GOLEM/golem_activity_registration_payment/views/golem_activity_views.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
Copyright 2018 Youssef El Ouahby <youssef@yaltik.com>
Copyright 2018 Fabien Bourgeois <fabien@yaltik.com>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
-->

<odoo>
  <data>
    <!-- Forms -->
    <record id="golem_activity_form_inherit_activity_registration_payment"
      model="ir.ui.view">
     <field name="name">Golem activity form adaptations</field>
     <field name="model">golem.activity</field>
     <field name="inherit_id" ref="golem_activity.golem_activity_form" />
     <field name="arch" type="xml">
      <field name="list_price" position="attributes">
        <attribute name="attrs">{'invisible': [('free_activity', '=', True)]}</attribute>
      </field>
      <field name="list_price" position="before">
        <field name='free_activity' />
      </field>
     </field>
   </record>

   <!-- Search -->
   <record id="golem_activity_search_inherit_activity_registration_payment"
  model="ir.ui.view">
     <field name="name">Golem Activity Search adaptations</field>
     <field name="model">golem.activity</field>
     <field name="inherit_id" ref="golem_activity.golem_activity_search" />
     <field name="arch" type="xml">
       <filter name="season_default" position="after">
         <filter name="free_activity" string="Free activity"
           domain="[('free_activity', '=', True)]" />
       </filter>
     </field>
    </record>
  </data>
</odoo>