Source

File: wp-includes/class-wp-customize-widgets.php

public function get_setting_args( $id, $overrides = array() ) {
		$args = array(
			'type'       => 'option',
			'capability' => 'edit_theme_options',
			'default'    => array(),
		);

		if ( preg_match( $this->setting_id_patterns['sidebar_widgets'], $id, $matches ) ) {
			$args['sanitize_callback']    = array( $this, 'sanitize_sidebar_widgets' );
			$args['sanitize_js_callback'] = array( $this, 'sanitize_sidebar_widgets_js_instance' );
			$args['transport']            = current_theme_supports( 'customize-selective-refresh-widgets' ) ? 'postMessage' : 'refresh';
		} elseif ( preg_match( $this->setting_id_patterns['widget_instance'], $id, $matches ) ) {
			$args['sanitize_callback']    = array( $this, 'sanitize_widget_instance' );
			$args['sanitize_js_callback'] = array( $this, 'sanitize_widget_js_instance' );
			$args['transport']            = $this->is_widget_selective_refreshable( $matches['id_base'] ) ? 'postMessage' : 'refresh';
		}

		$args = array_merge( $args, $overrides );

		/**
		 * Filters the common arguments supplied when constructing a Customizer setting.
		 *
		 * @since 3.9.0
		 *
		 * @see WP_Customize_Setting
		 *
		 * @param array  $args Array of Customizer setting arguments.
		 * @param string $id   Widget setting ID.
		 */
		return apply_filters( 'widget_customizer_setting_args', $args, $id );
	}