I have this block in a deliveryslip qweb report. It shows the product description instead of the product id. This just works if the delivery isn't in state done.

                   <table class="table table-sm mt48" t-if="o.state!='done'">
                        <thead>
                            <tr>
                                <th><strong>Product</strong></th>
                                <th><strong>Quantity</strong></th>
                            </tr>
                        </thead>
                        <tbody>
                            <t t-set="lines" t-value="o.move_lines.filtered(lambda x: x.product_uom_qty)"/>
                            <tr t-foreach="lines" t-as="move">
                                <td>
                                    <span t-field="move.name"/>
                                    <p t-if="o.picking_type_code == 'outgoing'">
                                        <span t-field="move.product_id.sudo().description_pickingout"/>
                                    </p>
                                    <p t-if="o.picking_type_code == 'incoming'">
                                        <span t-field="move.product_id.sudo().description_pickingin"/>
                                    </p>
                                </td>
                                <td>
                                    <span t-field="move.product_uom_qty"/>
                                    <span t-field="move.product_uom"/>
                                </td>
                            </tr>
                        </tbody>
                    </table>

I want just to add the same function; show the product decription if the state is done. Here the code.

​<table class="table table-sm mt48" t-if="o.move_line_ids and o.state=='done'">
                        <t t-set="has_serial_number" t-value="o.move_line_ids.mapped('lot_id')"/>
                        <thead>
                            <tr>
                                <th><strong>Product</strong></th>
                                <th name="lot_serial" t-if="has_serial_number" groups="stock.group_lot_on_delivery_slip">
                                    Lot/Serial Number
                                </th>
                                <th class="text-center"><strong>Quantity</strong></th>
                            </tr>
                        </thead>
                        <tbody>
                          <tr t-foreach="o.move_line_ids" t-as="move_line">
                            <td>
                              <span t-field="move_line.product_id"/>
                              <p t-if="o.picking_type_code == 'outgoing'">
                                  <span t-field="move_line.product_id.sudo().description_pickingout"/>
                              </p>
                              <p t-if="o.picking_type_code == 'incoming'">
                                  <span t-field="move_line.product_id.sudo().description_pickingin"/>
                              </p>
                            </td>
                            <td t-if="has_serial_number and move_line.lot_name" groups="stock.group_lot_on_delivery_slip">
                                <span t-field="move_line.lot_name"/>
                            </td>
                            <td t-else="" groups="stock.group_lot_on_delivery_slip">
                                <span t-field="move_line.lot_id.name"/>
                            </td>
                            <td class="text-center">
                                <span t-field="move_line.qty_done"/>
                                <span t-field="move_line.product_uom_id"/>
                            </td>
                          </tr>
                        </tbody>
                    </table>

The QWEB format is de default one:  stock.report_delivery_document