Issue #3067889 by quietone: Boolean Field On and Off Label not Migrating

core/modules/field/src/Plugin/migrate/process/d7/FieldInstanceSettings.php

@@ -65,6 +65,16 @@ public function transform($value, MigrateExecutableInterface $migrate_executable
       $instance_settings['handler_settings'] = $field_settings['handler_settings'];
     }
 
+    // Get the labels for the list_boolean type.
+    if ($row->getSourceProperty('type') === 'list_boolean') {
+      if (isset($field_data['settings']['allowed_values'][1])) {
+        $instance_settings['on_label'] = $field_data['settings']['allowed_values'][1];
+      }
+      if (isset($field_data['settings']['allowed_values'][0])) {
+        $instance_settings['off_label'] = $field_data['settings']['allowed_values'][0];
+      }
+    }
+
     switch ($widget_type) {
       case 'image_image':
         $settings = $instance_settings;

core/modules/field/tests/src/Kernel/Migrate/d7/MigrateFieldInstanceTest.php

@@ -150,6 +150,13 @@ public function testFieldInstances() {
     $this->assertNull($name_field);
     $description_field = FieldConfig::load('taxonomy_term.test_vocabulary.description_field');
     $this->assertNull($description_field);
+
+    $boolean_field = FieldConfig::load('node.test_content_type.field_boolean');
+    $expected_settings = [
+      'on_label' => '1',
+      'off_label' => 'Off',
+    ];
+    $this->assertSame($expected_settings, $boolean_field->get('settings'));
   }
 
   /**