fix(service-worker): only consider GET requests as navigation requests (#47263)

Previously, the criteria for determining if a request was a
[navigation request][1] did not account for the request method. This
incorrectly identified HTML form submit POST requests as navigation
requests and served `index.html` instead of passing them through to the
server, thus breaking the form submission.

This commit fixes this by ensuring that only GET requests are considered
navigation requests.

> **Note**
> HTML forms with their method set to `GET` will still be affected by
> the issue. This is not a big concern, because using `GET` for form
> submission is quite uncommon and generally discouraged (due to
> limitations and security considerations).

[1]: https://angular.io/guide/service-worker-config#handling-navigation-requests

Fixes #36368

PR Close #47263

aio/content/guide/service-worker-config.md

@@ -376,6 +376,7 @@ This optional section enables you to specify a custom list of URLs that will be
 The ServiceWorker redirects navigation requests that don't match any `asset` or `data` group to the specified [index file](#index-file).
 A request is considered to be a navigation request if:
 
+*   Its [method](https://developer.mozilla.org/docs/Web/API/Request/method) is `GET`
 *   Its [mode](https://developer.mozilla.org/docs/Web/API/Request/mode) is `navigation`
 *   It accepts a `text/html` response as determined by the value of the `Accept` header
 *   Its URL matches the following criteria:

packages/service-worker/worker/src/app-version.ts

@@ -203,10 +203,10 @@ export class AppVersion implements UpdateSource {
 
   /**
    * Determine whether the request is a navigation request.
-   * Takes into account: Request mode, `Accept` header, `navigationUrls` patterns.
+   * Takes into account: Request method and mode, `Accept` header, `navigationUrls` patterns.
    */
   isNavigationRequest(req: Request): boolean {
-    if (req.mode !== 'navigate') {
+    if (req.method !== 'GET' || req.mode !== 'navigate') {
       return false;
     }
 

packages/service-worker/worker/test/happy_spec.ts

@@ -1704,6 +1704,14 @@ describe('Driver', () => {
       server.assertNoOtherRequests();
     });
 
+    it('does not redirect to index on a non-GET request', async () => {
+      expect(await navRequest('/baz', {method: 'POST'})).toBeNull();
+      server.assertSawRequestFor('/baz');
+
+      expect(await navRequest('/qux', {method: 'PUT'})).toBeNull();
+      server.assertSawRequestFor('/qux');
+    });
+
     it('does not redirect to index on a non-navigation request', async () => {
       expect(await navRequest('/baz', {mode: undefined})).toBeNull();
       server.assertSawRequestFor('/baz');