<xpath expr="//field[@name='partner_id']" position="replace">
<field name="partner_id" on_change="onchange_partner_id(partner_id, context)" context="{'search_default_customer':1}" attrs="{'readonly': [('state','in', ('paid', 'done', 'invoiced'))]}" required="1" />
</xpath>
<xpath expr="//field[@name='partner_id']" position="replace">
<field name="partner_id" on_change="onchange_partner_id(partner_id, context)" context="{'search_default_customer':1}" attrs="{'readonly': [('state','in', ('paid', 'done', 'invoiced'))]}" required="1" />
</xpath>