ECA Form breaks complex IEF widget

The error is caused by \Drupal\eca_form\HookHandler::inlineEntityFormAfterBuild. When I disable that callback by inserting a return $form; into the first line of it, the error disappears.

The problem is that IEF is not creating the correct embedded entity, at the same time there are no error messages or exceptions whatsoever.

Also, selecting an existing entity in such complex IEFs doesn't work either. See also 🐛 Nested IEF (complex form) stopped working for inner form Active .

A matter of fact, IEFs with the simple widget are not affected.

I'll start with an MR to disable the hook handler for complex IEFs so that people can use that patch until we've found a proper solution for this.

Turn out, when we revert the "bugfix" from 🐛 An error occurred while trying to build an inline entity from submitted form values Fixed then the issue disappears as well.

I've now disabled that code block from the other bug fix, but only for complex IEF widgets. This is just a workaround, but that can be applied to avoid that issue for now.

I have now disabled that complex widget hook entirely until we get a solution for this.

Turns out, disabling complex widgets entirely breaks some existing models, that otherwise with the workaround from the MR would be OK.

So, we're now merging and back porting the MR, publish another bug fix release and then hope that we can still find a proper solution for the underlying problem. But at least we would not be breaking anything in the meantime.