Added caution block under delete_empty to warn the developer when he try to activate delete_empty

for collections of compound forms.

Author: murilolobato

reference/forms/types/collection.rst

@@ -268,6 +268,13 @@ delete_empty
 
 **type**: ``Boolean`` **default**: ``false``
 
+.. caution::
+
+    Delete empty will only remove items when the normalized value is null.
+    If your `type`_ is a compound form type, you need to have the :ref:`required <reference-form-option-required>`
+    option set to ``false`` inside `options`_, See :ref:`empty_data <reference-form-option-empty-data>`.
+
+
 If you want to explicitly remove entirely empty collection entries from your
 form you have to set this option to true. However, existing collection entries
 will only be deleted if you have the allow_delete_ option enabled. Otherwise

reference/forms/types/form.rst

@@ -80,6 +80,8 @@ option on the form.
 
 .. include:: /reference/forms/types/options/data_class.rst.inc
 
+.. _reference-form-option-empty-data:
+
 .. include:: /reference/forms/types/options/empty_data.rst.inc
     :end-before: DEFAULT_PLACEHOLDER