Wordpress shortcode is not called - wordpress

Question

Okay, I have created a plugin and now want to provide shortcode to app.
Here is my only file in wp-content/plugins/my-plugin/my-plugin.php
<?php
/**
* Plugin Name: Latest Issue
* Author: Max Tsepkov
* Author URI: http://www.yogi.pw
*/
add_action('init', function() {
add_shortcode('my-plugin', function() {
// ... my code
return 'string';
});
});
I know that plugin is activated and the callback for init is called.
But the shortcode function is never get called.
I add text [my-plugin] to a widget, and it isn't replaced as well.
What do I do wrong? How to correctly register a shortcode?

Answer 1

I guess you PHP is at least 5.3, so you can make it work in a widget, you need to add this code.
add_filter('widget_text', 'do_shortcode');
I tested your code and it works.

Answer 2

Turned out, that some themes are not parsing shortcodes in widgets.
We can explicitly hook into theme filter and let it run shortcodes in widgets.
For details see https://wordpress.org/support/topic/how-to-make-shortcodes-work-in-a-widget
And there is no need for hook into init action. This code works:
<?php
/**
* Plugin Name: Latest Issue
* Author: Max Tsepkov
* Author URI: http://www.yogi.pw
*/
// Allow theme to parse shortcodes in widgets
add_filter('widget_text', 'do_shortcode');
add_shortcode('my-plugin', function() {
// ... my code
return 'string';
});