Issue with replacement for filter deprecation

[renathoc]

The function apply_filters_deprecated has the default value for the $replacement argument as false.

This function uses the _deprecated_hook, sending the same $replacement argument. But in the _deprecated_hook, it considers the default as null.

So the problem occurs when we use the apply_filters_deprecated without a replacement, the with no alternative available message is not shown, but Use instead.

[SergeyBiryukov]

Hi there, welcome to WordPress Trac! Thanks for the ticket.

The issue is already fixed for WordPress 5.4 in [46792] / #48817.

That said, I think we should switch the default values for $replacement and $message parameters in these functions to an empty string instead of null, to match the documented type of string. The ! is_null() check for these parameters seems unnecessarily strict, we only need to check for a truthy value.

This would affect:

• _deprecated_function()
• _deprecated_constructor()
• _deprecated_file()
• _deprecated_argument()
• _deprecated_hook()
• apply_filters_deprecated()
• do_action_deprecated()

[renathoc]

Great! Thank you @SergeyBiryukov

[jignesh.nakrani]

changed default values for $replacement and $message parameters to string and fixed ! is_null() strict type check

[SergeyBiryukov]

In 48327:

Plugins: Consistently use an empty string as the default value for $replacement and $message parameters in:

• _deprecated_function()
• _deprecated_constructor()
• _deprecated_file()
• _deprecated_argument()
• _deprecated_hook()
• apply_filters_deprecated()
• do_action_deprecated()

This matches the documented type of string for these parameters and removes unnecessarily strict ! is_null() checks.

Follow-up to [46792].

Props jignesh.nakrani, renathoc, SergeyBiryukov.
Fixes #49698.

[jrf]

Just came across this patch and noticed that the changes in the default value did not get a @since changelog entry while they do need one to inform plugin/themes which use these functions.