.. include:: /Includes.rst.txt

==========================
TYPO3 Exception 1458745712
==========================

.. include:: /If-you-encounter-this-exception.rst.txt

Invalid flex form data structure
================================

::

   Invalid flex form data structure on field name "pi_flexform" with
   element "..." in section container "section": Nesting sections in
   container elements sections is not allowed.

Background
==========

Support for editing/creating nested flex form section containers has
been blocked in TYPO3 7.4.5 due to issues in data consistency and
component handling.

See `Core bug report #73125 <https://forge.typo3.org/issues/73125>`__.

Nested sections in Flux aka "Fluid Powered TYPO3"
=================================================

Nesting sections could be thought of as "repeaters" inside "repeaters",
such as for a FCE which contained a dynamic list of contacts with
another dynamic list of phone numbers inside. Blockage of nested
sections in TYPO3 Core means that Flux isn't able to support these data
structures any more if TYPO3 7.4.5 or higher is being used.

A request for a flag to circumvent the blockage when Flux is being used
has been made but was rejected (see `TYPO3 Core bug report #76281 on
Forge <https://forge.typo3.org/issues/76281>`__, "Change 47369 killed
features in flux").

Flux developers stated that it was only meant to abstract core's API for
flex forms, thus support for nested sections was only available because
it was in Core. No workarounds will be implemented by "Fluid Powered
TYPO3" (i.e. neither flux or fluidcontent) and the Core exception will
not be caught (see `flux issue 1139 on
GitHub <https://github.com/FluidTYPO3/flux/issues/1139>`__, "Nesting
sections in container elements sections is not allowed.").

Impact
------

Previously created FCEs with nested sections can still be read (and
rendered), disabled/enabled, copied and deleted, but no longer be fully
edited in backend until all nested sections have been removed from the
FCE's Configuration section. Attempting to enter the edit view for a FCE
with such a structure now generally fails with the above exception being
displayed. Previously entered nested data seems to survive saving in BE
even after the data structure has been modified, but the absence of a
clean-up of such invalid data cannot be guaranteed for all times.

Workarounds
-----------

Using nested FCEs (containers/grid) instead
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Most times it's possible to split affected FCEs into one or more
container FCEs to contain special FCEs only meant for use inside these
containers.

For example, if you had a structure such as:

-  FCE "Contacts"

   -  Section/object "Person"

      -  Field "Name" => "John Doe"
      -  Section/object "Number"

         -  Field "Type" => "Phone"
         -  Field "Number" => "12345"

      -  Section/object "Number"

         -  Field "Type" => "Fax"
         -  Field "Number" => "54321"

   -  Section/object "Person"

      -  ...

You could split it so that you get:

-  FCE "Contacts Container"

   -  Grid column "Contacts"

      -  FCE "Contact Person"

         -  Field "Name" => "John Doe"

            -  Section/object "Number"

               -  Field "Type" => "Phone"
               -  Field "Number" => "12345"

            -  Section/object "Number"

               -  Field "Type" => "Fax"
               -  Field "Number" => "54321"

      -  FCE "Contact Person"

         -  ...