[IMP] sale: Make advance_payment_method field understandable for the ordinary mortals

addons/sale/wizard/sale_make_invoice_advance.py

@@ -31,8 +31,8 @@ class SaleAdvancePaymentInv(models.TransientModel):
             return False
 
     advance_payment_method = fields.Selection([
-        ('delivered', 'Ready to invoice'),
-        ('all', 'Ready to invoice (with refunds)'),
+        ('all', 'Invoiceable lines'),
+        ('delivered', 'Invoiceable lines (without refunds)'),
         ('percentage', 'Deposit (percentage)'),
         ('fixed', 'Deposit (fixed amount)')
         ], string='What do you want to invoice?', default=_get_advance_payment_method, required=True)

addons/sale/wizard/sale_make_invoice_advance.xml

@@ -25,6 +25,11 @@
                                 attrs="{'invisible': [('advance_payment_method', '!=', 'percentage')]}" class="oe_inline"/>
                         </div>
                     </group>
+                    <div attrs="{'invisible': [('advance_payment_method', '!=', 'delivered')]}">
+                        <span class="oe_grey">
+                        Note that if you select 'Invoiceable lines (without refunds)', you won't be able to create an invoice with a negative total amount.
+                        </span>
+                    </div>
                     <footer>
                         <button name="create_invoices" string="Create and View Invoices" type="object"
                             context="{'open_invoices': True}" class="btn-primary"/>