get_block_wrapper_attributes() function strips falsy values like zero

[wildworks]

discovered while working on the Gutenberg project: ​https://github.com/WordPress/gutenberg/pull/74183#discussion_r2645807647

A zero value is a valid value for the id, class and aria-label attributes, but because the empty function is used, the value is unintentionally removed.

Steps to reproduce

• Crate a new post.
• Insert an Archive block.
• Open the Advanced panel and enter 0 as the Additional CSS Class.
• This will appear in the code editor: <!-- wp:archives {"className":"0"} /-->
• On the front end, open your browser developer tools and you'll see that the class attribute is missing from that block.

Trac ticket: https://core.trac.wordpress.org/ticket/64452

[wildworks]

To achieve the ideal fix, the scope is a little larger than originally planned, but ​PR 10663 does the following:

• Move the get_block_wrapper_attirbutes() function from wp-includes/class-wp-block-supports.php to wp-includes/blocks.php because it is unnatural for the function to be in a class file.
• I noticed that there are no unit tests for the get_block_wrapper_attirbutes() function itself. This time, I only tested the zero value, but maybe we should test attribute merging in the future.
• Not only the get_block_wrapper_attirbutes() function but also apply_block_support() method was corrected.

Thanks both for your reviews!

I thought it was odd to have the get_block_wrapper_attributes function in a class file, so I moved it to block.php, but it became harder to see what had changed 😅 For now, I'll revert the function to its original position.

Thanks to both of you for the reviews! Before making any changes to this PR, I'd like to double-check what values ​​should be allowed for the attribute.

My understanding is as follows, but what do you think?

• ✅ Allow as valid value:
  • "0" (String)
  • 0 (Integer) → Should be converted to a string "0"
• ❌ Don't allow as invalid value
  • true (boolean)
  • false (boolean)
  • null
  • array() (array)

Trac ticket: https://core.trac.wordpress.org/ticket/64452

Oh, I re-forked the wordpress-develop repo and it seems all my submitted open PRs were closed 😂 I submitted a new PR that is equivalent to this one. ​https://github.com/WordPress/wordpress-develop/pull/10921