WordPress strips multiple line breaks inside of <pre> tags

[Viper007Bond]

Write a post:

<pre>
This


is




a
test.
</pre>

You end up with this:

<pre>
This

is

a
test.
</pre>

Probably related to wpautop() I imagine.

(In [16394]) Remove invalid parent paragraph when pasting in the visual editor or switching visual to HTML and back, keep multiple empty lines in a <pre> tag, fixes #15095 fixes #15367

This isn't a TinyMCE issue, it's an output filter issue.

Replying to Viper007Bond:
The same was happening when switching editors, perhaps we can apply the changes from the JS version of wpautop to the php one.

No I mean this isn't an editor issue. If I write the above example in the HTML editor, it stays exactly like that. I save the post, still correct. When I view it on the front end however, the extra line breaks are stripped out.

Whoops, I need to learn to read. Yes, we need to apply the code to the PHP-based `wpautp()~ too.

I also need to learn to spell apparently...

Nah you can spell apparently fairly well it's the other words you should practice ;-)

Related: #18534

Modified wpautop in formatting.php

My approach was to preserve all content inside <pre> tags from most of the substitution that occurs on the rest of the text. As a result, the call to clean_pre() is no longer necessary.

Closed #19666 as a duplicate.

This problem still exists but the patch would not apply. Needs Refresh.

In addition to my last comment the problem still exist when switching between Visual and Text mode. If you paste the example in text mode and click publish then reload the page it remains as it should. It seems a similar fix is needed for the js.