Do not change line type when calling on_change_product

The wizard to modify header calls on_change_product on all lines but their
type must not change.

Closes #12633

modules/purchase/purchase.py

@@ -1420,18 +1420,20 @@ class Line(sequence_ordered(), ModelSQL, ModelView):
                     and self.product_supplier not in product_suppliers):
                 self.product_supplier = None
 
-        self.unit_price = self.compute_unit_price()
+            self.unit_price = self.compute_unit_price()
 
-        self.type = 'line'
         self.amount = self.on_change_with_amount()
 
     @fields.depends(
-        'product',
+        'type', 'product',
         methods=['on_change_with_company', '_get_tax_rule_pattern'])
     def compute_taxes(self, party):
         pool = Pool()
         AccountConfiguration = pool.get('account.configuration')
 
+        if self.type != 'line':
+            return []
+
         company = self.on_change_with_company()
         taxes = set()
         pattern = self._get_tax_rule_pattern()

modules/purchase/tests/scenario_purchase_modify_header.rst

@@ -80,6 +80,7 @@ Create a sale with a line::
     >>> purchase_line.product = product
     >>> purchase_line.quantity = 3
     >>> purchase_line.unit_price = Decimal('5.0000')
+    >>> purchase_line_comment = purchase.lines.new(type='comment')
     >>> purchase.save()
     >>> purchase.untaxed_amount, purchase.tax_amount, purchase.total_amount
     (Decimal('15.00'), Decimal('1.50'), Decimal('16.50'))

modules/sale/sale.py

@@ -1492,18 +1492,20 @@ class SaleLine(TaxableMixin, sequence_ordered(), ModelSQL, ModelView):
             if not self.unit or self.unit.category != category:
                 self.unit = self.product.sale_uom
 
-        self.unit_price = self.compute_unit_price()
+            self.unit_price = self.compute_unit_price()
 
-        self.type = 'line'
         self.amount = self.on_change_with_amount()
 
     @fields.depends(
-        'product',
+        'type', 'product',
         methods=['on_change_with_company', '_get_tax_rule_pattern'])
     def compute_taxes(self, party):
         pool = Pool()
         AccountConfiguration = pool.get('account.configuration')
 
+        if self.type != 'line':
+            return []
+
         company = self.on_change_with_company()
         taxes = set()
         pattern = self._get_tax_rule_pattern()

modules/sale/tests/scenario_sale_modify_header.rst

@@ -82,6 +82,7 @@ Create a sale with a line::
     >>> sale_line = sale.lines.new()
     >>> sale_line.product = product
     >>> sale_line.quantity = 3
+    >>> sale_line_comment = sale.lines.new(type='comment')
     >>> sale.save()
     >>> sale.untaxed_amount, sale.tax_amount, sale.total_amount
     (Decimal('30.00'), Decimal('3.00'), Decimal('33.00'))