Delete non line type before unlink invoice lines

issue3001

invoice.py

@@ -49,6 +49,6 @@ class InvoiceLine:
     def delete(cls, lines):
         PurchaseLine = Pool().get('purchase.line')
         if any(l for l in lines
-                if isinstance(l.origin, PurchaseLine)):
+                if isinstance(l.origin, PurchaseLine) and l.type == 'line'):
             cls.raise_user_error('delete_purchase_invoice_line')
         super(InvoiceLine, cls).delete(lines)

purchase.py

@@ -36,15 +36,18 @@ class Purchase:
         invoice = super(Purchase, self).create_invoice(invoice_type)
 
         if invoice:
-            invoice_line_ids = [l.id for l in invoice.lines]
+            lines_to_delete = [l for l in invoice.lines if l.type != 'line']
+            lines = [l for l in invoice.lines if l.type == 'line']
+            invoice_line_ids = [l.id for l in lines]
             with Transaction().set_user(0, set_context=True):
-                InvoiceLine.write(invoice.lines, {
+                InvoiceLine.write(lines, {
                     'invoice': None,
                     'invoice_type': invoice.type,
                     'party': invoice.party.id,
                     'currency': invoice.currency.id,
                     'company': invoice.company.id,
                     })
+                InvoiceLine.delete(lines_to_delete)
             self.write([self], {
                 'invoices': [('unlink', [invoice.id])],
                 'invoice_lines': [('add', invoice_line_ids)],

tests/scenario_purchase_invoice_line_standalone.rst

@@ -179,6 +179,10 @@ Purchase 5 products::
     >>> purchase.lines.append(purchase_line)
     >>> purchase_line.product = product
     >>> purchase_line.quantity = 4.0
+    >>> purchase_line = PurchaseLine()
+    >>> purchase.lines.append(purchase_line)
+    >>> purchase_line.type = 'subtotal'
+    >>> purchase_line.description = 'Subtotal'
     >>> purchase.save()
     >>> Purchase.quote([purchase.id], current_config.context)
     >>> Purchase.confirm([purchase.id], current_config.context)