ReactDOM.requestFormReset

This adds a React DOM method called requestFormReset that schedules a
form reset to occur when the current transition completes.

Internally, it's the same method that's called automatically whenever
a form action is submitted. It only affects uncontrolled form inputs.
See facebook#28804 for details.

The reason for the public API is so UI libraries can implement their
own action-based APIs and maintain the form-resetting behavior,
something like this:

```js
function onSubmit(event) {
  // Disable default form submission behavior
  event.preventDefault();
  const form = event.target;
  startTransition(async () => {
    // Request the form to reset once the action
    // has completed
    requestFormReset(form);

    // Call the user-provided action prop
    await action(new FormData(form));
  })
}
```

packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js

@@ -1954,13 +1954,19 @@ function flushSyncWork() {
 }
 
 function requestFormReset(form: HTMLFormElement) {
-  previousDispatcher.r(/* requestFormReset */ form);
   const formInst = getInstanceFromNodeDOMTree(form);
-  if (formInst !== null) {
+  if (
+    formInst !== null &&
+    formInst.tag === HostComponent &&
+    formInst.type === 'form'
+  ) {
     requestFormResetOnFiber(formInst);
   } else {
-    // TODO: What if none of the dispatchers find a matching form instance?
-    // Should we detect this in dev and warn?
+    // This form was either not rendered by this React renderer (or it's an
+    // invalid type). Try the next one.
+    //
+    // The last implementation in the sequence will throw an error.
+    previousDispatcher.r(/* requestFormReset */ form);
   }
 }
 

packages/react-dom/src/ReactDOMSharedInternals.js

@@ -29,9 +29,16 @@ export type ReactDOMInternalsDev = ReactDOMInternals & {
 
 function noop() {}
 
+function requestFormReset(element: HTMLFormElement) {
+  throw new Error(
+    'Invalid form element. requestFormReset must be passed a form that was ' +
+      'rendered by React.',
+  );
+}
+
 const DefaultDispatcher: HostDispatcher = {
   f /* flushSyncWork */: noop,
-  r /* requestFormReset */: noop,
+  r /* requestFormReset */: requestFormReset,
   D /* prefetchDNS */: noop,
   C /* preconnect */: noop,
   L /* preload */: noop,