Post Terms: Fix fatal error when 'get_the_term_list' returns 'WP_Error'

[up1512001]

What?

update the core/post-term render_block_core_post_terms function to handle WP_Error and not throw a fatal error.

Why?

fixes #65832

How?

• store get_the_term_list as a separate variable and check if it's WP_Error then simply return false otherwise return actual output.

Testing Instructions

• Add the Terms List block to the post.
• make get_the_term_list to return WP_Error.
• on the front end, you will not see any fatal error.

Screenshots or screencast

Screen.Recording.2024-10-03.at.11.42.19.mov

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Co-authored-by: up1512001 <up1512001@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>
Co-authored-by: david-binda <davidbinda@git.wordpress.org>

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[Mamaduka]

Thanks for contributing, @up1512001!

Can you share a code snippet for get_the_term_list to return a WP_Error?

The issue mentions filtering the get_the_terms, in which case an error should be caught early, and code execution shouldn't reach get_the_term_list.

gutenberg/packages/block-library/src/post-terms/index.php

Lines 27 to 30 in 20f35dd

	$post_terms = get_the_terms( $block->context['postId'], $attributes['term'] );
	if ( is_wp_error( $post_terms ) || empty( $post_terms ) ) {
	return '';
	}

cc @david-binda

[david-binda]

@Mamaduka sorry for the confusion on my end. The thing is that the get_the_term_list can return a WP_Error even in case the get_the_terms does not.

It would be the case when the get_term_link called from the get_the_term_list would return an instance of WP_Error.

As I have mentioned in the related issue, checking the return value of the get_the_term_list is what WordPress also does.

In order to reproduce the issue I've noticed in production logs, we could filter the get_the_terms in following fashion:

add_filter( 'get_the_terms', function( $terms, $post_id, $taxonomy ) {
    if ( array_key_exists( 0, $terms ) ) {
        $terms[0] = null;
    }
    return $terms;
}, 10, 3 );

[Mamaduka]

Thanks for the additional details, @david-binda!

I can confirm that this fixes the bug ✅