fix(pages): replace history for same-page action re-renders

Fixes #527

## Summary

Named actions no longer pollute history when they re-render the current page. #530 already removed `?actionName` from the committed URL; #531 still used `pushState` for every mutation, so each `useForm('/db?create')` / `action()` submit added another back-stack entry at `/db`.

- Same-document mutations use `replaceState` instead of `pushState`.
- `mutationCommitUrl()` prefers the server `pageData.url` when the action updates query params on the same path (e.g. `POST /books?delete` → `/books?page=2` still pushes once).

## Tests

Updated POST history expectations to `replaceState` when the browser URL already matches the committed page URL. Added coverage for URL-changing POSTs and repeated same-page named-action submits.

`vp test run packages/void/test/unit/pages-client.test.ts` — 69/69 passed.

Co-authored-by: froQ <sayhola@froq.me>

Author: cursoragent

packages/void/src/pages/navigation-engine.ts

@@ -26,6 +26,22 @@ function withoutActionKey(fetchUrl: string, pageUrl: string): string {
     : fetchUrl;
 }
 
+/** URL to commit after a page mutation (strip action keys, then prefer the server page URL). */
+function mutationCommitUrl(fetchUrl: string, pageUrl?: string): string {
+  if (!pageUrl) {
+    return withoutActionKey(fetchUrl, '');
+  }
+  const withoutKey = withoutActionKey(fetchUrl, pageUrl);
+  if (withoutKey !== fetchUrl) {
+    return withoutKey;
+  }
+  const fetchPathEnd = fetchUrl.indexOf('?');
+  const fetchPath = fetchPathEnd === -1 ? fetchUrl : fetchUrl.slice(0, fetchPathEnd);
+  const pagePathEnd = pageUrl.indexOf('?');
+  const pagePath = pagePathEnd === -1 ? pageUrl : pageUrl.slice(0, pagePathEnd);
+  return fetchPath === pagePath ? pageUrl : fetchUrl;
+}
+
 export type PageComponentModule = {
   default: unknown;
 };
@@ -835,7 +851,7 @@ export async function createPageNavigationEngine(
 
     if (method !== 'GET') {
       deferredRegistry.preserveValuesFrom(_committedDeferredRegistry, pageData);
-      commitTarget.fetchUrl = withoutActionKey(fetchUrl, pageData.url);
+      commitTarget.fetchUrl = mutationCommitUrl(fetchUrl, pageData.url);
     }
 
     const [component, layouts] = await Promise.race([
@@ -923,7 +939,12 @@ export async function createPageNavigationEngine(
       // preserveState only controls component state; back/forward traversal already moved history.
       if (!options._popstate) {
         const historyUrl = commitTarget.fetchUrl + commitTarget.hash;
-        scrollRestoration.writeHistory(historyUrl, !!options.replace);
+        const resource = getResource();
+        const currentDocumentUrl = window.location.pathname + window.location.search;
+        const replaceHistory =
+          !!options.replace ||
+          (resource.method !== 'GET' && historyUrl === currentDocumentUrl + commitTarget.hash);
+        scrollRestoration.writeHistory(historyUrl, replaceHistory);
       }
       scrollRestoration.commit();
 

packages/void/test/unit/pages-client.test.ts

@@ -514,8 +514,11 @@ describe('createVoidRouter', () => {
     ['/books?delete', '/books', '/books'],
     ['/books?page=2', '/books?page=2', '/books?page=2'],
     ['/books?a&b', '/books?a&b', '/books?a&b'],
-  ])('writes POST %s with page URL %s to history as %s', async (url, pageUrl, historyUrl) => {
+  ])('replaces history for POST %s with page URL %s as %s', async (url, pageUrl, historyUrl) => {
     stubClientGlobals();
+    const historyLocation = new URL(historyUrl, 'http://localhost');
+    window.location.pathname = historyLocation.pathname;
+    window.location.search = historyLocation.search;
     vi.stubGlobal(
       'fetch',
       vi.fn(async () => pageJson({ component: 'home', props: {}, url: pageUrl, errors: null })),
@@ -524,7 +527,44 @@ describe('createVoidRouter', () => {
 
     await router.visit(url, { method: 'POST' });
 
-    expect(history.pushState).toHaveBeenCalledWith(expect.anything(), '', historyUrl);
+    expect(history.replaceState).toHaveBeenCalledWith(expect.anything(), '', historyUrl);
+    expect(history.pushState).not.toHaveBeenCalled();
+  });
+
+  it('pushes history when a POST changes the page URL', async () => {
+    stubClientGlobals();
+    window.location.pathname = '/books';
+    window.location.search = '';
+    vi.stubGlobal(
+      'fetch',
+      vi.fn(async () =>
+        pageJson({ component: 'home', props: {}, url: '/books?page=2', errors: null }),
+      ),
+    );
+    const { router } = await createTestRouter();
+
+    await router.visit('/books?delete', { method: 'POST' });
+
+    expect(history.pushState).toHaveBeenCalledWith(expect.anything(), '', '/books?page=2');
+    expect(history.replaceState).not.toHaveBeenCalled();
+  });
+
+  it('does not grow history on repeated same-page named action submits', async () => {
+    stubClientGlobals();
+    window.location.pathname = '/db';
+    window.location.search = '';
+    vi.stubGlobal(
+      'fetch',
+      vi.fn(async () => pageJson({ component: 'home', props: {}, url: '/db', errors: null })),
+    );
+    const { router } = await createTestRouter();
+
+    await router.visit('/db?create', { method: 'POST' });
+    await router.visit('/db?create', { method: 'POST' });
+
+    expect(history.pushState).not.toHaveBeenCalled();
+    expect(history.replaceState).toHaveBeenCalledTimes(2);
+    expect(history.replaceState).toHaveBeenLastCalledWith(expect.anything(), '', '/db');
   });
 
   it('runs navigation listeners for same-page hash visits', async () => {