Bug 1411878 - Support Element.shadowRoot and Element.assignedSlot / TextNode.assignedSlot on closed shadow root

Tag #1375

dom/base/Element.cpp

@@ -1104,6 +1104,25 @@ Element::GetSlot(nsAString& aName)
   GetAttr(kNameSpaceID_None, nsGkAtoms::slot, aName);
 }
 
+// https://dom.spec.whatwg.org/#dom-element-shadowroot
+ShadowRoot*
+Element::GetShadowRootByMode() const
+{
+  /**
+   * 1. Let shadow be context object’s shadow root.
+   * 2. If shadow is null or its mode is "closed", then return null.
+   */
+  ShadowRoot* shadowRoot = GetShadowRoot();
+  if (!shadowRoot || shadowRoot->IsClosed()) {
+    return nullptr;
+  }
+
+  /**
+   * 3. Return shadow.
+   */
+  return shadowRoot;
+}
+
 // https://dom.spec.whatwg.org/#dom-element-attachshadow
 already_AddRefed<ShadowRoot>
 Element::AttachShadow(const ShadowRootInit& aInit, ErrorResult& aError)

dom/base/Element.h

@@ -927,6 +927,7 @@ public:
   // Shadow DOM v1
   already_AddRefed<ShadowRoot> AttachShadow(const ShadowRootInit& aInit,
                                             ErrorResult& aError);
+  ShadowRoot* GetShadowRootByMode() const;
   void SetSlot(const nsAString& aName, ErrorResult& aError);
   void GetSlot(nsAString& aName);
 

dom/base/FragmentOrElement.cpp

@@ -152,6 +152,36 @@ nsIContent::FindFirstNonChromeOnlyAccessContent() const
   return nullptr;
 }
 
+// https://dom.spec.whatwg.org/#dom-slotable-assignedslot
+HTMLSlotElement*
+nsIContent::GetAssignedSlotByMode() const
+{
+  /**
+   * Get slotable's assigned slot for the result of
+   * find a slot with open flag UNSET [1].
+   *
+   * [1] https://dom.spec.whatwg.org/#assign-a-slot
+   */
+  HTMLSlotElement* slot = GetAssignedSlot();
+  if (!slot) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(GetParent());
+  MOZ_ASSERT(GetParent()->GetShadowRoot());
+
+  /**
+   * Additional check for open flag SET:
+   *   If slotable’s parent’s shadow root's mode is not "open",
+   *   then return null.
+   */
+  if (GetParent()->GetShadowRoot()->IsClosed()) {
+    return nullptr;
+  }
+
+  return slot;
+}
+
 nsINode*
 nsIContent::GetFlattenedTreeParentNodeInternal(FlattenedParentType aType) const
 {

dom/base/ShadowRoot.h

@@ -51,6 +51,11 @@ public:
   {
     return mMode;
   }
+  bool IsClosed()
+  {
+    return mMode == ShadowRootMode::Closed;
+  }
+
 
   // [deprecated] Shadow DOM v0
   void AddToIdTable(Element* aElement, nsIAtom* aId);

dom/base/nsIContent.h

@@ -724,6 +724,15 @@ public:
    */
   virtual void SetAssignedSlot(mozilla::dom::HTMLSlotElement* aSlot) = 0;
 
+  /**
+   * Gets the assigned slot associated with this content based on parent's
+   * shadow root mode. Returns null if parent's shadow root is "closed".
+   * https://dom.spec.whatwg.org/#dom-slotable-assignedslot
+   *
+   * @return The assigned slot element or null.
+   */
+  mozilla::dom::HTMLSlotElement* GetAssignedSlotByMode() const;
+
   /**
    * Gets the insertion parent element of the XBL binding.
    * The insertion parent is our one true parent in the transformed DOM.

dom/webidl/Element.webidl

@@ -238,9 +238,9 @@ partial interface Element {
   // Shadow DOM v1
   [Throws, Pref="nsDocument::IsWebComponentsEnabled"]
   ShadowRoot attachShadow(ShadowRootInit shadowRootInitDict);
-  [Func="nsDocument::IsWebComponentsEnabled"]
+  [BinaryName="shadowRootByMode", Func="nsDocument::IsWebComponentsEnabled"]
   readonly attribute ShadowRoot? shadowRoot;
-  [Pref="nsDocument::IsWebComponentsEnabled"]
+  [BinaryName="assignedSlotByMode", Pref="nsDocument::IsWebComponentsEnabled"]
   readonly attribute HTMLSlotElement? assignedSlot;
   [CEReactions, Unscopable, SetterThrows, Pref="nsDocument::IsWebComponentsEnabled"]
            attribute DOMString slot;

dom/webidl/Text.webidl

@@ -19,7 +19,7 @@ interface Text : CharacterData {
 };
 
 partial interface Text {
-  [Pref="dom.webcomponents.enabled"]
+  [BinaryName="assignedSlotByMode", Pref="dom.webcomponents.enabled"]
   readonly attribute HTMLSlotElement? assignedSlot;
 };
 

testing/web-platform/meta/shadow-dom/Element-interface-shadowRoot-attribute.html.ini

@@ -1,8 +0,0 @@
-[Element-interface-shadowRoot-attribute.html]
-  type: testharness
-  [shadowRoot attribute must return the open shadow root associated with the element]
-    expected: FAIL
-
-  [shadowRoot attribute must return null if the shadow root attached to the element is closed]
-    expected: FAIL
-