Remove ability to set root entry as parent when saving entry

[notnek]

I saw several issues (and PRs) around this (#1948, #1666, #2647) through other UI bits, but nothing for using a parent field when updating an entry. Since that field is part of the publish form and isn't required, I thought in the controller made the most sense. If there's another preferred way to accomplish this, I can update.

This bit us with a client a few weeks ago, but thankfully the sorting tree UI has already been patched around this.

[jelleroorda]

Awesome. We actually ran into this as well yesterday on our production site. Luckily it was just the CP that was broken. Like you described it's still possible to set a root page as the parent when creating/updating an entry. An alternative solution could be to create a validation error instead of silently ignoring it.

[jasonvarga]

Sorry, I'm having trouble working out what situation this is fixing. Can you explain it a little more or record a video?

[notnek]

Sorry, I'm having trouble working out what situation this is fixing. Can you explain it a little more or record a video?

Sure @jasonvarga. Here's the situation in action. When you choose the root page as your parent when editing an entry, the structure gets updated so that your entry is a child of the root entry instead of just being moved to the root of the tree.

statamic-parent-bug.mov

[jasonvarga]

Ah yes that's painfully obvious now. I tried a bunch of combinations and somehow missed that one. Thanks!

[jasonvarga]

Thank you for the PR but this now breaks the parent field completely.
Even if you choose a non-root as the parent, the entry will be moved to the top level.

This is because Entry::find(..) gives you an Entry object, which doesn't have an isRoot(). So, it always gets set back to null. We need to find the "page" instead. You can see how I solved this in #3104

[notnek]

Thanks @jasonvarga!