Error creating content with title "title"

[idgserpro]

BUG/PROBLEM REPORT (OR OTHER COMMON ISSUE)

What I did:

Click the button to add a page, fill in the Title field with "title" and click Save.

What I expect to happen:

I expected Plone to create the page or report a validation error

What actually happened:

The error occurred:

Traceback (innermost last):
  Module ZPublisher.Publish, line 138, in publish
  Module ZPublisher.mapply, line 77, in mapply
  Module ZPublisher.Publish, line 48, in call_object
  Module plone.z3cform.layout, line 63, in __call__
  Module plone.z3cform.layout, line 47, in update
  Module plone.dexterity.browser.add, line 134, in update
  Module plone.z3cform.fieldsets.extensible, line 65, in update
  Module plone.z3cform.patch, line 30, in GroupForm_update
  Module z3c.form.group, line 145, in update
  Module plone.app.z3cform.csrf, line 22, in execute
  Module z3c.form.action, line 98, in execute
  Module z3c.form.button, line 315, in __call__
  Module z3c.form.button, line 170, in __call__
  Module plone.dexterity.browser.add, line 109, in handleAdd
  Module z3c.form.form, line 265, in createAndAdd
  Module plone.dexterity.browser.add, line 84, in add
  Module plone.dexterity.utils, line 189, in addContentToContainer
  Module OFS.ObjectManager, line 325, in _setObject
  Module Products.CMFCore.Skinnable, line 213, in _checkId
  Module OFS.ObjectManager, line 116, in checkValidId
BadRequest: The id "title" is invalid - it is already in use.

In Plone 4, this error doesn't occur.

What version of Plone/ Addons I am using:

Plone 5.1.6

[pbauer]

On http://demo.plone.org (Plone 5.2) this does not happen.

[jone]

I can confirm the problem on Plone 5.1.5 (5115). I see the problem in at least two separate projects (both have a different set of addons installed). The problem occurs in tests as well as in reality (I'm using ftw.builder in the tests)

[idgserpro]

As in Plone 5.2 it works and we will no longer have release of Plone 5.1, I will close this issue