Widget Visibility: Fix thrown PHP error under specific block conditions

[LiamSarsfield]

Fixes HOG-336: Block Scanner: PHP Fatal TypeError in Widget Visibility Conditions

Proposed changes:

• Normalize $instance['content'] to a string before calling has_blocks() in Jetpack_Widget_Conditions::filter_widget.
• Guard serialize_blocks() to only run on parsed block arrays (checks for blockName), and bail safely on unknown/empty array shapes.
• Avoids a PHP 8+ TypeError when has_blocks() is invoked with an array.

Jetpack product discussion

N/A

Does this pull request change what data or activity we track or use?

N/A

Testing instructions:

• Prereqs:

  • PHP 8.1+ recommended.
  • Jetpack active with this branch installed.
  • Enable logging in wp-config.php if not already:
    • define( 'WP_DEBUG', true );
    • define( 'WP_DEBUG_LOG', true );
    • define( 'WP_DEBUG_DISPLAY', false );
  • Tail wp-content/debug.log while testing.

• Manual verification:

  • Activate a classic theme that uses legacy widgets (e.g., Twenty Twenty or Twenty Twenty-One). This functionality does not apply to block-based themes.
  • Ensure the Widget Visibility module is active in Jetpack settings.
  • Navigate to Appearance > Widgets.
  • Add a block-based widget (e.g., “Latest Posts”) to a sidebar.
  • In the block controls → Advanced, set Widget Visibility to “Show if” → “Page” → “Front page”.
  • Visit:
    • Front page: widget is visible.
    • Another page/post: widget is hidden.
  • Confirm no errors in wp-content/debug.log.

• Simulate "array content" code paths using a temporary MU plugin:

  • Create wp-content/mu-plugins/test-widget-visibility-content-shapes.php, or use an existing 01-snippets.php:

<?php
add_filter(
	'widget_display_callback',
	function ( $instance, $widget, $args ) {
		static $originals = array();

		// Only run when requested.
		$force_parsed_blocks = isset( $_GET['force_arr_content'] );
		$force_nested        = isset( $_GET['force_nested_content'] );

		if ( ! ( $force_parsed_blocks || $force_nested ) ) {
			return $instance;
		}

		// Only act on Block Widget instances, which carry block content.
		if ( ! ( $widget instanceof \WP_Widget_Block ) ) {
			return $instance;
		}

		// Must have string content to start with, or nothing to do.
		if ( empty( $instance['content'] ) || ! is_string( $instance['content'] ) ) {
			return $instance;
		}

		$widget_id = isset( $args['widget_id'] ) ? $args['widget_id'] : null;
		if ( ! $widget_id ) {
			return $instance;
		}

		// Store original string to restore at priority 11.
		$originals[ $widget_id ] = $instance['content'];

		// Present array shapes to Jetpack at priority 10.
		if ( $force_parsed_blocks ) {
			$blocks = parse_blocks( $instance['content'] );
			if ( is_array( $blocks ) && ! empty( $blocks ) ) {
				$instance['content'] = $blocks;
			}
		} elseif ( $force_nested ) {
			$instance['content'] = array( 'content' => $instance['content'] );
		}

		// Register a restoration callback once to revert to the original string after Jetpack runs.
		static $restorer_added = false;
		if ( ! $restorer_added ) {
			add_filter(
				'widget_display_callback',
				function ( $inst, $w, $a ) use ( &$originals ) {
					$wid = isset( $a['widget_id'] ) ? $a['widget_id'] : null;
					if ( $wid && isset( $originals[ $wid ] ) ) {
						$inst['content'] = $originals[ $wid ];
						unset( $originals[ $wid ] );
					}
					return $inst;
				},
				11,
				3
			);
			$restorer_added = true;
		}

		return $instance;
	},
	9,
	3
);

• With your test widget in place:

  • Visit the front page with ?force_arr_content=1 → no errors; visibility rules respected.
  • Visit with ?force_nested_content=1 → no errors; visibility rules respected.
  • Visit with ?force_unknown_shape=1 → no errors; widget displays (safe fallback).

• Check wp-content/debug.log for any TypeErrors/notices; expect none.

• Unit tests:

  • Run, and verify all have passed.

jetpack docker phpunit jetpack -- --filter=Jetpack_Widget_Conditions_Test

Before / After:

• Before: has_blocks() could be called with an array, causing a fatal error on PHP 8+ under certain block conditions.
• After: content is normalized first; has_blocks() only receives strings; array shapes are handled safely or bailed out conservatively.

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Review, ...).
  
• ✅ Add a "[Type]" label (Bug, Enhancement, Janitorial, Task).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

Follow this PR Review Process:

1. Ensure all required checks appearing at the bottom of this PR are passing.
2. Make sure to test your changes on all platforms that it applies to. You're responsible for the quality of the code you ship.
3. You can use GitHub's Reviewers functionality to request a review.
4. When it's reviewed and merged, you will be pinged in Slack to deploy the changes to WordPress.com simple once the build is done.

If you have questions about anything, reach out in #jetpack-developers for guidance!

---

Jetpack plugin:

No scheduled milestone found for this plugin.

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the fix/widget-visibility/array-string-conversion-error-hog-336 branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack fix/widget-visibility/array-string-conversion-error-hog-336

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/jetpack/modules/widget-visibility/widget-conditions.php	59/625 (9.44%)	1.32%	0 💚

Full summary · PHP report · JS report

[tbradsha]

I didn't test, but the code looks like it should address the issue. Thanks!

[tbradsha]

You could invert this and return early, de-nesting the rest of the block.

[tbradsha]

Also, thanks for adding test coverage!