I was investigating reports that the object replacement character could be added to a post slug, and noticed that we had two definitions of cleanForSlug, with diverging behavior.

I fixed this by updating the function in the url package to include fixes from #24710, and re-exporting the function in the editor package. I think we can probably deprecate the url utils in the editor package (in either a follow up or in this PR), but let me know if folks have opinions on this.

Note that this is client-side sanitization, so this will help prevent new bad entries. For posts/slugs with existing bad characters we'll need a separate patch for server sanitization.

cc @claudiulodro @Robertght would it be possible to see if this also helps with: #38637

Testing Instructions

In console:

wp.url.cleanForSlug('Καλημέρα Κόσμε');

returns 'καλημέρα-κόσμε' instead of an empty string.

wp.editor.cleanForSlug('Καλημέρα Κόσμε');

Has the same result, but also includes a deprecation warning.

• In the post editor, make sure permalinks are set to include the post title
• Create a new post and save a draft
• Try editing the permalink slug to include non-latin characters, and unicode characters like the object replacement characters
• On blur unexpected characters should be sanitized.