Update the FormData constructor to allow providing a submitter (#35066)

Signed-off-by: Shane Handley <shanehandley@fastmail.com>

components/script/dom/formdata.rs

@@ -20,7 +20,12 @@ use crate::dom::bindings::str::{DOMString, USVString};
 use crate::dom::blob::Blob;
 use crate::dom::file::File;
 use crate::dom::globalscope::GlobalScope;
-use crate::dom::htmlformelement::{FormDatum, FormDatumValue, HTMLFormElement};
+use crate::dom::htmlbuttonelement::HTMLButtonElement;
+use crate::dom::htmlelement::HTMLElement;
+use crate::dom::htmlformelement::{
+    FormDatum, FormDatumValue, FormSubmitterElement, HTMLFormElement,
+};
+use crate::dom::htmlinputelement::HTMLInputElement;
 use crate::script_runtime::CanGc;
 
 #[dom_struct]
@@ -70,20 +75,60 @@ impl FormData {
 
 impl FormDataMethods<crate::DomTypeHolder> for FormData {
     // https://xhr.spec.whatwg.org/#dom-formdata
-    fn Constructor(
+    fn Constructor<'a>(
         global: &GlobalScope,
         proto: Option<HandleObject>,
         can_gc: CanGc,
-        form: Option<&HTMLFormElement>,
+        form: Option<&'a HTMLFormElement>,
+        submitter: Option<&'a HTMLElement>,
     ) -> Fallible<DomRoot<FormData>> {
+        // Helper to validate the submitter
+        fn validate_submitter<'b>(
+            submitter: &'b HTMLElement,
+            form: &'b HTMLFormElement,
+        ) -> Result<FormSubmitterElement<'b>, Error> {
+            let submit_button = submitter
+                .downcast::<HTMLButtonElement>()
+                .map(FormSubmitterElement::Button)
+                .or_else(|| {
+                    submitter
+                        .downcast::<HTMLInputElement>()
+                        .map(FormSubmitterElement::Input)
+                })
+                .ok_or(Error::Type(
+                    "submitter is not a form submitter element".to_string(),
+                ))?;
+
+            // Step 1.1.1. If submitter is not a submit button, then throw a TypeError.
+            if !submit_button.is_submit_button() {
+                return Err(Error::Type("submitter is not a submit button".to_string()));
+            }
+
+            // Step 1.1.2. If submitter’s form owner is not form, then throw a "NotFoundError"
+            // DOMException.
+            if !matches!(submit_button.form_owner(), Some(owner) if *owner == *form) {
+                return Err(Error::NotFound);
+            }
+
+            Ok(submit_button)
+        }
+
+        // Step 1. If form is given, then:
         if let Some(opt_form) = form {
-            return match opt_form.get_form_dataset(None, None, can_gc) {
+            // Step 1.1. If submitter is non-null, then:
+            let submitter_element = submitter
+                .map(|s| validate_submitter(s, opt_form))
+                .transpose()?;
+
+            // Step 1.2. Let list be the result of constructing the entry list for form and submitter.
+            return match opt_form.get_form_dataset(submitter_element, None, can_gc) {
                 Some(form_datums) => Ok(FormData::new_with_proto(
                     Some(form_datums),
                     global,
                     proto,
                     can_gc,
                 )),
+                // Step 1.3. If list is null, then throw an "InvalidStateError" DOMException.
                 None => Err(Error::InvalidState),
             };
         }

components/script/dom/htmlformelement.rs

@@ -1475,7 +1475,7 @@ impl FormSubmitterElement<'_> {
     }
 
     // https://html.spec.whatwg.org/multipage/#concept-submit-button
-    fn is_submit_button(&self) -> bool {
+    pub(crate) fn is_submit_button(&self) -> bool {
         match *self {
             // https://html.spec.whatwg.org/multipage/#image-button-state-(type=image)
             // https://html.spec.whatwg.org/multipage/#submit-button-state-(type=submit)
@@ -1487,7 +1487,7 @@ impl FormSubmitterElement<'_> {
     }
 
     // https://html.spec.whatwg.org/multipage/#form-owner
-    fn form_owner(&self) -> Option<DomRoot<HTMLFormElement>> {
+    pub(crate) fn form_owner(&self) -> Option<DomRoot<HTMLFormElement>> {
         match *self {
             FormSubmitterElement::Button(button_el) => button_el.form_owner(),
             FormSubmitterElement::Input(input_el) => input_el.form_owner(),

components/script/dom/webidls/FormData.webidl

@@ -10,7 +10,7 @@ typedef (File or USVString) FormDataEntryValue;
 
 [Exposed=(Window,Worker)]
 interface FormData {
-  [Throws] constructor(optional HTMLFormElement form);
+  [Throws] constructor(optional HTMLFormElement form, optional HTMLElement? submitter = null);
   undefined append(USVString name, USVString value);
   undefined append(USVString name, Blob value, optional USVString filename);
   undefined delete(USVString name);