Gutenberg wp-block-code adds <br> tags for empty lines within <pre><code>

[Digiover]

Description

When adding a code snippet using the code block,
HTML tags are added to the source instead of respecting EOL (end of line) like CRLF/CR.

Step-by-step reproduction instructions

1. Go to Dashboard > Posts > Add New Post
2. Choose the code block
3. Write code...
4. See the result after publishing or preview

Screenshots, screen recording, code snippet

The result HTML code is (when using "Copy Element" in Chrome DevTools):

<pre class="wp-block-code"><code>PS C:\Users\Jan&gt; Measure-Command { Test-NetConnection -ComputerName smtp.gmail.com -Port 25 }
<br>
<br>Days              : 0
<br>Hours             : 0
<br>Minutes           : 0
<br>Seconds           : 0
<br>Milliseconds      : 349
<br>Ticks             : 3498166
<br>TotalDays         : 4.04880324074074E-06
<br>TotalHours        : 9.71712777777778E-05
<br>TotalMinutes      : 0.00583027666666667
<br>TotalSeconds      : 0.3498166
<br>TotalMilliseconds : 349.8166</code></pre>

Environment info

WordPress 6.4.2
Gutenberg 17.2.0

Verified with multiple WordPress instances, different syntax highlighting plugins and without. Problem first noticed in Gutenberg version 16.9.0.

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[Digiover]

Addendum

What I meant with

Problem first noticed in Gutenberg version 16.9.0.

is that 16.9.0 was the first version I noticed markup issues with code blocks (EOL completely missing, everything came on line line). Now with 17.2.0 the <br>'s are added withing <pre><code>

[t-hamano]

Thanks for the report.

I was also able to confirm this symptom, but I think this behavior is an intentional change.

The PR related to this change is #55999, which mentions:

Now all rich text values serialise the same way, with line breaks always serialising to the HTML BR tag.

I don't think this behavior is a bug, so I'd like to close this issue, but if there's anything I've missed, please comment.

[Digiover]

Thank you for your reply @t-hamano . Can't say I'm happy with it though...

Apparently, it's allowed to use <br> in <pre> according to the HTML specifications (https://developer.mozilla.org/en-US/docs/Web/HTML/Element/pre#technical_summary, https://developer.mozilla.org/en-US/docs/Web/HTML/Content_categories#phrasing_content) but it's changes like these that break sites. Since Gutenberg 16.9.0 -for as far as I remember- my site's code blocks are all messed up, without any indication why.

And now I still have to edit every post to fix code blocks, because I guess this isn't getting reversed.

[t-hamano]

@digover

Is the code block you're using from Gutenberg core? If so, I think this should be fixed on Gutenberg's side.

[Digiover]

@digover

Is the code block you're using from Gutenberg core? If so, I think this should be fixed on Gutenberg's side.

Yes, it's the Gutenberg core code block. But I have had "syntax highlighting" plugins installed, so there is no telling what is in my database now :) I removed those plugins a while ago.

Just tested it quickly: I do have to edit a code block. First image is how a random posts code block looks, second image is after editing (I added EOL's until </filter>, but pressing Update fixed the entire block. Caveats:

1. Other blocks remain unchanged (image 3)
2. only opening the "edit post" page en pressing "Update" doesn't do anything to fix the block. I have to change the block. See image 4, which is image 3 after inserting an space.

/edit: fixed image order

[t-hamano]

@Digiover

Sorry it took so long to reply. I haven't yet had enough time to look into this issue in detail, but I'm wondering if it's an issue with the code block itself, or with a compatibility issue with the plugin extending the code block. I would like to keep this issue open until there is clarity.

[t-hamano]

I would like to add this issue to the WP6.5 project board as it might affect many developers.

[Digiover]

Yeah great, @t-hamano . Anything I can do to help / assist? I've been out of the WP dev business quite some time but can always test or something.

[t-hamano]

Sorry for getting in touch with you so late. It turns out that the problem you reported has a much larger impact than I expected. A summary of the problem is summarized in #58659.

[t-hamano]

I think #58659 covers this issue, so I'd like to close it.