editor removing pre tag

[joyously]

When in Text mode, I enter a <pre> tag, with text in it all spaced out.
Switch to Visual mode, and the pre tag is removed, and the text spacing is removed.
Switch back to Text mode, there is no pre tag or spacing.

I'm not sure when this changed. I only noticed it because I wanted to test editor styles and switched to Visual mode (I usually stay in Text mode all the time).
I got this in the trunk version, but also on a site that is using WP 4.7.6.

[joyously]

Here is how it looks in 4.7.6

[iseulde]

Looking at the GIF, the HTML seems to be invalid. The H2 tag cannot be inside of a PRE tag: ​https://html.spec.whatwg.org/multipage/grouping-content.html#the-pre-element.

[joyously]

Here it is again with the H2 outside the pre tag. It does much better. The pre tag is not removed, but some of the entity replacement changes the white space that is supposed to be preserved.

[joyously]

Replying to iseulde:

Looking at the GIF, the HTML seems to be invalid. The H2 tag cannot be inside of a PRE tag: ​https://html.spec.whatwg.org/multipage/grouping-content.html#the-pre-element.

Just because the HTML is invalid (although that HTML still displays correctly in the browser), is no reason to strip out the pre tag. Since the only way to get the pre tag in there is to switch to Text mode, and then switch back to Visual to see how it looks, the editor could easily mess up a user's hard work. Even if it gave an indication of the problem, that would be better than silently removing what the user chose to put.

As you can see in the second attachment, there is still a problem with how the pre tag is handled when the invalid tags are removed. The HTML entity replacement does not preserve the whitespace, which is the whole point of pre.

[hdalive]

Faced the same issue. The pre tag is getting removed when switched to visual mode.

But when I removed the Heading tag from pre tag there is no issue. 0_o

[hdalive]

When i add

<i class="fa fa-code"></i>

near a heading tag it gets removed as well. Magic !!!

[dbodnariuc]

I am also facing the same problem.
I use <pre> tag to tell WP I have some code and to not modify it.
When I switch to visual editor, the <pre> tag gets stripped and the code is modified.