Code Modernization: Correct default values in wp_handle_comment_submission().
This affects the following parameters subsequently passed to wp_new_comment():
comment_author
comment_author_email
comment_author_url
comment_content
The default values for these parameters were previously set to null, causing PHP 8.1 "null to non-nullable" deprecation notices when running sanitization filters on them via wp_filter_comment().
While the deprecation notices were temporarily silenced in the unit test suite, that caused an unexpected issue in a test for submitting a comment to a password protected post, where the $_COOKIE[ 'wp-postpass_' . COOKIEHASH ] value was no longer unset, as the test stopped any further execution once the deprecation notice was triggered.
Due to how WordPress handles password protected posts, once that value is set, it affects all posts protected with the same password, so this resulted in unintentionally affecting another test which happened to use the same password.
These values are all documented to be a string in various related filters, and core also expects them to be a string, so there is no reason for these defaults to be set to null. Setting them to an empty string instead resolves the issues.
This commit includes:
- Setting the defaults in
wp_handle_comment_submission() to an empty string.
- Adding a dedicated unit test to verify the type of these default values.
- Removing the deprecation notice silencing as no longer needed.
Follow-up to [34799], [34801], [51968].
Props jrf, desrosj, mukesh27, SergeyBiryukov.
Fixes #56712. See #56681, #55656.