PHP 8.5: Interactivity API: Cannot use bool as array

[swissspidy]

Parent ticket for all things PHP 8.5: #63061

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Here's the error output when running unit tests against PHP 8.5:

4) Tests_Interactivity_API_WpInteractivityAPI::test_process_directives_doesnt_change_html_if_contains_unbalanced_tags with data set "DIV closer after" ('<div data-wp-bind--id="myPlug...</div>')
Cannot use bool as array

/var/www/src/wp-includes/interactivity-api/class-wp-interactivity-api.php:426
/var/www/src/wp-includes/interactivity-api/class-wp-interactivity-api.php:370
/var/www/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php:823
/var/www/vendor/bin/phpunit:122

5) Tests_Interactivity_API_WpInteractivityAPI::test_process_directives_doesnt_change_html_if_contains_unbalanced_tags with data set "DIV closer before" ('</div><div data-wp-bind--id="...</div>')
Cannot use bool as array

/var/www/src/wp-includes/interactivity-api/class-wp-interactivity-api.php:426
/var/www/src/wp-includes/interactivity-api/class-wp-interactivity-api.php:370
/var/www/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php:823
/var/www/vendor/bin/phpunit:122

6) Tests_Interactivity_API_WpInteractivityAPI::test_process_directives_doesnt_change_html_if_contains_unbalanced_tags with data set "DIV closer inside" ('<div data-wp-bind--id="myPlug...</div>')
Cannot use bool as array

/var/www/src/wp-includes/interactivity-api/class-wp-interactivity-api.php:426
/var/www/src/wp-includes/interactivity-api/class-wp-interactivity-api.php:370
/var/www/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php:823
/var/www/vendor/bin/phpunit:122

7) Tests_Interactivity_API_WpInteractivityAPI::test_process_directives_doesnt_change_html_if_contains_unbalanced_tags with data set "SPAN closer after" ('<div data-wp-bind--id="myPlug.../span>')
Cannot use bool as array

/var/www/src/wp-includes/interactivity-api/class-wp-interactivity-api.php:426
/var/www/src/wp-includes/interactivity-api/class-wp-interactivity-api.php:370
/var/www/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php:823
/var/www/vendor/bin/phpunit:122

The issue is the list( $opening_tag_name, $directives_prefixes ) = end( $tag_stack ); line when $tag_stack is empty. end() returns false for empty arrays, but list() expects an array.

Can't use list on false or empty array.

This implicitly worked, but doesn't anymore on PHP 8.5

Trac ticket: https://core.trac.wordpress.org/ticket/63977

[swissspidy]

In 60741:

Interactivity API: Fix "Cannot use bool as array" error.

Improves PHP 8.5 compatibility where calling list() on an empty array throws a warning.

Props swissspidy, jonsurrell, mukesh27.
Fixes #63977.
See #63061.