL::percent_decode(url.serialize_path()), "/_ünicöde_téxt_©");
     EXPECT(!url.query().has_value());
     EXPECT(!url.fragment().has_value());
 }

Tests/LibWeb/Text/expected/HTML/anchor-element-url-invalid-unicode-pathname.txt

@@ -0,0 +1 @@
+   /foo%C2%91%91

Tests/LibWeb/Text/input/HTML/anchor-element-url-invalid-unicode-pathname.html

@@ -0,0 +1,8 @@
+<a id="anchor" href="http://ladybird.org/foo%C2%91%91"></a>
+<script src="../include.js"></script>
+<script>
+    test(() => {
+        const anchorElement = document.getElementById('anchor');
+        println(anchorElement.pathname);
+    })
+</script>

Userland/Applications/3DFileViewer/main.cpp

@@ -150,7 +150,7 @@ void GLContextWidget::drop_event(GUI::DropEvent& event)
         if (url.scheme() != "file")
             continue;
 
-        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), url.serialize_path());
+        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), URL::percent_decode(url.serialize_path()));
         if (response.is_error())
             return;
         load_file(response.value().filename(), response.value().release_stream());

Userland/Applications/FileManager/FileUtils.cpp

@@ -129,7 +129,7 @@ ErrorOr<bool> handle_drop(GUI::DropEvent const& event, ByteString const& destina
 
     Vector<ByteString> paths_to_copy;
     for (auto& url_to_copy : urls) {
-        auto file_path = url_to_copy.serialize_path();
+        auto file_path = URL::percent_decode(url_to_copy.serialize_path());
         if (!url_to_copy.is_valid() || file_path == target)
             continue;
         auto new_path = ByteString::formatted("{}/{}", target, LexicalPath::basename(file_path));

Userland/Applications/FileManager/main.cpp

@@ -202,7 +202,7 @@ void do_paste(ByteString const& target_directory, GUI::Window* window)
             dbgln("Cannot paste URI {}", uri_as_string);
             continue;
         }
-        source_paths.append(url.serialize_path());
+        source_paths.append(URL::percent_decode(url.serialize_path()));
     }
 
     if (!source_paths.is_empty()) {

Userland/Applications/FontEditor/MainWidget.cpp

@@ -1010,7 +1010,7 @@ void MainWidget::drop_event(GUI::DropEvent& event)
         if (!request_close())
             return;
 
-        auto file_path = urls.first().serialize_path();
+        auto file_path = URL::percent_decode(urls.first().serialize_path());
         auto result = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), file_path);
         if (result.is_error())
             return;

Userland/Applications/Help/MainWidget.cpp

@@ -120,7 +120,7 @@ ErrorOr<void> MainWidget::initialize(GUI::Window& window)
     m_web_view->use_native_user_style_sheet();
     m_web_view->on_link_click = [this](auto& url, auto&, unsigned) {
         if (url.scheme() == "file") {
-            auto path = LexicalPath { url.serialize_path() };
+            auto path = LexicalPath { URL::percent_decode(url.serialize_path()) };
             if (!path.is_child_of(Manual::manual_base_path)) {
                 open_external(url);
                 return;
@@ -253,7 +253,7 @@ void MainWidget::open_url(URL::URL const& url)
     if (url.scheme() == "file") {
         m_web_view->load(url);
 
-        auto browse_view_index = m_manual_model->index_from_path(url.serialize_path());
+        auto browse_view_index = m_manual_model->index_from_path(URL::percent_decode(url.serialize_path()));
         if (browse_view_index.has_value()) {
             if (browse_view_index.value() != m_browse_view->selection_start_index()) {
                 m_browse_view->expand_all_parents_of(browse_view_index.value());

Userland/Applications/HexEditor/HexEditorWidget.cpp

@@ -851,7 +851,7 @@ void HexEditorWidget::drop_event(GUI::DropEvent& event)
             return;
 
         // TODO: A drop event should be considered user consent for opening a file
-        auto response = FileSystemAccessClient::Client::the().request_file(window(), urls.first().serialize_path(), Core::File::OpenMode::Read);
+        auto response = FileSystemAccessClient::Client::the().request_file(window(), URL::percent_decode(urls.first().serialize_path()), Core::File::OpenMode::Read);
         if (response.is_error())
             return;
         open_file(response.value().filename(), response.value().release_stream());

Userland/Applications/ImageViewer/main.cpp

@@ -100,7 +100,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
         window->move_to_front();
 
-        auto path = urls.first().serialize_path();
+        auto path = URL::percent_decode(urls.first().serialize_path());
         auto result = FileSystemAccessClient::Client::the().request_file_read_only_approved(window, path);
         if (result.is_error())
             return;
@@ -109,7 +109,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         widget.open_file(MUST(String::from_byte_string(value.filename())), value.stream());
 
         for (size_t i = 1; i < urls.size(); ++i) {
-            Desktop::Launcher::open(URL::create_with_file_scheme(urls[i].serialize_path().characters()), "/bin/ImageViewer");
+            Desktop::Launcher::open(URL::create_with_file_scheme(URL::percent_decode(urls[i].serialize_path()).characters()), "/bin/ImageViewer");
         }
     };
     widget.on_doubleclick = [&] {

Userland/Applications/PDFViewer/PDFViewerWidget.cpp

@@ -542,7 +542,7 @@ void PDFViewerWidget::drop_event(GUI::DropEvent& event)
             return;
         }
 
-        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), urls.first().serialize_path());
+        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), URL::percent_decode(urls.first().serialize_path()));
         if (response.is_error())
             return;
         if (auto result = try_open_file(response.value().filename(), response.value().release_stream()); result.is_error())

Userland/Applications/PixelPaint/MainWidget.cpp

@@ -1511,7 +1511,7 @@ void MainWidget::drop_event(GUI::DropEvent& event)
         if (url.scheme() != "file")
             continue;
 
-        auto response = FileSystemAccessClient::Client::the().request_file(window(), url.serialize_path(), Core::File::OpenMode::Read);
+        auto response = FileSystemAccessClient::Client::the().request_file(window(), URL::percent_decode(url.serialize_path()), Core::File::OpenMode::Read);
         if (response.is_error())
             return;
         open_image(response.release_value());

Userland/Applications/Presenter/PresenterWidget.cpp

@@ -220,6 +220,6 @@ void PresenterWidget::drop_event(GUI::DropEvent& event)
             return;
 
         window()->move_to_front();
-        set_file(urls.first().serialize_path());
+        set_file(URL::percent_decode(urls.first().serialize_path()));
     }
 }

Userland/Applications/Run/RunWindow.cpp

@@ -143,7 +143,7 @@ bool RunWindow::run_via_launch(ByteString const& run_input)
     auto url = URL::create_with_url_or_path(run_input);
 
     if (url.scheme() == "file") {
-        auto file_path = url.serialize_path();
+        auto file_path = URL::percent_decode(url.serialize_path());
         auto real_path_or_error = FileSystem::real_path(file_path);
         if (real_path_or_error.is_error()) {
             warnln("Failed to launch '{}': {}", file_path, real_path_or_error.error());

Userland/Applications/SoundPlayer/SoundPlayerWidget.cpp

@@ -162,7 +162,7 @@ void SoundPlayerWidget::drop_event(GUI::DropEvent& event)
             return;
         window()->move_to_front();
         // FIXME: Add all paths from drop event to the playlist
-        play_file_path(urls.first().serialize_path());
+        play_file_path(URL::percent_decode(urls.first().serialize_path()));
     }
 }
 

Userland/Applications/Spreadsheet/HelpWindow.cpp

@@ -86,7 +86,7 @@ HelpWindow::HelpWindow(GUI::Window* parent)
     m_webview->on_link_click = [this](auto& url, auto&, auto&&) {
         VERIFY(url.scheme() == "spreadsheet");
         if (url.host().template has<String>() && url.host().template get<String>() == "example"sv) {
-            auto example_path = url.serialize_path();
+            auto example_path = URL::percent_decode(url.serialize_path());
             auto entry = LexicalPath::basename(example_path);
             auto doc_option = m_docs.get_object(entry);
             if (!doc_option.has_value()) {
@@ -125,7 +125,7 @@ HelpWindow::HelpWindow(GUI::Window* parent)
             widget->add_sheet(sheet.release_nonnull());
             window->show();
         } else if (url.host() == "doc"_string) {
-            auto entry = LexicalPath::basename(url.serialize_path());
+            auto entry = LexicalPath::basename(URL::percent_decode(url.serialize_path()));
             m_webview->load(URL::create_with_data("text/html"sv, render(entry)));
         } else {
             dbgln("Invalid spreadsheet action domain '{}'", url.serialized_host().release_value_but_fixme_should_propagate_errors());

Userland/Applications/Spreadsheet/Spreadsheet.cpp

@@ -265,7 +265,7 @@ Optional<Position> Sheet::position_from_url(const URL::URL& url) const
     }
 
     // FIXME: Figure out a way to do this cross-process.
-    VERIFY(url.serialize_path() == ByteString::formatted("/{}", getpid()));
+    VERIFY(URL::percent_decode(url.serialize_path()) == ByteString::formatted("/{}", getpid()));
 
     return parse_cell_name(url.fragment().value_or(String {}));
 }

Userland/Applications/TextEditor/MainWidget.cpp

@@ -856,7 +856,7 @@ void MainWidget::drop_event(GUI::DropEvent& event)
         if (!request_close())
             return;
 
-        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), urls.first().serialize_path());
+        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), URL::percent_decode(urls.first().serialize_path()));
         if (response.is_error())
             return;
         if (auto result = read_file(response.value().filename(), response.value().stream()); result.is_error())

Userland/Applications/ThemeEditor/MainWidget.cpp

@@ -703,7 +703,7 @@ void MainWidget::drop_event(GUI::DropEvent& event)
         if (request_close() == GUI::Window::CloseRequestDecision::StayOpen)
             return;
 
-        auto response = FileSystemAccessClient::Client::the().request_file(window(), urls.first().serialize_path(), Core::File::OpenMode::Read);
+        auto response = FileSystemAccessClient::Client::the().request_file(window(), URL::percent_decode(urls.first().serialize_path()), Core::File::OpenMode::Read);
         if (response.is_error())
             return;
 

Userland/Applications/VideoPlayer/VideoPlayerWidget.cpp

@@ -284,7 +284,7 @@ void VideoPlayerWidget::drop_event(GUI::DropEvent& event)
             GUI::MessageBox::show_error(window(), "VideoPlayer can only view one clip at a time!"sv);
             return;
         }
-        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), urls.first().serialize_path());
+        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), URL::percent_decode(urls.first().serialize_path()));
         if (response.is_error())
             return;
 

Userland/DevTools/GMLPlayground/MainWidget.cpp

@@ -341,7 +341,7 @@ void MainWidget::drop_event(GUI::DropEvent& event)
         if (request_close() == GUI::Window::CloseRequestDecision::StayOpen)
             return;
 
-        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), urls.first().serialize_path());
+        auto response = FileSystemAccessClient::Client::the().request_file_read_only_approved(window(), URL::percent_decode(urls.first().serialize_path()));
         if (response.is_error())
             return;
         load_file(response.release_value());

Userland/DevTools/HackStudio/Editor.cpp

@@ -365,7 +365,7 @@ void Editor::drop_event(GUI::DropEvent& event)
             return;
         }
         set_current_editor_wrapper(static_cast<EditorWrapper*>(parent()));
-        open_file(urls.first().serialize_path());
+        open_file(URL::percent_decode(urls.first().serialize_path()));
     }
 }
 

Userland/DevTools/SQLStudio/MainWidget.cpp

@@ -483,7 +483,7 @@ void MainWidget::drop_event(GUI::DropEvent& drop_event)
             if (!scheme.bytes_as_string_view().equals_ignoring_ascii_case("file"sv))
                 continue;
 
-            auto lexical_path = LexicalPath(url.serialize_path());
+            auto lexical_path = LexicalPath(URL::percent_decode(url.serialize_path()));
             open_script_from_file(lexical_path);
         }
     }

Userland/Libraries/LibURL/URL.cpp

@@ -236,12 +236,12 @@ bool is_special_scheme(StringView scheme)
 }
 
 // https://url.spec.whatwg.org/#url-path-serializer
-ByteString URL::serialize_path(ApplyPercentDecoding apply_percent_decoding) const
+String URL::serialize_path() const
 {
     // 1. If url has an opaque path, then return url’s path.
     // FIXME: Reimplement this step once we modernize the URL implementation to meet the spec.
     if (cannot_be_a_base_url())
-        return m_data->paths[0].to_byte_string();
+        return m_data->paths[0];
 
     // 2. Let output be the empty string.
     StringBuilder output;
@@ -249,11 +249,11 @@ ByteString URL::serialize_path(ApplyPercentDecoding apply_percent_decoding) cons
     // 3. For each segment of url’s path: append U+002F (/) followed by segment to output.
     for (auto const& segment : m_data->paths) {
         output.append('/');
-        output.append(apply_percent_decoding == ApplyPercentDecoding::Yes ? percent_decode(segment) : segment.to_byte_string());
+        output.append(segment);
     }
 
     // 4. Return output.
-    return output.to_byte_string();
+    return output.to_string_without_validation();
 }
 
 // https://url.spec.whatwg.org/#concept-url-serializer

Userland/Libraries/LibURL/URL.h

@@ -54,11 +54,6 @@ using IPv6Address = Array<u16, 8>;
 // but it is sometimes used as opaque identifier in URLs where a network address is not necessary.
 using Host = Variant<IPv4Address, IPv6Address, String, Empty>;
 
-enum class ApplyPercentDecoding {
-    Yes,
-    No
-};
-
 // https://w3c.github.io/FileAPI/#blob-url-entry
 // NOTE: This represents the raw bytes behind a 'Blob' (and does not yet support a MediaSourceQuery).
 struct BlobURLEntry {
@@ -134,7 +129,7 @@ public:
         m_data->paths.append(String {});
     }
 
-    ByteString serialize_path(ApplyPercentDecoding = ApplyPercentDecoding::Yes) const;
+    String serialize_path() const;
     ByteString serialize(ExcludeFragment = ExcludeFragment::No) const;
     ByteString serialize_for_display() const;
     ByteString to_byte_string() const { return serialize(); }

Userland/Libraries/LibVT/TerminalWidget.cpp

@@ -889,7 +889,7 @@ void TerminalWidget::mousemove_event(GUI::MouseEvent& event)
             auto handlers = Desktop::Launcher::get_handlers_for_url(attribute.href);
             if (!handlers.is_empty()) {
                 auto url = URL::URL(attribute.href);
-                auto path = url.serialize_path();
+                auto path = URL::percent_decode(url.serialize_path());
 
                 auto app_file = Desktop::AppFile::get_for_app(LexicalPath::basename(handlers[0]));
                 auto app_name = app_file->is_valid() ? app_file->name() : LexicalPath::basename(handlers[0]);
@@ -1184,7 +1184,7 @@ void TerminalWidget::context_menu_event(GUI::ContextMenuEvent& event)
         }));
         m_context_menu_for_hyperlink->add_action(GUI::Action::create("Copy &Name", [&](auto&) {
             // file://courage/home/anon/something -> /home/anon/something
-            auto path = URL::URL(m_context_menu_href).serialize_path();
+            auto path = URL::percent_decode(URL::URL(m_context_menu_href).serialize_path());
             // /home/anon/something -> something
             auto name = LexicalPath::basename(path);
             GUI::Clipboard::the().set_plain_text(name);
@@ -1215,7 +1215,7 @@ void TerminalWidget::drop_event(GUI::DropEvent& event)
                 send_non_user_input(" "sv.bytes());
 
             if (url.scheme() == "file") {
-                auto path = url.serialize_path();
+                auto path = URL::percent_decode(url.serialize_path());
                 send_non_user_input(path.bytes());
             } else {
                 auto url_string = url.to_byte_string();

Userland/Libraries/LibWeb/DOMURL/DOMURL.cpp

@@ -363,12 +363,10 @@ void DOMURL::set_port(String const& port)
 }
 
 // https://url.spec.whatwg.org/#dom-url-pathname
-WebIDL::ExceptionOr<String> DOMURL::pathname() const
+String DOMURL::pathname() const
 {
-    auto& vm = realm().vm();
-
     // The pathname getter steps are to return the result of URL path serializing this’s URL.
-    return TRY_OR_THROW_OOM(vm, String::from_byte_string(m_url.serialize_path(URL::ApplyPercentDecoding::No)));
+    return m_url.serialize_path();
 }
 
 // https://url.spec.whatwg.org/#ref-for-dom-url-pathname%E2%91%A0

Userland/Libraries/LibWeb/DOMURL/DOMURL.h

@@ -55,7 +55,7 @@ public:
     WebIDL::ExceptionOr<String> port() const;
     void set_port(String const&);
 
-    WebIDL::ExceptionOr<String> pathname() const;
+    String pathname() const;
     void set_pathname(String const&);
 
     Optional<String> const& fragment() const { return m_url.fragment(); }

Userland/Libraries/LibWeb/HTML/HTMLHyperlinkElementUtils.cpp

@@ -284,10 +284,8 @@ String HTMLHyperlinkElementUtils::pathname() const
     if (!m_url.has_value())
         return String {};
 
-    // 4. If url's cannot-be-a-base-URL is true, then return url's path[0].
-    // 5. If url's path is empty, then return the empty string.
-    // 6. Return "/", followed by the strings in url's path (including empty strings), separated from each other by "/".
-    return MUST(String::from_byte_string(m_url->serialize_path()));
+    // 4. Return the result of URL path serializing url.
+    return m_url->serialize_path();
 }
 
 // https://html.spec.whatwg.org/multipage/links.html#dom-hyperlink-pathname

Userland/Libraries/LibWeb/HTML/Location.cpp

@@ -277,15 +277,13 @@ WebIDL::ExceptionOr<void> Location::set_port(String const&)
 // https://html.spec.whatwg.org/multipage/history.html#dom-location-pathname
 WebIDL::ExceptionOr<String> Location::pathname() const
 {
-    auto& vm = this->vm();
-
     // 1. If this's relevant Document is non-null and its origin is not same origin-domain with the entry settings object's origin, then throw a "SecurityError" DOMException.
     auto const relevant_document = this->relevant_document();
     if (relevant_document && !relevant_document->origin().is_same_origin_domain(entry_settings_object().origin()))
         return WebIDL::SecurityError::create(realm(), "Location's relevant document is not same origin-domain with the entry settings object's origin"_fly_string);
 
     // 2. Return the result of URL path serializing this Location object's url.
-    return TRY_OR_THROW_OOM(vm, String::from_byte_string(url().serialize_path()));
+    return url().serialize_path();
 }
 
 WebIDL::ExceptionOr<void> Location::set_pathname(String const&)

Userland/Libraries/LibWeb/HTML/WorkerLocation.cpp

@@ -92,11 +92,10 @@ WebIDL::ExceptionOr<String> WorkerLocation::port() const
 }
 
 // https://html.spec.whatwg.org/multipage/workers.html#dom-workerlocation-pathname
-WebIDL::ExceptionOr<String> WorkerLocation::pathname() const
+String WorkerLocation::pathname() const
 {
-    auto& vm = realm().vm();
     // The pathname getter steps are to return the result of URL path serializing this's WorkerGlobalScope object's url.
-    return TRY_OR_THROW_OOM(vm, String::from_byte_string(m_global_scope->url().serialize_path()));
+    return m_global_scope->url().serialize_path();
 }
 
 // https://html.spec.whatwg.org/multipage/workers.html#dom-workerlocation-search

Userland/Libraries/LibWeb/HTML/WorkerLocation.h

@@ -24,7 +24,7 @@ public:
     WebIDL::ExceptionOr<String> host() const;
     WebIDL::ExceptionOr<String> hostname() const;
     WebIDL::ExceptionOr<String> port() const;
-    WebIDL::ExceptionOr<String> pathname() const;
+    String pathname() const;
     WebIDL::ExceptionOr<String> search() const;
     WebIDL::ExceptionOr<String> hash() const;
 

Userland/Libraries/LibWeb/Loader/GeneratedPagesLoader.cpp

@@ -42,7 +42,7 @@ ErrorOr<String> load_error_page(URL::URL const& url, StringView error_message)
 ErrorOr<String> load_file_directory_page(URL::URL const& url)
 {
     // Generate HTML contents entries table
-    auto lexical_path = LexicalPath(url.serialize_path());
+    auto lexical_path = LexicalPath(URL::percent_decode(url.serialize_path()));
     Core::DirIterator dt(lexical_path.string(), Core::DirIterator::Flags::SkipParentAndBaseDir);
     Vector<ByteString> names;
     while (dt.has_next())

Userland/Libraries/LibWeb/Loader/Resource.cpp

@@ -100,14 +100,14 @@ void Resource::did_load(Badge<ResourceLoader>, ReadonlyBytes data, HTTP::HeaderM
         // FIXME: "The Quite OK Image Format" doesn't have an official mime type yet,
         //        and servers like nginx will send a generic octet-stream mime type instead.
         //        Let's use image/x-qoi for now, which is also what our Core::MimeData uses & would guess.
-        if (m_mime_type == "application/octet-stream" && url().serialize_path().ends_with(".qoi"sv))
+        if (m_mime_type == "application/octet-stream" && URL::percent_decode(url().serialize_path()).ends_with(".qoi"sv))
             m_mime_type = "image/x-qoi";
     } else {
         auto content_type_options = headers.get("X-Content-Type-Options");
         if (content_type_options.value_or("").equals_ignoring_ascii_case("nosniff"sv)) {
             m_mime_type = "text/plain";
         } else {
-            m_mime_type = Core::guess_mime_type_based_on_filename(url().serialize_path());
+            m_mime_type = Core::guess_mime_type_based_on_filename(URL::percent_decode(url().serialize_path()));
         }
     }
 

Userland/Libraries/LibWeb/Loader/ResourceLoader.cpp

@@ -329,7 +329,7 @@ void ResourceLoader::load(LoadRequest& request, SuccessCallback success_callback
         }
 
         auto data = resource.value()->data();
-        auto response_headers = response_headers_for_file(url.serialize_path(), resource.value()->modified_time());
+        auto response_headers = response_headers_for_file(URL::percent_decode(url.serialize_path()), resource.value()->modified_time());
 
         log_success(request);
         success_callback(data, response_headers, {});
@@ -346,7 +346,7 @@ void ResourceLoader::load(LoadRequest& request, SuccessCallback success_callback
             return;
         }
 
-        FileRequest file_request(url.serialize_path(), [this, success_callback = move(success_callback), error_callback = move(error_callback), request, respond_directory_page](ErrorOr<i32> file_or_error) {
+        FileRequest file_request(URL::percent_decode(url.serialize_path()), [this, success_callback = move(success_callback), error_callback = move(error_callback), request, respond_directory_page](ErrorOr<i32> file_or_error) {
             --m_pending_loads;
             if (on_load_counter_change)
                 on_load_counter_change();
@@ -394,7 +394,7 @@ void ResourceLoader::load(LoadRequest& request, SuccessCallback success_callback
             }
 
             auto data = maybe_data.release_value();
-            auto response_headers = response_headers_for_file(request.url().serialize_path(), st_or_error.value().st_mtime);
+            auto response_headers = response_headers_for_file(URL::percent_decode(request.url().serialize_path()), st_or_error.value().st_mtime);
 
             log_success(request);
             success_callback(data, response_headers, {});

Userland/Libraries/LibWebSocket/ConnectionInfo.cpp

@@ -26,7 +26,7 @@ ByteString ConnectionInfo::resource_name() const
     // The "resource-name" can be constructed by concatenating the following:
     StringBuilder builder;
     // "/" if the path component is empty
-    auto path = m_url.serialize_path();
+    auto path = URL::percent_decode(m_url.serialize_path());
     if (path.is_empty())
         builder.append('/');
     // The path component

Userland/Libraries/LibWebView/CookieJar.cpp

@@ -287,7 +287,7 @@ String CookieJar::default_path(const URL::URL& url)
     // https://tools.ietf.org/html/rfc6265#section-5.1.4
 
     // 1. Let uri-path be the path portion of the request-uri if such a portion exists (and empty otherwise).
-    auto uri_path = url.serialize_path();
+    auto uri_path = URL::percent_decode(url.serialize_path());
 
     // 2. If the uri-path is empty or if the first character of the uri-path is not a %x2F ("/") character, output %x2F ("/") and skip the remaining steps.
     if (uri_path.is_empty() || (uri_path[0] != '/'))
@@ -301,6 +301,7 @@ String CookieJar::default_path(const URL::URL& url)
         return "/"_string;
 
     // 4. Output the characters of the uri-path from the first character up to, but not including, the right-most %x2F ("/").
+    // FIXME: The path might not be valid UTF-8.
     return MUST(String::from_utf8(uri_path.substring_view(0, last_separator)));
 }
 

Userland/Services/LaunchServer/Launcher.cpp

@@ -149,7 +149,7 @@ Vector<ByteString> Launcher::handlers_for_url(const URL::URL& url)
 {
     Vector<ByteString> handlers;
     if (url.scheme() == "file") {
-        for_each_handler_for_path(url.serialize_path(), [&](auto& handler) -> bool {
+        for_each_handler_for_path(URL::percent_decode(url.serialize_path()), [&](auto& handler) -> bool {
             handlers.append(handler.executable);
             return true;
         });
@@ -169,7 +169,7 @@ Vector<ByteString> Launcher::handlers_with_details_for_url(const URL::URL& url)
 {
     Vector<ByteString> handlers;
     if (url.scheme() == "file") {
-        for_each_handler_for_path(url.serialize_path(), [&](auto& handler) -> bool {
+        for_each_handler_for_path(URL::percent_decode(url.serialize_path()), [&](auto& handler) -> bool {
             handlers.append(handler.to_details_str());
             return true;
         });
@@ -214,7 +214,7 @@ bool Launcher::open_with_handler_name(const URL::URL& url, ByteString const& han
     auto& handler = handler_optional.value();
     ByteString argument;
     if (url.scheme() == "file")
-        argument = url.serialize_path();
+        argument = URL::percent_decode(url.serialize_path());
     else
         argument = url.to_byte_string();
     return spawn(handler.executable, { argument });
@@ -357,7 +357,7 @@ void Launcher::for_each_handler_for_path(ByteString const& path, Function<bool(H
 bool Launcher::open_file_url(const URL::URL& url)
 {
     struct stat st;
-    auto file_path = url.serialize_path();
+    auto file_path = URL::percent_decode(url.serialize_path());
     if (stat(file_path.characters(), &st) < 0) {
         perror("stat");
         return false;
@@ -399,7 +399,7 @@ bool Launcher::open_file_url(const URL::URL& url)
 
     // Additional parameters parsing, specific for the file protocol and txt file handlers
     Vector<ByteString> additional_parameters;
-    ByteString filepath = url.serialize_path();
+    ByteString filepath = URL::percent_decode(url.serialize_path());
 
     if (url.query().has_value()) {
         url.query()->bytes_as_string_view().for_each_split_view('&', SplitBehavior::Nothing, [&](auto parameter) {

Userland/Services/Taskbar/QuickLaunchWidget.cpp

@@ -164,7 +164,7 @@ void QuickLaunchWidget::drop_event(GUI::DropEvent& event)
     if (event.mime_data().has_urls()) {
         auto urls = event.mime_data().urls();
         for (auto& url : urls) {
-            auto path = url.serialize_path();
+            auto path = URL::percent_decode(url.serialize_path());
             auto entry = QuickLaunchEntry::create_from_path(path);
             if (entry) {
                 auto entry_name = entry->name();

Userland/Utilities/markdown-check.cpp

@@ -204,13 +204,13 @@ RecursionDecision MarkdownLinkage::visit(Markdown::Text::LinkNode const& link_no
             }
 
             // Remove leading '/' from the path.
-            auto file = ByteString::formatted("{}/Base/usr/share/man/man{}.md", m_serenity_source_directory, url.serialize_path().substring(1));
+            auto file = ByteString::formatted("{}/Base/usr/share/man/man{}.md", m_serenity_source_directory, URL::percent_decode(url.serialize_path()).substring(1));
 
             m_file_links.append({ file, ByteString(), StringCollector::from(*link_node.text) });
             return RecursionDecision::Recurse;
         }
         if (url.scheme() == "file") {
-            auto file_path = url.serialize_path();
+            auto file_path = URL::percent_decode(url.serialize_path());
             if (file_path.contains("man"sv) && file_path.ends_with(".md"sv)) {
                 warnln("Inter-manpage link without the help:// scheme: {}\nPlease use help URLs of the form 'help://man/<section>/<subsection...>/<page>'", href);
                 m_has_invalid_link = true;

Userland/Utilities/pro.cpp

@@ -331,7 +331,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
                 }
 
                 if (output_name.is_empty())
-                    output_name = url.serialize_path();
+                    output_name = URL::percent_decode(url.serialize_path());
 
                 LexicalPath path { output_name };
                 output_name = path.basename();

Userland/Utilities/xml.cpp

@@ -371,7 +371,7 @@ static auto parse(StringView contents)
                 if (url.scheme() != "file")
                     return Error::from_string_literal("NYI: Nonlocal entity");
 
-                auto file = TRY(Core::File::open(url.serialize_path(), Core::File::OpenMode::Read));
+                auto file = TRY(Core::File::open(URL::percent_decode(url.serialize_path()), Core::File::OpenMode::Read));
                 return ByteString::copy(TRY(file->read_until_eof()));
             },
         },
@@ -440,7 +440,7 @@ static void do_run_tests(XML::Document& document)
                 continue;
             }
 
-            auto file_path = url.serialize_path();
+            auto file_path = URL::percent_decode(url.serialize_path());
             auto file_result = Core::File::open(file_path, Core::File::OpenMode::Read);
             if (file_result.is_error()) {
                 warnln("Read error for {}: {}", file_path, file_result.error());