reword the regex note (#75393)

Co-authored-by: Matt Martz <matt@sivel.net>
Co-authored-by: Brian Scholer <1260690+briantist@users.noreply.github.com>

docs/docsite/rst/reference_appendices/faq.rst

@@ -811,6 +811,31 @@ and backups, which most file based modules also support:
              path: "{{ updated['backup_file'] }}"
              state: absent
 
+.. _jinja2_faqs:
+
+Why does the ``regex_search`` filter return `None` instead of an empty string?
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+Until the jinja2 2.10 release, Jinja was only able to return strings, but Ansible needed Python objects in some cases. Ansible uses ``safe_eval`` and  only sends strings that look like certain types of Python objects through this function. With ``regex_search`` that does not find a match, the result (``None``) is converted to the string "None" which is not useful in non-native jinja2.
+
+The following example of a single templating action shows this behavior:
+
+.. code-block:: Jinja
+
+  {{ 'ansible' | regex_search('foobar') }}
+
+This example does not result in a Python ``None``, so Ansible historically converted it to "" (empty string).
+
+The native jinja2 functionality actually allows us to return full Python objects, that are always represented as Python objects everywhere, and as such the result of a single templating action with ``regex_search`` can result in the Python ``None``.
+
+.. note::
+
+  Native jinja2 functionality is not needed when ``regex_search`` is used as an intermediate result that is then compared to the jinja2 ``none`` test.
+
+  .. code-block:: Jinja
+
+     {{ 'ansible' | regex_search('foobar') is none }}
+
 
 .. _docs_contributions:
 

docs/docsite/rst/user_guide/playbooks_filters.rst

@@ -1826,16 +1826,20 @@ The ``regex_search`` filter returns an empty string if it cannot find a match:
     {{ 'ansible' | regex_search('foobar') }}
     # => ''
 
-Note that due to historic behavior and custom re-implementation of some of the Jinja internals in Ansible there is an exception to the behavior. When used in a Jinja expression (for example in conjunction with operators, other filters, and so on) the return value differs, in those situations the return value is ``none``. See the two examples below:
 
-.. code-block:: yaml+jinja
+.. note::
+
+
+  The ``regex_search`` filter returns ``None`` when used in a Jinja expression (for example in conjunction with operators, other filters, and so on). See the two examples below.
+
+  .. code-block:: Jinja
 
     {{ 'ansible' | regex_search('foobar') == '' }}
     # => False
-    {{ 'ansible' | regex_search('foobar') == none }}
+    {{ 'ansible' | regex_search('foobar') is none }}
     # => True
 
-When ``jinja2_native`` setting is enabled, the ``regex_search`` filter always returns ``none`` if it cannot find a match.
+  This is due to historic behavior and the custom re-implementation of some of the Jinja internals in Ansible. Enable the ``jinja2_native`` setting if you want the ``regex_search`` filter to always return ``None`` if it cannot find a match. See :ref:`jinja2_faqs` for details.
 
 To extract all occurrences of regex matches in a string, use the ``regex_findall`` filter: