Alter AccountForms instead of just registration form when using this module.

+1 for this.

+++ b/email_registration.module
@@ -119,13 +120,18 @@ function email_registration_cleanup_username($name) {
+  $form_object = $form_state->getFormObject();
+  $class = AccountForm::class;
+  if (is_subclass_of($form_object, $class) || is_a($form_object, $class)) {
...
+  }
 }

This could probably have been done by simply checking the form_id, also a little safer in case someone is extending/using the AccountForm for anything else.

Please update summary why that change could be useful

Registration form defined in user entity annotation so could be overriden but I do not like non-specific hook_form_alter() cos it will fire for every form on site

+++ b/email_registration.module
@@ -119,13 +120,18 @@ function email_registration_cleanup_username($name) {
-  $form['account']['mail']['#title'] = t('E-mail');
...
+    $form['account']['mail']['#title'] = t('E-mail');

will be affected by #2864902: Update "e-mail" to "email" across all files

Here is a patch which implements hook_user_form_alter() instead of hook_form_alter().

New patch since the previous one failed to apply.

It looks great except I'm not sure that Registration Types module & other custom implementations will not inherit their forms from the core's class

The patch remove the email_registration_form_user_register_form_alter function and add email_registration_form_user_form_alter function, but the user form alter already exist line 181. It creates an error

needs work for #13

Only changing the form ID to Form Base will make this module work with form mode manager.

Change hook to BASE_FORM to support form mode manager module.

This is a straight reroll of #16 since DrupalCI seems to be mad about something in that one.

OK, let's try this again :) Still just a reroll of #16 to remove fuzz of one line.

OK - now fixed. Thanks!

This issue seems to have caused a regression - see #3024558: Username regenerated improperly after rc6 release.