Bug 1906015 - part 1: Add `nsIFormControl` accessors from `nsINode*` or `EventTarget*` r=smaug

Although the following patch do not use the `dom::EventTarget*` versions,
they should be available for consistency with the other `FromNode` related
utility methods.

Differential Revision: https://phabricator.services.mozilla.com/D215576

dom/base/nsINode.h

@@ -45,6 +45,7 @@ class nsIAnimationObserver;
 class nsIContent;
 class nsIContentSecurityPolicy;
 class nsIFrame;
+class nsIFormControl;
 class nsIHTMLCollection;
 class nsMultiMutationObserver;
 class nsINode;
@@ -627,6 +628,16 @@ class nsINode : public mozilla::dom::EventTarget {
   inline mozilla::dom::Text* AsText();
   inline const mozilla::dom::Text* AsText() const;
 
+  /**
+   * Return this node if the instance type inherits nsIFormControl, or an
+   * nsIFormControl instance which ia associated with this node.  Otherwise,
+   * returns nullptr.
+   */
+  [[nodiscard]] virtual nsIFormControl* GetAsFormControl() { return nullptr; }
+  [[nodiscard]] virtual const nsIFormControl* GetAsFormControl() const {
+    return nullptr;
+  }
+
   /*
    * Return whether the node is a ProcessingInstruction node.
    */

dom/html/HTMLElement.cpp

@@ -431,6 +431,14 @@ ElementInternals* HTMLElement::GetElementInternals() const {
   return data->GetElementInternals();
 }
 
+nsIFormControl* HTMLElement::GetAsFormControl() {
+  return GetElementInternals();
+}
+
+const nsIFormControl* HTMLElement::GetAsFormControl() const {
+  return GetElementInternals();
+}
+
 void HTMLElement::UpdateBarredFromConstraintValidation() {
   CustomElementData* data = GetCustomElementData();
   if (data && data->IsFormAssociated()) {

dom/html/HTMLElement.h

@@ -21,6 +21,9 @@ class HTMLElement final : public nsGenericHTMLFormElement {
   NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(HTMLElement,
                                            nsGenericHTMLFormElement)
 
+  [[nodiscard]] nsIFormControl* GetAsFormControl() final;
+  [[nodiscard]] const nsIFormControl* GetAsFormControl() const final;
+
   // EventTarget
   void GetEventTargetParent(EventChainPreVisitor& aVisitor) override;
 

dom/html/nsGenericHTMLElement.cpp

@@ -3777,3 +3777,57 @@ void nsGenericHTMLElement::GetPopover(nsString& aPopover) const {
     aPopover.Assign(NS_ConvertUTF8toUTF16(kPopoverAttributeValueAuto));
   }
 }
+
+/******************************************************************************
+ *  nsIFormControl
+ *****************************************************************************/
+
+// static
+nsIFormControl* nsIFormControl::FromEventTarget(
+    mozilla::dom::EventTarget* aTarget) {
+  MOZ_ASSERT(aTarget);
+  return aTarget->IsNode() ? aTarget->AsNode()->GetAsFormControl() : nullptr;
+}
+
+// static
+nsIFormControl* nsIFormControl::FromEventTargetOrNull(
+    mozilla::dom::EventTarget* aTarget) {
+  return aTarget && aTarget->IsNode() ? aTarget->AsNode()->GetAsFormControl()
+                                      : nullptr;
+}
+
+// static
+const nsIFormControl* nsIFormControl::FromEventTarget(
+    const mozilla::dom::EventTarget* aTarget) {
+  MOZ_ASSERT(aTarget);
+  return aTarget->IsNode() ? aTarget->AsNode()->GetAsFormControl() : nullptr;
+}
+
+// static
+const nsIFormControl* nsIFormControl::FromEventTargetOrNull(
+    const mozilla::dom::EventTarget* aTarget) {
+  return aTarget && aTarget->IsNode() ? aTarget->AsNode()->GetAsFormControl()
+                                      : nullptr;
+}
+
+// static
+nsIFormControl* nsIFormControl::FromNode(nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->GetAsFormControl();
+}
+
+// static
+nsIFormControl* nsIFormControl::FromNodeOrNull(nsINode* aNode) {
+  return aNode ? aNode->GetAsFormControl() : nullptr;
+}
+
+// static
+const nsIFormControl* nsIFormControl::FromNode(const nsINode* aNode) {
+  MOZ_ASSERT(aNode);
+  return aNode->GetAsFormControl();
+}
+
+// static
+const nsIFormControl* nsIFormControl::FromNodeOrNull(const nsINode* aNode) {
+  return aNode ? aNode->GetAsFormControl() : nullptr;
+}

dom/html/nsGenericHTMLElement.h

@@ -1176,6 +1176,11 @@ class nsGenericHTMLFormControlElement : public nsGenericHTMLFormElement,
   NS_IMPL_FROMNODE_HELPER(nsGenericHTMLFormControlElement,
                           IsHTMLFormControlElement())
 
+  [[nodiscard]] nsIFormControl* GetAsFormControl() final { return this; }
+  [[nodiscard]] const nsIFormControl* GetAsFormControl() const final {
+    return this;
+  }
+
   // nsINode
   nsINode* GetScopeChainParent() const override;
   bool IsHTMLFormControlElement() const final { return true; }

dom/html/nsIFormControl.h

@@ -10,10 +10,12 @@
 #include "mozilla/StaticPrefs_dom.h"
 #include "nsISupports.h"
 
+class nsINode;
 namespace mozilla {
 class PresState;
 namespace dom {
 class Element;
+class EventTarget;
 class FormData;
 class HTMLFieldSetElement;
 class HTMLFormElement;
@@ -93,6 +95,19 @@ class nsIFormControl : public nsISupports {
 
   NS_DECLARE_STATIC_IID_ACCESSOR(NS_IFORMCONTROL_IID)
 
+  static nsIFormControl* FromEventTarget(mozilla::dom::EventTarget* aTarget);
+  static nsIFormControl* FromEventTargetOrNull(
+      mozilla::dom::EventTarget* aTarget);
+  static const nsIFormControl* FromEventTarget(
+      const mozilla::dom::EventTarget* aTarget);
+  static const nsIFormControl* FromEventTargetOrNull(
+      const mozilla::dom::EventTarget* aTarget);
+
+  static nsIFormControl* FromNode(nsINode* aNode);
+  static nsIFormControl* FromNodeOrNull(nsINode* aNode);
+  static const nsIFormControl* FromNode(const nsINode* aNode);
+  static const nsIFormControl* FromNodeOrNull(const nsINode* aNode);
+
   /**
    * Get the fieldset for this form control.
    * @return the fieldset