Form-associated custom elements: Add more state checks

 - HTMLElement.prototype.attachInternals() should throw InvalidStateErrors
   for customized built-in elements.
 - Form-related operations and attributes of ElementInternals should throw
   InvalidStateErrors for non-form-associated custom elements.

Bug: 905922
Bug: https://github.com/w3c/webcomponents/issues/187
Change-Id: I09e574a843296b236fe4c63eb2cd0912c7a673b1
Reviewed-on: https://chromium-review.googlesource.com/c/1353035Reviewed-by: Hayato Ito <hayato@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611960}

third_party/blink/renderer/core/html/custom/element_internals.cc

@@ -25,12 +25,20 @@ void ElementInternals::Trace(Visitor* visitor) {
   ScriptWrappable::Trace(visitor);
 }
 
-void ElementInternals::setFormValue(const FileOrUSVString& value) {
-  setFormValue(value, nullptr);
+void ElementInternals::setFormValue(const FileOrUSVString& value,
+                                    ExceptionState& exception_state) {
+  setFormValue(value, nullptr, exception_state);
 }
 
 void ElementInternals::setFormValue(const FileOrUSVString& value,
-                                    FormData* entry_source) {
+                                    FormData* entry_source,
+                                    ExceptionState& exception_state) {
+  if (!Target().IsFormAssociatedCustomElement()) {
+    exception_state.ThrowDOMException(
+        DOMExceptionCode::kInvalidStateError,
+        "The target element is not a form-associated custom element.");
+    return;
+  }
   if (!entry_source || entry_source->size() == 0u) {
     value_ = value;
     entry_source_ = nullptr;
@@ -40,7 +48,13 @@ void ElementInternals::setFormValue(const FileOrUSVString& value,
   entry_source_ = MakeGarbageCollected<FormData>(*entry_source);
 }
 
-HTMLFormElement* ElementInternals::form() const {
+HTMLFormElement* ElementInternals::form(ExceptionState& exception_state) const {
+  if (!Target().IsFormAssociatedCustomElement()) {
+    exception_state.ThrowDOMException(
+        DOMExceptionCode::kInvalidStateError,
+        "The target element is not a form-associated custom element.");
+    return nullptr;
+  }
   return ListedElement::Form();
 }
 
@@ -49,7 +63,7 @@ void ElementInternals::DidUpgrade() {
   if (!parent)
     return;
   InsertedInto(*parent);
-  if (auto* owner_form = form()) {
+  if (auto* owner_form = Form()) {
     if (auto* lists = owner_form->NodeLists())
       lists->InvalidateCaches(nullptr);
   }
@@ -97,7 +111,7 @@ void ElementInternals::AppendToFormData(FormData& form_data) {
 
 void ElementInternals::DidChangeForm() {
   ListedElement::DidChangeForm();
-  CustomElement::EnqueueFormAssociatedCallback(Target(), form());
+  CustomElement::EnqueueFormAssociatedCallback(Target(), Form());
 }
 
 }  // namespace blink

third_party/blink/renderer/core/html/custom/element_internals.h

@@ -26,9 +26,12 @@ class ElementInternals : public ScriptWrappable, public ListedElement {
   void DidUpgrade();
 
   // IDL attributes/operations
-  void setFormValue(const FileOrUSVString& value);
-  void setFormValue(const FileOrUSVString& value, FormData* entry_source);
-  HTMLFormElement* form() const;
+  void setFormValue(const FileOrUSVString& value,
+                    ExceptionState& exception_state);
+  void setFormValue(const FileOrUSVString& value,
+                    FormData* entry_source,
+                    ExceptionState& exception_state);
+  HTMLFormElement* form(ExceptionState& exception_state) const;
 
  private:
   // ListedElement overrides:

third_party/blink/renderer/core/html/custom/element_internals.idl

@@ -10,7 +10,7 @@
 ]
 interface ElementInternals {
   // Attributes and operations for form-associated custom elements.
-  void setFormValue(FormDataEntryValue value, optional FormData entrySource);
-  readonly attribute HTMLFormElement? form;
+  [RaisesException] void setFormValue(FormDataEntryValue value, optional FormData entrySource);
+  [RaisesException] readonly attribute HTMLFormElement? form;
 };
 

third_party/blink/renderer/core/html/html_element.cc

@@ -1436,6 +1436,12 @@ ElementInternals* HTMLElement::attachInternals(
         "Unable to attach ElementInternals to non-custom elements.");
     return nullptr;
   }
+  if (!definition->Descriptor().IsAutonomous()) {
+    exception_state.ThrowDOMException(
+        DOMExceptionCode::kInvalidStateError,
+        "Unable to attach ElementInternals to a customized built-in element.");
+    return nullptr;
+  }
   if (definition->DisableInternals()) {
     exception_state.ThrowDOMException(
         DOMExceptionCode::kInvalidStateError,

third_party/blink/web_tests/custom-elements/tentative/ElementInternals.html

+<!DOCTYPE html>
+<body>
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<script>
+test(() => {
+  class MyElement1 extends HTMLElement {}
+  customElements.define('my-element1', MyElement1);
+  const element = new MyElement1();
+  const internals = element.attachInternals();
+
+  assert_throws('InvalidStateError', () => { internals.setFormValue(''); });
+  assert_throws('InvalidStateError', () => { internals.form; });
+}, 'Form-related operations and attributes should throw InvalidStateErrors for' +
+     'non-form-associated custom elements.');
+</script>
+</body>

third_party/blink/web_tests/custom-elements/tentative/HTMLElement-attachInternals.html

@@ -30,6 +30,14 @@ test(() => {
   }, 'Parser - 2nd call');
 }, 'Successful attachInternals() and the second call.');
 
+test(() => {
+  class MyDiv extends HTMLDivElement {}
+  customElements.define('my-div', MyDiv, { extends: 'div' });
+  const customizedBuiltin = document.createElement('div', { is: 'my-div'});
+  assert_throws('InvalidStateError', () => { customizedBuiltin.attachInternals() });
+}, 'attachInternals() throws an InvalidStateError if it is called for ' +
+     'a customized built-in element');
+
 test(() => {
   const builtin = document.createElement('div');
   assert_throws('InvalidStateError', () => { builtin.attachInternals() });