Multisite Update Check when only activated on subsite

[jakejackson1]

Multisite won't check for updates if the plugin isn't activated on the primary site of the multisite. The Easy Digital Downloads update module does a check on the Plugins admin page of an active subsite, but the admins will need to visit that page for an update check to occur. You see this with any plugin that receives updates from a source outside wp.org, including Gravity Forms and its extensions.

[jakejackson1]

Partial success with this snippet:

/**
 * Show upgrade notice on Network Admin if plugin is not network activated
 */
add_action( 'added_option', function ( $option, $value ) {
	if ( is_network_admin() || ! is_multisite() ) {
		return $value;
	}

	if ( strpos( $option, 'edd_sl_' ) !== 0 ) {
		return $value;
	}

	if ( ! isset( $value['timeout'], $value['value'] ) ) {
		return $value;
	}

	$update_info = json_decode( $value['value'] );
	if ( strpos( $update_info->slug, 'gravity-pdf' ) !== 0 ) {
		return $value;
	}

	/* force the network plugins to get updated */
	$_transient_data = get_site_transient( 'update_plugins' );

	$plugins = get_plugins();

	// @TODO - handle case where the transient data is false

	if ( $_transient_data !== false && $update_info !== null && is_object( $update_info ) && isset( $update_info->new_version ) && isset( $plugins[ $update_info->id ] ) ) {
		if ( version_compare( $plugins[ $update_info->id ]['Version'], $update_info->new_version, '<' ) ) {
			$_transient_data->response[ $update_info->id ] = $update_info;
			unset( $_transient_data->no_update[ $update_info->id ] );
		} else {
			// Populating the no_update information is required to support auto-updates in WordPress 5.5.
			$_transient_data->no_update[ $update_info->id ] = $update_info;
			unset( $_transient_data->response[ $update_info->id ] );
		}

		set_site_transient( 'update_plugins', $_transient_data );
	}

}, 10, 2 );

There are a few issues that would need addressing:

1. Ensure the subsite the plugin is active on runs a scheduled update check
2. If the network doesn't have anything saved in the update_plugins transient nothing happens
3. Extending EDD licensing class would make this work easier
4. The Network Admin won't show the changelog