Pasting valid Gutenberg block markup throws a "unexpected or invalid mark-up" error

[dsas]

Describe the bug:

I should be able to paste some valid Gutenberg block-markup into the editor without it erroring.

To reproduce:

1. Install co-blocks (can't reproduce without)
2. Open the post editor
3. Paste the following, completely valid mark-up (or insert a pattern with the same):

<!-- wp:heading {"className":"has-custom-font","fontFamily":"dm-sans"} -->
<h2 class="wp-block-heading has-custom-font has-dm-sans-font-family">Summer<br>Vibe</h2>
<!-- /wp:heading -->

5. See "This block contains unexpected or invalid content." message

The problem isn't limited to heading blocks, the same happens for paragraphs too (and probably more).

Expected behavior:

I expected a Heading block to be inserted without any mention of unexpected errors.

Screenshots:

Console output says:

Block validation: Block validation failed for `core/heading` ( 
Object { name: "core/heading", icon: {…}, keywords: (2) […], attributes: {…}, providesContext: {}, usesContext: [], supports: {…}, styles: [], variations: [], save: heading_save_save(_ref)
, … }
 ).

Content generated by `save` function:

<h2 class="wp-block-heading has-dm-sans-font-family has-custom-font" style="font-family:dm-sans">Summer<br>Vibe</h2>

Content retrieved from post body:

<h2 class="wp-block-heading has-custom-font has-dm-sans-font-family">Summer<br>Vibe</h2>

I think applyStyle is taking the fontFamily block attribute and putting it into the style prop, even though that's not necessary in Core.

Isolating the problem:

• This bug happens with no other plugins activated
• This bug happens with a default WordPress theme active (can repro with TT3 and non-default themes)
• This bug happens without the Gutenberg plugin active (can also repro with gutenberg trunk)
• I can reproduce this bug consistently using the steps above

WordPress version:

6.2

Gutenberg version:

Either trunk at the time of writing, GB1.15 or whatever WP6.2 ships.

[olafleur-godaddy]

Thanks for the report!

[olafleur-godaddy]

Reproduced in CoBlocks 2.25.5 with WP 6.1.1