Display user ID instead of user_login

features/super-admin.feature

@@ -24,12 +24,6 @@ Feature: Manage super admins associated with a multisite instance
       superadmin
       """
 
-    When I run `wp super-admin list --format=ids`
-    Then STDOUT should be:
-      """
-      admin superadmin
-      """
-
     When I try `wp super-admin add superadmin`
     Then STDERR should be:
       """
@@ -186,6 +180,22 @@ Feature: Manage super admins associated with a multisite instance
     And STDOUT should be empty
     And the return code should be 1
 
+  Scenario: List super admins in ids format.
+    Given a WP multisite installation
+
+    When I run `wp user get admin --field=ID`
+    And save STDOUT as {USER_1}
+
+    When I run `wp user create admin2 admin2@example.com --porcelain`
+    And save STDOUT as {USER_2}
+
+    When I run `wp super-admin add admin2`
+    And I run `wp super-admin list --format=ids`
+    Then STDOUT should be:
+      """
+      {USER_1} {USER_2}
+      """
+
   Scenario: Manage a super admin user_login 'admin'
     Given a WP multisite installation
 

src/Super_Admin_Command.php

@@ -81,7 +81,13 @@ public function list_subcommand( $_, $assoc_args ) {
 
 			if ( ! empty( $assoc_args['format'] ) && 'ids' === $assoc_args['format'] ) {
 				$formatter = new \WP_CLI\Formatter( $assoc_args );
-				$formatter->display_items( wp_list_pluck( $output_users, 'user_login' ) );
+
+				$user_ids = [];
+				foreach ( $super_admins as $user_login ) {
+					$user_obj   = get_user_by( 'login', $user_login );
+					$user_ids[] = $user_obj->ID;
+				}
+				$formatter->display_items( $user_ids );
 			} else {
 				$formatter = new \WP_CLI\Formatter( $assoc_args, $this->fields );
 				$formatter->display_items( $output_users );