Add setting to hide username on the login checkout pane

modules/checkout/config/schema/commerce_checkout.schema.yml

@@ -76,6 +76,9 @@ commerce_checkout.commerce_checkout_pane.login:
     allow_registration:
       type: boolean
       label: 'Allow registration'
+    email_only:
+      type: boolean
+      label: 'E-Mail only registration'
 
 commerce_checkout_pane_configuration:
   type: mapping

modules/checkout/src/Plugin/Commerce/CheckoutPane/Login.php

@@ -116,6 +116,7 @@ public function defaultConfiguration() {
     return [
       'allow_guest_checkout' => TRUE,
       'allow_registration' => FALSE,
+      'email_only' => FALSE,
     ] + parent::defaultConfiguration();
   }
 
@@ -136,6 +137,10 @@ public function buildConfigurationSummary() {
       }
     }
 
+    if (!empty($this->configuration['email_only'])) {
+      $summary .= '<br>' . $this->t('Use E-mail only for registration and login');
+    }
+
     return $summary;
   }
 
@@ -160,6 +165,13 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
       ],
     ];
 
+    $form['email_only'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Use E-Mail only for registration and login'),
+      '#description' => $this->t('If checked, the name field will not be shown and the e-mail will be used as username.'),
+      '#default_value' => $this->configuration['email_only'],
+    ];
+
     return $form;
   }
 
@@ -173,6 +185,7 @@ public function submitConfigurationForm(array &$form, FormStateInterface $form_s
       $values = $form_state->getValue($form['#parents']);
       $this->configuration['allow_guest_checkout'] = !empty($values['allow_guest_checkout']);
       $this->configuration['allow_registration'] = !empty($values['allow_registration']);
+      $this->configuration['email_only'] = !empty($values['email_only']);
     }
   }
 
@@ -201,7 +214,7 @@ public function buildPaneForm(array $pane_form, FormStateInterface $form_state,
     ];
     $pane_form['returning_customer']['name'] = [
       '#type' => 'textfield',
-      '#title' => $this->t('Username'),
+      '#title' => $this->configuration['email_only'] ? $this->t('E-Mail') : $this->t('Username'),
       '#size' => 60,
       '#maxlength' => USERNAME_MAX_LENGTH,
       '#attributes' => [
@@ -270,6 +283,7 @@ public function buildPaneForm(array $pane_form, FormStateInterface $form_state,
       '#maxlength' => USERNAME_MAX_LENGTH,
       '#description' => $this->t("Several special characters are allowed, including space, period (.), hyphen (-), apostrophe ('), underscore (_), and the @ sign."),
       '#required' => FALSE,
+      '#access' => empty($this->configuration['email_only']),
       '#attributes' => [
         'class' => ['username'],
         'autocorrect' => 'off',
@@ -340,13 +354,13 @@ public function validatePaneForm(array &$pane_form, FormStateInterface $form_sta
 
       case 'register':
         $email = $values['register']['mail'];
-        $username = $values['register']['name'];
+        $username = $this->configuration['email_only'] ? $values['register']['mail'] : $values['register']['name'];
         $password = trim($values['register']['password']);
         if (empty($email)) {
           $form_state->setError($pane_form['register']['mail'], $this->t('Email field is required.'));
           return;
         }
-        if (empty($username)) {
+        if (empty($this->configuration['email_only']) && empty($username)) {
           $form_state->setError($pane_form['register']['name'], $this->t('Username field is required.'));
           return;
         }