Copying a table to the clipboard misses linebreaks for the "text/plain" flavor

[mbrodesser]

What is the current behavior? Describe the bug

1. Select the table from the example editor with the mouse.
2. Tap Ctrl+c to copy it to the clipboard.
3. Paste it to some text editor (or manually inspect the clipboard's "text/html" flavor).

What is the expected behavior?
The clipboard should contain linebreaks between all table rows.

Which versions of TinyMCE, and which browser / OS are affected by this issue? Did this work in previous versions of TinyMCE?
Affected version: 5.4.2-90.
Worked previously with version: 4.6.5.
Browser: current Firefox Nightly.
OS: Ubuntu 18.04.

See https://bugzilla.mozilla.org/show_bug.cgi?id=1646457 for more context.

[lnewson]

Thanks for the report @mbrodesser! I can confirm this is a bug within the table plugin. This appears to be happening because TinyMCE is calling innerText on a detached table element, which causes the browser to not include the new lines and relevant spaces.

Anyways, I've logged an internal task for us to investigate this more. We'll update this issue when more information becomes available.