pms/pms_contract/views/pms_service.xml

<odoo>

    <record id="view_pms_service_form" model="ir.ui.view">
        <field name="name">pms.service.form</field>
        <field name="model">pms.service</field>
        <field name="inherit_id" ref="pms_base.view_pms_service_form" />
        <field name="arch" type="xml">
            <field name="vendor_id" position="after">
                <field
                    name="contract_id"
                    domain="[('contract_type', '=', 'purchase')]"
                    context="{'default_partner_id': vendor_id, 'default_contract_type': 'purchase'}"
                />
            </field>
        </field>
    </record>

    <record id="view_pms_service_tree" model="ir.ui.view">
        <field name="name">pms.service.tree</field>
        <field name="model">pms.service</field>
        <field name="inherit_id" ref="pms_base.view_pms_service_tree" />
        <field name="arch" type="xml">
            <field name="vendor_id" position="after">
                <field name="contract_id" />
            </field>
        </field>
    </record>

</odoo>