Fix: Bug Affecting Widgets without description

[jorgefilipecosta]

Description

Fixes: #14552

We were not checking in the widget description was set and on widgets, without description, an undefined notice was being thrown.

How has this been tested?

I installed the AnsPress Question Answer plugin: https://wordpress.org/plugins/anspress-question-answer.
I created a new page and verified and checked Undefined notice was not being thrown in the PHP code. In master, a notice should appear.

[aduth]

In what way is this change related to the fix?

[jorgefilipecosta]

During these changes, I noticed I missed to pass a description when I added support some simple call back widgets.
But it is not directly related to these changes. I separated this change to other PR #14615.

[aduth]

Alternative test (I'd created before this pull request):

1. Ensure define( 'WP_DEBUG', true ); in wp-config.php
2. Add the following as wp-content/mu-plugins/custom-widget.php:

<?php

class Custom_Widget extends WP_Widget {
	public function __construct() {
		parent::__construct( 'Custom_Widget', 'Custom Widget' );
	}

	public function widget( $args, $instance ) {
	}

	public function form( $instance ) {
	}

	public function update( $new_instance, $old_instance ) {
		return $new_instance;
	}
}

add_action( 'init', function() {
	register_widget( 'Custom_Widget' );
} );

3. Navigate to Posts > Add New

The PHP warning notice is no longer shown after these changes.

Can you confirm: Prior to this change, description was passed as an empty string when not defined by the widget. It is now passed as null. Is there a meaningful impact of this difference?

[jorgefilipecosta]

Hi @aduth,
In my tests, there is no difference between returning a null or empty string. In legacy widgets description is only used in the inspector, and empty string and null are both unrendered in React.

gutenberg/packages/block-library/src/legacy-widget/edit.js

Lines 95 to 97 in b421fc9

	<PanelBody title={ widgetObject.name }>
	{ widgetObject.description }
	</PanelBody>