Pasting unformatted text removes formatting and converts heading to paragraph

[oxyc]

Describe the bug

If I paste an unformatted word (eg. copied from the URL bar) into an empty heading block or a paragraph with styling applied, all styling is reset and the block is converted to a paragraph.

To reproduce

1. Create a Heading block
2. Copy an unformatted word, eg a word from the URL bar of the browser
3. Paste it into the block
4. Notice that the block is now a paragraph.

Same happens if you paste it into the styled placeholder paragraph block in Media & Text.

Expected behavior

If I paste an unformatted word I would expect it to keep the previous styling and block type rather than resetting everything to an unformatted paragraph.

Desktop (please complete the following information):

• OS: macOS
• Browser Chrome
• Version 76

Additional context

This works as expected with v4.7.1 and v5.5.0. It does not work in v5.9.1, v6.2.0 and master branch.

[nerrad]

I'm able to reproduce in the editor included with WordPress 5.2.2 but not with Gutenberg active and built from the latest master branch. @oxyc can you try again using the latest master branch?

[oxyc]

Still happening with the playground on master branch for me. I can confirm it with the plugin tomorrow soon.

[nerrad]

To clarify, I'm not testing using the playground against Master but am using the build from master tested in a WordPress install. There may be a variation between GB in playground and in a WP environment that may be contributing to this then.

[oxyc]

This also happens with the plugin for me. Tested in Safari, Chrome and Firefox, all of them behave the same.

I ran these steps to build the plugin:

git pull origin master
npm run package-plugin
mv gutenberg.zip ~/......

[oxyc]

Just saw there's apparently https://wordpress.github.io/gutenberg/ which is built on master according to #16967 (comment).

It's reproducible there too.

[peterwilsoncc]

I've tested this locally and am having a similar problem, please find a screencast attached.

Testing environment

• WordPress 5.2.2
• Gutenberg master@ 0b4d9c8
• Chrome 76.0/macOS 10.13.6

Build environment

• node 10.16.0
• npm 6.9.0
• built with npm run build, ie not running in dev mode

Console output

Received HTML:

 
index.js?ver=1566448714:12 Received plain text:

 Pens and pencils
index.js?ver=1566448714:2 Processed HTML piece:

 <p>Pens and pencils</p>
index.js?ver=1566448714:12 Received HTML:

 
index.js?ver=1566448714:12 Received plain text:

 Pens and pencils
index.js?ver=1566448714:2 Processed HTML piece:

 <p>Pens and pencils</p>

[ellatrix]

The problem is that we always force BLOCKS mode in the paste handler when the input field is empty. I remember there being a reason for it, but I forgot, and unfortunately it's not commented on. I'll search through some similar issues for an answer.

Regardless, whatever it did fix, we should find something better, because enforcing BLOCKS mode for an empty block seems like the wrong approach.

[ellatrix]

Related: #10614, #6516, but not seeing the answer there.

[ellatrix]

Found it. This code was added 2 years ago to tigger embedding when pasting a URL on an empty line. #3326

I'll work on a fix now.

[ellatrix]

This issue is also a blocker for me to introduce splitting to captions. Without a fix you wouldn't be able to paste in an empty caption.