flectra/addons/account_asset/views/account_invoice_views.xml

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

    <!-- Add "Asset Category" to supplier invoices -->
    <record model="ir.ui.view" id="view_invoice_asset_category">
        <field name="name">account.invoice.supplier.form</field>
        <field name="model">account.invoice</field>
        <field name="inherit_id" ref="account.invoice_supplier_form"/>
        <field name="arch" type="xml">
            <xpath expr="//field[@name='invoice_line_ids']/tree/field[@name='account_id']" position="before">
                <field string="Asset Category" name="asset_category_id" domain="[('type','=','purchase')]" context="{'default_type':'purchase'}"/>
            </xpath>
            <xpath expr="//field[@name='partner_id']" position="after">
                <field name="asset_bool" invisible="1"/>
            </xpath>
            <xpath expr="//field[@name='partner_id']" position="attributes">
                <attribute name="attrs">{'readonly': [('asset_bool', '=', True)]}</attribute>
            </xpath>
            <xpath expr="//field[@name='invoice_line_ids']" position="inside">
                <field name="asset_bool" invisible="1"/>
            </xpath>
            <xpath expr="//field[@name='invoice_line_ids']" position="attributes">
                <attribute name="attrs">{'readonly': [('asset_bool', '=', True)]}</attribute>
            </xpath>
        </field>
    </record>

</flectra>