Shortcode not appearing when used as post content in wp_insert_post() or possibly, shortcode not being registered at all

Question

I have a plugin which creates a page upon activation and then removes it on deactivation. As part of the page creation, I wanted to use a shortcode in the post content, so I added a shortcode with add_shortcode() first.

For debug purposes, I immediately test the shortcode with shortcode_exists() and print out an appropriate log statement. The logs indicate that the shortcode exists. On the page automatically created, it just shows the shortcode name [myplugin_reference]. Even if I manually create a page and insert the shortcode, I get the same result.

I even installed a simple plugin - JSM's Show Registered Shortcodes which shows a list of registered shortcodes, and my shortcode isn't in the list.

Here is my code:

function install_myplugin() {
    add_shortcode( 'myplugin_reference', 'myplugin_shortcode_reference' );
    if ( shortcode_exists( 'myplugin_reference' ) ) {
        error_log( 'Shortcode "myplugin_reference" added successfully' );
    } else {
        error_log( 'Shortcode "myplugin_reference" not added' );
    }

    $templates = get_page_templates();
    $post      = array(
        'post_title'   => __( 'Thank You', 'myplugin-payment-gateway' ),
        'post_content' => '[myplugin_reference]',
        'post_status'  => 'publish',
        'post_name'    => 'myplugin-thank-you',
        'post_type'    => 'page'
    );

    if ( isset( $templates['Full width'] ) ) {
        $post['page_template'] = $templates['Full width'];
    }

    $page_id = wp_insert_post( $post, true );
    add_option( 'myplugin_thankyou_page_id', $page_id );
}

function uninstall_myplugin() {
    $page_id = get_option( 'myplugin_thankyou_page_id' );
    if ( $page_id ) {
        wp_delete_post( $page_id, true );
        delete_option( 'myplugin_thankyou_page_id' );
    }
    if ( shortcode_exists( 'myplugin_reference' ) ) {
        remove_shortcode( 'myplugin_reference' );
    }
}

function myplugin_shortcode_reference() {
    wp_enqueue_script( 'jquery' );

    ob_start();
    ?>
    <span id="payment-ref"></span>
    <script type="text/javascript">
        jQuery(function($) {
            let params = {},
                paramPairs = (window.location.search).replace(/^\?/, '').split("&");

            // get querystring params
            paramPairs.reduce((acc, current) => {
                const nameValue = current.split("=");
                return params[nameValue[0]] = decodeURIComponent(nameValue[1]);
            }, "");

            if (!!params.reference) {
                $('#payment-ref').html(params.reference);
            }
        });
    </script>
    <?php
    $output = ob_get_contents();
    ob_end_clean();

    return $output;
}

// Activation, Deactivation hooks
register_activation_hook( __FILE__, 'install_myplugin' );
register_deactivation_hook( __FILE__, 'uninstall_myplugin' );

And this is all that appears on the page:

Answer 1

You're only registering the shortcode on activation. add_shortcode() is not persistent, and since shortcodes are parsed on output, the shortcode needs to be registered on every request. So you need to move add_shortcode() outside of the activation hook:

function install_myplugin() {
    // ...
}

function uninstall_myplugin() {
    // ...
}

function myplugin_shortcode_reference() {
    // ...
}

// Activation, Deactivation hooks
register_activation_hook( __FILE__, 'install_myplugin' );
register_deactivation_hook( __FILE__, 'uninstall_myplugin' );
add_shortcode( 'myplugin_reference', 'myplugin_shortcode_reference' );