Gutenberg: Spacer block (attribute pruning)

[gwwar]

See #27294

As the most used block ;) let's make sure that we can insert this and it's serialized appropriately in post content

Status

Awaiting fix in core
Awaiting fix in D19247-code

[dmsnell]

Tested in current wpcalypso environment and it seemed to work as expected. I addd, resized, deleted, and reloaded a page with the spacers.

[dmsnell]

After reloading the page I discovered the problem - it appears as though Gutenberg is pruning attributes from the block on save.

Invalid reloaded block
Note the missing aria attribute

<!-- wp:spacer {"height":242} -->
<div style="height:242px;" class="wp-block-spacer"></div>
<!-- /wp:spacer -->

Valid new block

<!-- wp:spacer {"height":63} -->
<div style="height:63px" aria-hidden="true" class="wp-block-spacer"></div>
<!-- /wp:spacer -->

Tested in a separate Gutenberg/WordPress environment and the save/load loop was fine without breaking. I tested with Gutenberg from master@{two weeks ago} as well and it was still fine so this appears to be happening on the dotcom side.

---

Confirmed that the database has the malformed content. Looking for some filter on save.

[mcsf]

This is likely very similar to core's issue of filtering a saving post's HTML when a user isn't admin (unfiltered_html capability). See:

• Cover image cannot be added without unfiltered_html capability WordPress/gutenberg#2539
• Add needed attributes to kses allowed tags for the Gallery block WordPress/gutenberg#9875
• Extend allowed attributes for non-admin users WordPress/gutenberg#9954

The main reasons for some input to be filtered:

• Using aria-* attributes.
• Using data-* attributes.
• Using certain inline styles, notably url(), based on this mask.

The proper fix is to be done in core WP (kses). A core ticket for CSS's url() has been opened, but further work in kses is needed in order to whitelist aria- and data- wildcards.

[vindl]

@dmsnell just a note that I'm seeing a similar issue with Audio block after uploading and saving (tested with business plan because audio uploads aren't included in free).

[dmsnell]

after the merge of D19247-code the spacer block is working