Fix back redirection from Woo connect switch user flow

client/layout/masterbar/woo.jsx

@@ -9,10 +9,32 @@ import './typekit';
 import './woo.scss';
 
 const WooOauthMasterbar = () => {
- function onClick() {
+ function goBack() {
  window.history.back();
  }
 
+ function onClick() {
+ // When the URL that initiates login is the connection page (during a switch user flow),
+ // we need to find the deeply nested home_url parameter to redirect back to the
+ // extensions page. This is because otherwise history back() will just redirect back to
+ // login as we still don't have a user. At any stage if we're not able to find a
+ // parameter, we give up and go back.
+ try {
+ const url = new URL( window.location.href );
+ const redirectURL = new URL( url.searchParams.get( 'redirect_to' ) );
+ const siteURL = new URL( redirectURL.searchParams.get( 'redirect_uri' ) );
+ // We just get a path here, so we construct an example URL.
+ const nextURL = new URL( 'http://example.com' + siteURL.searchParams.get( 'next' ) );
+ // Validate the URL and get it back as a string.
+ const homeURL = new URL( nextURL.searchParams.get( 'home_url' ) ).toString();
+ // add the extensions page path.
+ const finalRedirectURL = `${ homeURL }wp-admin/admin.php?page=wc-admin&tab=my-subscriptions&path=%2Fextensions`;
+ window.location = finalRedirectURL;
+ } catch {
+ goBack();
+ }
+ }
+
  const backNav = (
  <li className="masterbar__woo-nav-item">
  <Button className="masterbar__login-back-link" onClick={ onClick }>