Respect morphing and scroll preservation settings when handling form …

…errors

Turbo will render 422 responses to allow handling form errors. A common scenario
in Rails is to render those setting the satus like:

```
render "edit", status: :unprocessable_entity
```

This change will consider such operations a "page refresh" and will also consider
the scroll directive.

src/core/drive/navigator.js

@@ -99,7 +99,9 @@ export class Navigator {
       } else {
         await this.view.renderPage(snapshot, false, true, this.currentVisit)
       }
-      this.view.scrollToTop()
+      if(!snapshot.shouldPreserveScrollPosition) {
+        this.view.scrollToTop()
+      }
       this.view.clearSnapshotCache()
     }
   }

src/core/drive/page_view.js

@@ -60,7 +60,7 @@ export class PageView extends View {
   }
 
   isPageRefresh(visit) {
-    return visit && this.lastRenderedLocation.href === visit.location.href
+    return !visit || this.lastRenderedLocation.href === visit.location.href
   }
 
   get snapshot() {

src/tests/fixtures/page_refresh.html

@@ -49,6 +49,13 @@ <h3>Element with Stimulus controller</h3>
       <input id="form-submit" type="submit" value="form[method=post]">
     </form>
 
+    <div id="reject">
+      <form class="unprocessable_entity" action="/__turbo/reject" method="post" style="margin-top:100vh">
+        <input type="hidden" name="status" value="422">
+        <input type="submit">
+      </form>
+    </div>
+
     <div id="container">
     </div>
   </body>

src/tests/functional/page_refresh_tests.js

@@ -1,6 +1,9 @@
 import { test, expect } from "@playwright/test"
+import { assert } from "chai"
 import {
+  hasSelector,
   nextBeat,
+  nextBody,
   nextEventNamed,
   nextEventOnTarget,
   noNextEventOnTarget,
@@ -53,7 +56,7 @@ test("don't refresh frames contained in [data-turbo-permanent] elements", async
   expect(await noNextEventOnTarget(page, "refresh-reload", "turbo:before-frame-morph")).toBeTruthy()
 })
 
-test("frames marked with refresh='morph' are excluded from full page morphing", async ({ page }) => {
+test("remote frames excluded from full page morphing", async ({ page }) => {
   await page.goto("/src/tests/fixtures/page_refresh.html")
 
   await page.evaluate(() => document.getElementById("remote-frame").setAttribute("data-modified", "true"))
@@ -126,6 +129,18 @@ test("it preserves data-turbo-permanent elements that don't match when their ids
   await expect(page.locator("#preserve-me")).toHaveText("Preserve me, I have a family!")
 })
 
+test("renders unprocessable entity responses with morphing", async ({ page }) => {
+  await page.goto("/src/tests/fixtures/page_refresh.html")
+
+  await page.click("#reject form.unprocessable_entity input[type=submit]")
+  await nextEventNamed(page, "turbo:render", { renderMethod: "morph" })
+  await nextBody(page)
+
+  const title = await page.locator("h1")
+  assert.equal(await title.textContent(), "Unprocessable Entity", "renders the response HTML")
+  assert.notOk(await hasSelector(page, "#frame form.reject"), "replaces entire page")
+})
+
 async function assertPageScroll(page, top, left) {
   const [scrollTop, scrollLeft] = await page.evaluate(() => {
     return [