Multi-line Code blocks from WP 5.5 lose line breaks when GB active

[westonruter]

Given an Code block with the content:

<!-- wp:code -->
<pre class="wp-block-code"><code>if ( a === b ) {
    doSomething();
}</code></pre>
<!-- /wp:code -->

In WP 5.5 when Gutenberg is inactive, this is rendered in the editor as follows:

When activating Gutenberg, however, this gets rendered in the editor as:

This appears to be a regression introduced in v9.1 with allowing HTML editing and rich text in the Code block: #24689, since the block's content attribute changed from a text source to an html source. This is in spite of the fact that the code is still in a pre.

If I try recreating this Code block with Gutenberg active, then I get this saved content:

<!-- wp:code -->
<pre class="wp-block-code"><code>if ( a === b ) {<br>    doSomething();<br>}</code></pre>
<!-- /wp:code -->

Note that <br> tags are now needed to represent line breaks instead of newline characters.

Is there a block deprecation function missing here?

cc @ellatrix @mkaz

[getdave]

I can confirm this is happening on my personal site as well.

[joyously]

I was testing something else, but saw this reformatting happening in the Classic block as well, which I don't think was happening before.

[talldan]

#26347 seems to fix a similar issue with indentation.

[tellthemachines]

Closing as fixed by #26347.