lib/components/web/form/fields/Taxonomy.php
public function generate()
    {
        $this->type = 'dropDownList';
        $baseOptions = [];
        if (!$this->modelField->taxonomy->required) {
            $baseOptions[''] = '';
        }
        $this->options = array_merge($baseOptions, ArrayHelper::map($this->modelField->taxonomy->taxonomies, 'id', 'name'));

        if ($this->modelField->taxonomy->multiple) {
            $this->htmlOptions['multiple'] = true;
        }

        return parent::generate();
    }
public function generate()
    {
        $this->type = 'dropDownList';
        $baseOptions = [];
        if (!$this->modelField->taxonomy->required) {
            $baseOptions[''] = '';
        }
        $this->options = array_merge($baseOptions, ArrayHelper::map($this->modelField->taxonomy->taxonomies, 'id', 'name'));

        if ($this->modelField->taxonomy->multiple) {
            $this->htmlOptions['multiple'] = true;
        }

        return parent::generate();
    }
{@inheritdocs}.