Possible to use role defined in rst_prolog as default_role?

[ipilcher]

I am using the rst_prolog setting to create an "arg" role, which I use for inline highlighting of function/method argument/parameter names.

rst_prolog = """
.. raw:: html

   <style type="text/css">
     .arg {
       font-family: monospace;
       font-size: 90%;
       font-weight: bold;
     }
   </style>

.. role:: arg
   :class: arg
"""

I would like to use this as the default role, so I that I can simply use single backticks (without the explicit role identifier) around argument names in my Python docstrings.

default_role = 'arg'

This doesn't work, though. I get the following warning.

WARNING: default role arg not found

Is there any way to make this work?

[AA-Turner]

Conceptually, all default_role does is apply the .. default-role:: directive to each document. Would the following work?:

rst_prolog = """
.. raw:: html

   <style type="text/css">
     .arg {
       font-family: monospace;
       font-size: 90%;
       font-weight: bold;
     }
   </style>

.. role:: arg
   :class: arg

.. default-role:: arg
"""

[ipilcher]

Seems to work. Thanks!