Ticket #44347: 44347.includes.user.php.diff

user.php

@@ -206 +206 @@
         }
 
         /**
+         * Additional checks for cross-referenced email and username among existing accounts.
+         * Prevent using existing email address as username and vice versa.
+         * Do not allow an existing email address to be used as a username of the new account.
+         * Do not allow an existing username to be used as the email address of the new account.
+         */
+
+        // Check if username is being used as the email address of another account.
+        if ( email_exists( $user->user_login ) ) {
+                $errors->add( 'email_exists_as_user_login', __( '<strong>ERROR</strong>: This username is invalid because it is already the email address of another account.' ) );
+        }
+
+        // Check if email address is being used as the username of another account.
+
+        /**
+         * Adding new user.
+         */
+        if ( ! $update ) {
+                if ( username_exists( $user->user_email ) ) {
+                        $errors->add( 'username_exists', __( '<strong>ERROR</strong>: This email address cannot be used because it is already the username of another account.' ) );
+                }
+        } else {
+                /**
+                 * Updating existing user.
+                 *
+                 * $owner_id false | int. If no user is found $owner_id is false. Otherwise returns user ID.
+                 */
+                $owner_id = username_exists( $user->user_email );
+                if ( $owner_id && ( $owner_id !== $user->ID ) ) {
+                        $errors->add( 'username_exists', __( '<strong>ERROR</strong>: This email address cannot be used because it is already the username of another account.' ) );
+                }
+        }
+
+        /**
          * Fires before user profile update errors are returned.
          *
          * @since 2.8.0