Hello, 

Currently in Odoo warning on the onchange product is available for the only sale.order  (Sale module). It is not raised when you change the product in account.invoice.  Generally in Odoo invoice is created from sale.order so they are not put this option in invoicing. 

So to raise a warning on adding a product to an invoice you have to call the onchange method of product in account.invoice and raise warning.

you can refer the below method in sale module sale.py : 1002:

@api.multi

    @api.onchange('product_id')

    def product_id_change(self):

        if not self.product_id:

            return {'domain': {'product_uom': []}}

        vals = {}

        domain = {'product_uom': [('category_id', '=', self.product_id.uom_id.category_id.id)]}

        if not self.product_uom or (self.product_id.uom_id.id != self.product_uom.id):

            vals['product_uom'] = self.product_id.uom_id

            vals['product_uom_qty'] = 1.0

        product = self.product_id.with_context(

            lang=self.order_id.partner_id.lang,

            partner=self.order_id.partner_id.id,

            quantity=vals.get('product_uom_qty') or self.product_uom_qty,

            date=self.order_id.date_order,

            pricelist=self.order_id.pricelist_id.id,

            uom=self.product_uom.id

        )

        result = {'domain': domain}

        title = False

        message = False

        warning = {}

        if product.sale_line_warn != 'no-message':

            title = _("Warning for %s") % product.name

            message = product.sale_line_warn_msg

            warning['title'] = title

            warning['message'] = message

            result = {'warning': warning}

            if product.sale_line_warn == 'block':

                self.product_id = False

                return result

        name = product.name_get()[0][1]

        if product.description_sale:

            name += '\n' + product.description_sale

        vals['name'] = name

        self._compute_tax_id()

        if self.order_id.pricelist_id and self.order_id.partner_id:

            vals['price_unit'] = self.env['account.tax']._fix_tax_included_price_company(self._get_display_price(product), product.taxes_id, self.tax_id, self.company_id)

        self.update(vals)

        return result

If you want more help you can contact us.

Thank You.

Hi,

It seems you are looking for something  in invocing like raise a warning if the selected product is out of stock. As you know by default this is there in the sale order but the same is not there in the invoice.

In the invoicing the product is not a required field. If you need the same functionality of the sale in invoicing, you can copy the onchange function in the sale which raise the warning to invoicing.

Thanks