Implement element.shadowRoot attribute (#34306)

* Implement Element.shadowRoot attribute

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Remove comments about shadowdom not being exposed for web content

This is obviously not the case anymore.

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

* Update WPT expectations

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

---------

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

components/script/dom/element.rs

@@ -73,11 +73,13 @@ use crate::dom::attr::{Attr, AttrHelpersForLayout};
 use crate::dom::bindings::cell::{ref_filter_map, DomRefCell, Ref, RefMut};
 use crate::dom::bindings::codegen::Bindings::AttrBinding::AttrMethods;
 use crate::dom::bindings::codegen::Bindings::DocumentBinding::DocumentMethods;
-use crate::dom::bindings::codegen::Bindings::ElementBinding::ElementMethods;
+use crate::dom::bindings::codegen::Bindings::ElementBinding::{ElementMethods, ShadowRootInit};
 use crate::dom::bindings::codegen::Bindings::FunctionBinding::Function;
 use crate::dom::bindings::codegen::Bindings::HTMLTemplateElementBinding::HTMLTemplateElementMethods;
 use crate::dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
-use crate::dom::bindings::codegen::Bindings::ShadowRootBinding::ShadowRoot_Binding::ShadowRootMethods;
+use crate::dom::bindings::codegen::Bindings::ShadowRootBinding::{
+    ShadowRootMethods, ShadowRootMode,
+};
 use crate::dom::bindings::codegen::Bindings::WindowBinding::{
     ScrollBehavior, ScrollToOptions, WindowMethods,
 };
@@ -507,9 +509,11 @@ impl Element {
     }
 
     /// <https://dom.spec.whatwg.org/#dom-element-attachshadow>
-    /// XXX This is not exposed to web content yet. It is meant to be used
-    ///     for UA widgets only.
-    pub fn attach_shadow(&self, is_ua_widget: IsUserAgentWidget) -> Fallible<DomRoot<ShadowRoot>> {
+    pub fn attach_shadow(
+        &self,
+        is_ua_widget: IsUserAgentWidget,
+        mode: ShadowRootMode,
+    ) -> Fallible<DomRoot<ShadowRoot>> {
         // Step 1.
         if self.namespace != ns!(html) {
             return Err(Error::NotSupported);
@@ -546,7 +550,7 @@ impl Element {
         }
 
         // Steps 4, 5 and 6.
-        let shadow_root = ShadowRoot::new(self, &self.node.owner_doc());
+        let shadow_root = ShadowRoot::new(self, &self.node.owner_doc(), mode);
         self.ensure_rare_data().shadow_root = Some(Dom::from_ref(&*shadow_root));
         shadow_root
             .upcast::<Node>()
@@ -3050,11 +3054,29 @@ impl ElementMethods for Element {
         doc.enter_fullscreen(self, can_gc)
     }
 
-    // XXX Hidden under dom.shadowdom.enabled pref. Only exposed to be able
-    //     to test partial Shadow DOM support for UA widgets.
     // https://dom.spec.whatwg.org/#dom-element-attachshadow
-    fn AttachShadow(&self) -> Fallible<DomRoot<ShadowRoot>> {
-        self.attach_shadow(IsUserAgentWidget::No)
+    fn AttachShadow(&self, init: &ShadowRootInit) -> Fallible<DomRoot<ShadowRoot>> {
+        // Step 1. Run attach a shadow root with this, init["mode"], init["clonable"], init["serializable"],
+        // init["delegatesFocus"], and init["slotAssignment"].
+        let shadow_root = self.attach_shadow(IsUserAgentWidget::No, init.mode)?;
+
+        // Step 2. Return this’s shadow root.
+        Ok(shadow_root)
+    }
+
+    /// <https://dom.spec.whatwg.org/#dom-element-shadowroot>
+    fn GetShadowRoot(&self) -> Option<DomRoot<ShadowRoot>> {
+        // Step 1. Let shadow be this’s shadow root.
+        let shadow_or_none = self.shadow_root();
+
+        // Step 2. If shadow is null or its mode is "closed", then return null.
+        let shadow = shadow_or_none?;
+        if shadow.Mode() == ShadowRootMode::Closed {
+            return None;
+        }
+
+        // Step 3. Return shadow.
+        Some(shadow)
     }
 
     fn GetRole(&self) -> Option<DOMString> {

components/script/dom/htmlmediaelement.rs

@@ -54,6 +54,7 @@ use crate::dom::bindings::codegen::Bindings::MediaErrorBinding::MediaErrorConsta
 use crate::dom::bindings::codegen::Bindings::MediaErrorBinding::MediaErrorMethods;
 use crate::dom::bindings::codegen::Bindings::NavigatorBinding::Navigator_Binding::NavigatorMethods;
 use crate::dom::bindings::codegen::Bindings::NodeBinding::Node_Binding::NodeMethods;
+use crate::dom::bindings::codegen::Bindings::ShadowRootBinding::ShadowRootMode;
 use crate::dom::bindings::codegen::Bindings::TextTrackBinding::{TextTrackKind, TextTrackMode};
 use crate::dom::bindings::codegen::Bindings::URLBinding::URLMethods;
 use crate::dom::bindings::codegen::Bindings::WindowBinding::Window_Binding::WindowMethods;
@@ -1908,7 +1909,9 @@ impl HTMLMediaElement {
             // if we are already showing the controls.
             return;
         }
-        let shadow_root = element.attach_shadow(IsUserAgentWidget::Yes).unwrap();
+        let shadow_root = element
+            .attach_shadow(IsUserAgentWidget::Yes, ShadowRootMode::Closed)
+            .unwrap();
         let document = document_from_node(self);
         let script = HTMLScriptElement::new(
             local_name!("script"),

components/script/dom/shadowroot.rs

@@ -36,7 +36,7 @@ pub enum IsUserAgentWidget {
     Yes,
 }
 
-// https://dom.spec.whatwg.org/#interface-shadowroot
+/// <https://dom.spec.whatwg.org/#interface-shadowroot>
 #[dom_struct]
 pub struct ShadowRoot {
     document_fragment: DocumentFragment,
@@ -48,11 +48,14 @@ pub struct ShadowRoot {
     author_styles: DomRefCell<AuthorStyles<StyleSheetInDocument>>,
     stylesheet_list: MutNullableDom<StyleSheetList>,
     window: Dom<Window>,
+
+    /// <https://dom.spec.whatwg.org/#dom-shadowroot-mode>
+    mode: ShadowRootMode,
 }
 
 impl ShadowRoot {
     #[allow(crown::unrooted_must_root)]
-    fn new_inherited(host: &Element, document: &Document) -> ShadowRoot {
+    fn new_inherited(host: &Element, document: &Document, mode: ShadowRootMode) -> ShadowRoot {
         let document_fragment = DocumentFragment::new_inherited(document);
         let node = document_fragment.upcast::<Node>();
         node.set_flag(NodeFlags::IS_IN_SHADOW_TREE, true);
@@ -60,6 +63,7 @@ impl ShadowRoot {
             NodeFlags::IS_CONNECTED,
             host.upcast::<Node>().is_connected(),
         );
+
         ShadowRoot {
             document_fragment,
             document_or_shadow_root: DocumentOrShadowRoot::new(document.window()),
@@ -68,12 +72,13 @@ impl ShadowRoot {
             author_styles: DomRefCell::new(AuthorStyles::new()),
             stylesheet_list: MutNullableDom::new(None),
             window: Dom::from_ref(document.window()),
+            mode,
         }
     }
 
-    pub fn new(host: &Element, document: &Document) -> DomRoot<ShadowRoot> {
+    pub fn new(host: &Element, document: &Document, mode: ShadowRootMode) -> DomRoot<ShadowRoot> {
         reflect_dom_object(
-            Box::new(ShadowRoot::new_inherited(host, document)),
+            Box::new(ShadowRoot::new_inherited(host, document, mode)),
             document.window(),
         )
     }
@@ -226,7 +231,7 @@ impl ShadowRootMethods for ShadowRoot {
 
     /// <https://dom.spec.whatwg.org/#dom-shadowroot-mode>
     fn Mode(&self) -> ShadowRootMode {
-        ShadowRootMode::Closed
+        self.mode
     }
 
     /// <https://dom.spec.whatwg.org/#dom-shadowroot-host>

components/script/dom/webidls/Element.webidl

@@ -83,7 +83,16 @@ interface Element : Node {
   [CEReactions, Throws]
   undefined insertAdjacentHTML(DOMString position, DOMString html);
 
-  [Throws, Pref="dom.shadowdom.enabled"] ShadowRoot attachShadow();
+  [Throws, Pref="dom.shadowdom.enabled"] ShadowRoot attachShadow(ShadowRootInit init);
+  readonly attribute ShadowRoot? shadowRoot;
+};
+
+dictionary ShadowRootInit {
+  required ShadowRootMode mode;
+  // boolean delegatesFocus = false;
+  // SlotAssignmentMode slotAssignment = "named";
+  // boolean clonable = false;
+  // boolean serializable = false;
 };
 
 // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-element-interface

components/script/dom/webidls/ShadowRoot.webidl

@@ -13,5 +13,6 @@ interface ShadowRoot : DocumentFragment {
 };
 
 enum ShadowRootMode { "open", "closed"};
+// enum SlotAssignmentMode { "manual", "named" };
 
 ShadowRoot includes DocumentOrShadowRoot;