If required, all cells need not be full

Works for me.

Works great, thanks!

Rerolled so it applies cleanly to 8.x-2.x. No changes made.

I had a few issues with this:

1. $form_state->getTriggeringElement() often wasn't set when I saved a node (with a tablefield inside a paragraph), so the validateTablefield() function wasn't being run. I removed that conditional from inside formElement() and changed it to use $form_state->isSubmitted()) inside validateTablefield().
2. When the table was reorder-able, the weight element inside the row was being counted as a value, so an empty table was still being saved. So we check for that.
3. All sub-fields of the tablefield were being highlighted as the error. I pass the table sub-field to setError(), since that's what we're checking has values.

Please use an issue fork and merge request.

I created a fork as requested and tried to apply patch #9 but it failed to apply. So I went through it line by line and applied it as closely as possible with what was there.

It has been 5 years since I created this issue and I no longer have access to a codebase that is using it. So I will need to rely on others to test this out.

Re-rolled on 3.0.x. Review and tests by others needed.