Undefined array key in widgets.php on line 919

[sageth]

If you enable a plugin with a widget and then go to a page which does not display the widget (e.g. a Jetpack sitemap), you will receive an error similar to:
PHP message: PHP Warning: Undefined array key "jetpack-search-filters-1" in /wp-includes/widgets.php on line 918
PHP message: PHP Warning: Trying to access array offset on value of type null in /wp-includes/widgets.php on line 918" while reading response header from upstream, ...,
request: "GET /attachment-sitemap4.xml HTTP/2.0", ...,
referrer: "/sitemap_index.xml"

The issue appears to occur with some plugins, but not all and adding a check to see if the variable is set first seems to address the issue. There is no identified front-end impact, however, this can quickly fill up logs depending on your site traffic and configuration.

Testing can be completed by using Jetpack Search and Rank Math Sitemap xml files, though other combinations exist.

In some cases, viewing a page or post will cause a PHP warning:

PHP Warning: Trying to access array offset on value of type null in /wp-includes/widgets.php on line 918" while reading response header from upstream, ...,
request: "GET /attachment-sitemap4.xml HTTP/2.0", ...,
referrer: "/sitemap_index.xml"

This appears to be a logging issue only.

Description of Change: Adding a check to see if the widget ID is set prior to evaluation.

Trac ticket: https://core.trac.wordpress.org/ticket/57518

[Ipstenu]

I'm seeing this with Jetpack and (I think...) YoastSEO as well.

It would be nice to have this in core since it's a fairly minor change and (having tested) does work.

@Sageth are you still around and able to bring this up to date with trunk?

@Sageth are you still around and able to bring this up to date with trunk?

Updated with trunk as well as adding parenthesis suggestion and addressing the code standard failure.

https://core.trac.wordpress.org/ticket/57518

This includes a test for this condition.

[josephscott]

I have a version of this that includes a test for the condition that generates the warning - ​https://github.com/WordPress/wordpress-develop/pull/10710

There's one error:

1) Tests_Widgets_WpBlockThemeRegisterClassicSidebars::test_should_reregister_previous_theme_sidebar
PHPUnit\Framework\InvalidArgumentException: Argument #1 of PHPUnit\Framework\Assert::assertArrayNotHasKey() must be an integer or string

/var/www/tests/phpunit/tests/widgets/wpBlockThemeRegisterClassicSidebar.php:54
phpvfscomposer:///var/www/vendor/phpunit/phpunit/phpunit:106
/var/www/vendor/bin/phpunit:118

Thank you - I should have ran a broader set of the tests before pushing this. Updated.

[westonruter]

In 61466:

Widgets: Ensure a widget is registered prior to checking its ID in is_active_widget().

This avoids a possible PHP warning due to an undefined array key.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/10710

Follow-up to [11090], [7080].

Props sageth, josephscott, Ipstenu, mindctrl, westonruter.
See #8441, #6023.
Fixes #57518.