contract/product_contract/views/product_template_view.xml

<?xml version="1.0" encoding="utf-8"?>

<!--
    Copyright 2017 LasLabs Inc.
    License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
-->

<odoo>

    <record id="product_template_form_contract_view" model="ir.ui.view">
        <field name="name">account.invoice.select.contract</field>
        <field name="model">product.template</field>
        <field name="inherit_id" ref="product.product_template_form_view"/>
        <field name="arch" type="xml">
            <xpath expr="//div[@name='options']" position="inside">
                <div>
                    <field name="is_contract" />
                    <label for="is_contract" />
                </div>
            </xpath>
            <xpath expr="//group[@name='group_standard_price']" position="inside">
                <field name="contract_template_id"
                       attrs="{'invisible': [('is_contract', '=', False)],
                               'required':[('is_contract', '=', True)]}" />
            </xpath>
        </field>
    </record>

</odoo>