From 32f1ff0f8d3bf009f4e7b57dc75e86b5220f86ed Mon Sep 17 00:00:00 2001
From: Gaming4JC <g4jc@hyperbola.info>
Date: Sun, 5 Jan 2020 10:26:29 -0500
Subject: Bug 1299363 - Part 1: Implement construction stack.

Tag UXP Issue #1344
---
 dom/base/CustomElementRegistry.h |  6 ++++--
 dom/bindings/BindingUtils.cpp    | 37 ++++++++++++++++++++++++++-----------
 2 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/dom/base/CustomElementRegistry.h b/dom/base/CustomElementRegistry.h
index 33f2a95ff..84a7fe3ac 100644
--- a/dom/base/CustomElementRegistry.h
+++ b/dom/base/CustomElementRegistry.h
@@ -106,6 +106,8 @@ private:
   virtual ~CustomElementData() {}
 };
 
+#define ALEADY_CONSTRUCTED_MARKER nullptr
+
 // The required information for a custom element as defined in:
 // https://html.spec.whatwg.org/multipage/scripting.html#custom-element-definition
 struct CustomElementDefinition
@@ -132,8 +134,8 @@ struct CustomElementDefinition
   // The lifecycle callbacks to call for this custom element.
   UniquePtr<mozilla::dom::LifecycleCallbacks> mCallbacks;
 
-  // A construction stack.
-  // TODO: Bug 1287348 - Implement construction stack for upgrading an element
+  // A construction stack. Use nullptr to represent an "already constructed marker".
+  nsTArray<RefPtr<nsGenericHTMLElement>> mConstructionStack;
 
   // The document custom element order.
   uint32_t mDocOrder;
diff --git a/dom/bindings/BindingUtils.cpp b/dom/bindings/BindingUtils.cpp
index 6c35da05e..4d20a95f7 100644
--- a/dom/bindings/BindingUtils.cpp
+++ b/dom/bindings/BindingUtils.cpp
@@ -3539,20 +3539,35 @@ CreateHTMLElement(const GlobalObject& aGlobal, const JS::CallArgs& aCallArgs,
 
   // Step 6 and Step 7 are in the code output by CGClassConstructor.
   // Step 8.
-  // Construction stack will be implemented in bug 1287348. So we always run
-  // "construction stack is empty" case for now.
-  RefPtr<nsGenericHTMLElement> element;
-  if (tag == eHTMLTag_userdefined) {
-    // Autonomous custom element.
-    element = NS_NewHTMLElement(nodeInfo.forget());
-  } else {
-    // Customized built-in element.
-    element = CreateHTMLElement(tag, nodeInfo.forget(), NOT_FROM_PARSER);
+  nsTArray<RefPtr<nsGenericHTMLElement>>& constructionStack =
+    definition->mConstructionStack;
+  if (constructionStack.IsEmpty()) {
+    RefPtr<nsGenericHTMLElement> newElement;
+    if (tag == eHTMLTag_userdefined) {
+      // Autonomous custom element.
+      newElement = NS_NewHTMLElement(nodeInfo.forget());
+    } else {
+      // Customized built-in element.
+      newElement = CreateHTMLElement(tag, nodeInfo.forget(), NOT_FROM_PARSER);
+    }
+
+    newElement->SetCustomElementData(
+      new CustomElementData(definition->mType, CustomElementData::State::eCustom));
+
+    return newElement.forget();
   }
 
-  element->SetCustomElementData(
-    new CustomElementData(definition->mType, CustomElementData::State::eCustom));
+  // Step 9.
+  RefPtr<nsGenericHTMLElement>& element = constructionStack.LastElement();
+
+  // Step 10.
+  if (element == ALEADY_CONSTRUCTED_MARKER) {
+    aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
+    return nullptr;
+  }
 
+  // Step 11 is in the code output by CGClassConstructor.
+  // Step 12 and Step 13.
   return element.forget();
 }
 
-- 
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