Show sharing buttons, e.g. from Jetpack

functions.php

<?php
// Show sharing buttons, e.g. from Jetpack
// https://wordpress.org/support/topic/jetpack-sharing-options-showing-in-widget/
// TODO: Rewrite code as filter hook

function form($instance) {
        ...
	<p>
 		<label for="<?php echo $this->get_field_id("hide_social_buttons"); ?>">
 			<input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id("hide_social_buttons"); ?>" name="<?php echo $this->get_field_name("hide_social_buttons"); ?>"<?php checked( (bool) $instance["hide_social_buttons"], true ); ?> />
 				<?php _e( 'Hide social buttons in widget output',TEXTDOMAIN ); ?>
 		</label>
 	</p>
        ...
}

class Widget extends \WP_Widget {
  ...
  
	/**
	 * Apply the_content filter for excerpt
	 * This should show sharing buttons which comes with other widgets in the widget output in the same way as on the main content
	 *
     * @param  string The HTML with other applied excerpt filters
     *
	 * @return string If option hide_social_buttons is unchecked applay the_content filter
     *
     * @since 4.6
	 */	
	function apply_the_excerpt($text) {
		$ret = "";
 		if (isset($this->instance["hide_social_buttons"]) && $this->instance["hide_social_buttons"])
 			$ret = $text;
 		else
 			$ret = apply_filters('the_content', $text);
		return $ret;
  }
  ...
}