Block Library: Button: Remove title attribute handling

[aduth]

Previously: #17352, #19462 (comment), #19490 (comment), #616

This pull request seeks to remove UI controls which assign a title attribute for a block.

This is based on advisory resources and related core efforts which recommend that title attributes be avoided for links:

• https://html.spec.whatwg.org/multipage/dom.html#the-title-attribute
• https://silktide.com/blog/2013/i-thought-title-text-improved-accessibility-i-was-wrong
• https://developer.paciellogroup.com/blog/2012/01/html5-accessibility-chops-title-attribute-use-and-abuse/
• https://www.24a11y.com/2017/the-trials-and-tribulations-of-the-title-attribute/
• https://a11yproject.com/posts/title-attributes/
• https://core.trac.wordpress.org/ticket/24766

The proposed changes do not currently remove the attribute from the block definition, nor do they prevent the attribute from being applied when rendering the generating the block's saved markup. This is to avoid invalidations of existing blocks. We could potentially choose to implement a deprecation to remove the attribute altogether, but the implementation as proposed seemed simplest in that it merely prevents the addition of new titles.

Current Status: I'm considering this as blocked by the issue described in #19651 (comment), where an empty title would introduce a confusing user experience for editing links.

Testing Instructions:

Verify that when selecting a link for a Button block, the resulting post markup does not contain a title attribute:

1. Navigate to Posts > Add New
2. Insert a Buttons block
3. Assign a link to the button (either to an external URL, or a search result for a post within the site)
4. Change to Code Editor using the editor's top-right "More Options" menu
5. Verify that the resulting markup does not contain a title attribute

Follow-up Tasks: If these changes are considered acceptable, a similar effort should be undertaken to remove the assignment of title attribute for the navigation link block:

gutenberg/packages/block-library/src/navigation/index.php

Lines 187 to 189 in c8a1eef

	if ( isset( $block['attrs']['title'] ) ) {
	$html .= ' title="' . esc_attr( $block['attrs']['title'] ) . '"';
	}

The "Image" block also includes title assignment, but my understanding is that it is not quite as problematic for use in images (see also #11054).

[MarcoZehe]

I'm all for this and the follow-ups. The less title attributes, the better for keyboard, touch, and screen readers.

Out of curiosity: I saw that you remove a title attribute on a div element here. Did that actually ever do anything useful even for sighted people? :-)

[aduth]

Out of curiosity: I saw that you remove a title attribute on a div element here. Did that actually ever do anything useful even for sighted people? :-)

Practically speaking, it was applying the title attribute to one of the button's wrapping elements in the editor. It does seem to have at least have had the impact of showing a visual tooltip when hovering over the button with the cursor. It's debatable that this was actually very useful, outside of replicating how the button would behave when shown on the front of the site.

[aduth]

The UX for an absent link title has been improved in #19739, so I'll remove the "[Status] Blocked" label.

Thanks @MarcoZehe for your comments at #19735 (comment) . I'll remove "Needs Accessibility Feedback" label accordingly.

I might like to invite some feedback from one or more of @mtias @getdave or @jorgefilipecosta in case there might be some justification to consider that we've missed for keeping these attributes.

[jorgefilipecosta]

Provided that we are ok with removing title attribute from links on the "a" element on the frontend it looks good to me 👍
I think it may make sense to add a comment in save.js above the title attribute saying that right now the attribute is never set?

[aduth]

I think it may make sense to add a comment in save.js above the title attribute saying that right now the attribute is never set?

That's a good thought. I added a comment in d32c29d.

[aduth]

As a follow-up to this, I created #19990 to remove the title HTML attribute from the Navigation Link block links as well.

[aduth]

See related: #20198