List: Add border support

[aaronrobertshaw]

Part of: #43241

What?

Adopts border support for the List block

Why?

• Offers greater design flexibility
• Improves consistency in design tooling with other blocks

How?

• Adopts all the available border block supports
• Makes the border controls optional to match the dimension controls
• Defines a custom selector so global styles only target top-level List blocks

Testing Instructions

• In the site editor, add a List block with some items including a nested list or two, to a page
• Style List blocks via Global Styles and confirm the editor and frontend display correctly
• Override the global styles on the block instance and confirm they display appropriately in the editor and frontend
• Confirm block instance styles apply correctly to nested List blocks

Screenshots or screencast

Screen.Recording.2024-08-09.at.7.57.40.PM.mp4

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Co-authored-by: aaronrobertshaw <aaronrobertshaw@git.wordpress.org>
Co-authored-by: andrewserong <andrewserong@git.wordpress.org>
Co-authored-by: carolinan <poena@git.wordpress.org>

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[andrewserong]

Overall this is testing well for me and according to the PR description 👍

Something I noticed while adding styles in global styles is that nested list items use a List block themselves, so setting a List block to have a border in global styles also means it'll apply to children:

In sites that do that, it's still possible to override the child list block by setting it to explicitly have a 0 width border:

For the use case of this sort of border — i.e. a theme that wishes to set a border on the outer list but not apply to the inner list items, would that be a good use case for someone to add a block style variation instead? If so, I imagine this PR will enable that, too. In any case, these are just thoughts off the top of my head while playing around with this... I don't think it's a blocker for this PR.

LGTM! 🚀

[aaronrobertshaw]

Thanks for the review @andrewserong 🚀

As there is no hurry on landing this, I'll find some time to try updating the selector for the border support to see if it can be made to target the parent list block only. If possible, we can then choose which feels the most natural.

[carolinan]

When adding the wp-block list class to the block, I brought this up, that the same class would be used for the nested lists, and that it would not be possible to style only the parent. But there was no support for adding separate classes or a second class to the nested item.

[aaronrobertshaw]

Thanks for the extra context @carolinan 👍

Leveraging the Selectors API, it's pretty trivial to make the Global Styles target only top-level List blocks. In 2fa7e3a I added a selector for the border styles that uses :not(.wp-block-list .wp-block-list) to prevent matching on nested lists.

It would be possible to give other features (e.g. spacing) the same treatment but spacing, typography, etc. do seem more "global" than say borders.

The video below shows me fumbling around the first time I tested out the latest changes. I think it does the job. The global style only adds the border to the outer List. The block instance styles can still override the values of global styles and also be used to add borders to inner blocks if so desired.

Screen.Recording.2024-08-09.at.7.57.40.PM.mp4

would that be a good use case for someone to add a block style variation instead?

Whichever way we go a block style variation could be created to achieve the desired result.

If we choose to only apply global styles to the outer List block, then a block style variation for Lists could define a border on inner List block types. The result being borders on all lists.

If we go with the original approach in this PR, the block style variation would just define border style none or border width 0 etc on inner List blocks.

Let me know what you think of the current behaviour. I'm probably leaning towards landing that approach.

[andrewserong]

Let me know what you think of the current behaviour. I'm probably leaning towards landing that approach.

Similar to the work over in #63541, I agree, and in testing this is working nicely for me, with the border applied to the outer most list:

I tested the following:

✅ Setting borders for the list in global styles applies only to the outer-most list, and not nested lists
✅ Overriding at the individual block level works as expected
✅ Individual lists and nested lists can still use block-level styles for borders
✅ Tested in the site editor, site frontend, and post editors

LGTM! 🚀

[carolinan]

Perfect, thank you