Bug 1812696 - Implement FormData constructor submitter parameter r=webidl,smaug

Also improve error messages for current submitter validations

Spec PR: https://github.com/whatwg/xhr/pull/366
WPT PR: https://github.com/web-platform-tests/wpt/pull/37895

Differential Revision: https://phabricator.services.mozilla.com/D167576

dom/base/FormData.cpp

@@ -10,6 +10,8 @@
 #include "mozilla/dom/Directory.h"
 #include "mozilla/dom/HTMLFormElement.h"
 #include "mozilla/Encoding.h"
+#include "nsGenericHTMLElement.h"
+#include "nsQueryObject.h"
 
 #include "MultipartBlobImpl.h"
 
@@ -298,12 +300,37 @@ JSObject* FormData::WrapObject(JSContext* aCx,
   return FormData_Binding::Wrap(aCx, this, aGivenProto);
 }
 
+// https://xhr.spec.whatwg.org/#dom-formdata
 /* static */
 already_AddRefed<FormData> FormData::Constructor(
     const GlobalObject& aGlobal,
-    const Optional<NonNull<HTMLFormElement> >& aFormElement, ErrorResult& aRv) {
-  RefPtr<FormData> formData = new FormData(aGlobal.GetAsSupports());
+    const Optional<NonNull<HTMLFormElement> >& aFormElement,
+    nsGenericHTMLElement* aSubmitter, ErrorResult& aRv) {
+  RefPtr<FormData> formData;
+  // 1. If form is given, then:
   if (aFormElement.WasPassed()) {
+    // 1.1. If submitter is non-null, then:
+    if (aSubmitter) {
+      nsCOMPtr<nsIFormControl> fc = do_QueryObject(aSubmitter);
+
+      // 1.1.1. If submitter is not a submit button, then throw a TypeError.
+      if (!fc || !fc->IsSubmitControl()) {
+        aRv.ThrowTypeError("The submitter is not a submit button.");
+        return nullptr;
+      }
+
+      // 1.1.2. If submitter's form owner is not this form element, then throw a
+      //      "NotFoundError" DOMException.
+      if (fc->GetForm() != &aFormElement.Value()) {
+        aRv.ThrowNotFoundError("The submitter is not owned by this form.");
+        return nullptr;
+      }
+    }
+
+    // 1.2. Let list be the result of constructing the entry list for form and
+    // submitter.
+    formData =
+        new FormData(aGlobal.GetAsSupports(), UTF_8_ENCODING, aSubmitter);
     aRv = aFormElement.Value().ConstructEntryList(formData);
     if (NS_WARN_IF(aRv.Failed())) {
       return nullptr;
@@ -312,6 +339,8 @@ already_AddRefed<FormData> FormData::Constructor(
     // Step 9. Return a shallow clone of entry list.
     // https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#constructing-form-data-set
     formData = formData->Clone();
+  } else {
+    formData = new FormData(aGlobal.GetAsSupports());
   }
 
   return formData.forget();

dom/base/FormData.h

@@ -12,6 +12,7 @@
 #include "mozilla/dom/HTMLFormSubmission.h"
 #include "mozilla/dom/File.h"
 #include "mozilla/dom/FormDataBinding.h"
+#include "nsGenericHTMLElement.h"
 #include "nsTArray.h"
 #include "nsWrapperCache.h"
 
@@ -69,7 +70,7 @@ class FormData final : public nsISupports,
   static already_AddRefed<FormData> Constructor(
       const GlobalObject& aGlobal,
       const Optional<NonNull<HTMLFormElement> >& aFormElement,
-      ErrorResult& aRv);
+      nsGenericHTMLElement* aSubmitter, ErrorResult& aRv);
 
   void Append(const nsAString& aName, const nsAString& aValue,
               ErrorResult& aRv);

dom/html/HTMLFormElement.cpp

@@ -296,7 +296,7 @@ void HTMLFormElement::RequestSubmit(nsGenericHTMLElement* aSubmitter,
     // 1.2. If submitter's form owner is not this form element, then throw a
     //      "NotFoundError" DOMException.
     if (fc->GetForm() != this) {
-      aRv.Throw(NS_ERROR_DOM_NOT_FOUND_ERR);
+      aRv.ThrowNotFoundError("The submitter is not owned by this form.");
       return;
     }
   }

dom/webidl/FormData.webidl

@@ -12,7 +12,7 @@ typedef (Blob or Directory or USVString) FormDataEntryValue;
 [Exposed=(Window,Worker)]
 interface FormData {
   [Throws]
-  constructor(optional HTMLFormElement form);
+  constructor(optional HTMLFormElement form, optional HTMLElement? submitter = null);
 
   [Throws]
   undefined append(USVString name, Blob value, optional USVString filename);

testing/web-platform/meta/xhr/formdata/constructor-submitter.html.ini

@@ -1,15 +0,0 @@
-[constructor-submitter.html]
-  [FormData construction should throw a TypeError if a non-null submitter is not a submit button]
-    expected: FAIL
-
-  [FormData construction should throw a 'NotFoundError' DOMException if a non-null submitter is not owned by the form]
-    expected: FAIL
-
-  [The constructed FormData object should contain an in-tree-order entry for a named submit button submitter]
-    expected: FAIL
-
-  [The constructed FormData object should contain in-tree-order entries for an activated Image Button submitter]
-    expected: FAIL
-
-  [The constructed FormData object should contain in-tree-order entries for an unactivated Image Button submitter]
-    expected: FAIL