[IMP] sell_only_by_packaging: support negative rounding when converting packaging qty

Author: duongtq

sell_only_by_packaging/README.rst

@@ -34,11 +34,15 @@ sale orders.
 The creation/update of sale order line will be blocked (by constraints) if the data on the
 sale.order.line does not fit with the configuration of the product's packagings.
 
-It's also possible to force the quantity to sell during creation/modification of the sale order line
+It's also possible to force the quantity to sell/return during creation/modification of the sale order line
 if the "Force sale quantity" is ticked on the packaging and the "Sell only by packaging" is ticked on product.
 
-For example, if your packaging is set to sell by 5 units and the employee fill
-the quantity with 3, the quantity will be automatically replaced by 5 (it always rounds up).
+For example, 
+- To sell packaging (fill positive product quantities), if your packaging is set to sell by 5 units and the employee fill
+the quantity with 3, the quantity will be automatically replaced by 5 (it always rounds up to the nearest multiple of the packaging quantity).
+
+- To return packaging (fill negative product quantities), if your packaging is set with -5 units and the employee fill
+the quantity with -3, the quantity will be automatically replaced by -5 (it always rounds down to the nearest multiple of the packaging quantity).
 
 .. IMPORTANT::
    This is an alpha version, the data model and design can change at any time without warning.

sell_only_by_packaging/models/product_product.py

@@ -56,5 +56,16 @@ def _convert_packaging_qty(self, qty, uom, packaging):
                 )
                 != 0
             ):
-                qty = qty - (qty % q) + q
+                forced_qty = qty - (qty % q) + q
+                # Support negative rounding
+                if (
+                    float_compare(
+                        qty,
+                        0.0,
+                        precision_rounding=0.001,
+                    )
+                    < 0
+                ):
+                    forced_qty -= q
+                return forced_qty
         return qty

sell_only_by_packaging/readme/DESCRIPTION.rst

@@ -4,8 +4,12 @@ sale orders.
 The creation/update of sale order line will be blocked (by constraints) if the data on the
 sale.order.line does not fit with the configuration of the product's packagings.
 
-It's also possible to force the quantity to sell during creation/modification of the sale order line
+It's also possible to force the quantity to sell/return during creation/modification of the sale order line
 if the "Force sale quantity" is ticked on the packaging and the "Sell only by packaging" is ticked on product.
 
-For example, if your packaging is set to sell by 5 units and the employee fill
-the quantity with 3, the quantity will be automatically replaced by 5 (it always rounds up).
+For example, 
+- To sell packaging (fill positive product quantities), if your packaging is set to sell by 5 units and the employee fill
+the quantity with 3, the quantity will be automatically replaced by 5 (it always rounds up to the nearest multiple of the packaging quantity).
+
+- To return packaging (fill negative product quantities), if your packaging is set with -5 units and the employee fill
+the quantity with -3, the quantity will be automatically replaced by -5 (it always rounds down to the nearest multiple of the packaging quantity).

sell_only_by_packaging/tests/test_sale_only_by_packaging.py

@@ -89,6 +89,31 @@ def test_convert_packaging_qty(self):
                 self.assertAlmostEqual(
                     so_line.product_uom_qty, 220, places=self.precision
                 )
+                # Check with negative quantity
+                so_line.product_uom_qty = -52
+                self.assertAlmostEqual(
+                    so_line.product_uom_qty, -60, places=self.precision
+                )
+                so_line.product_uom_qty = -40
+                self.assertAlmostEqual(
+                    so_line.product_uom_qty, -40, places=self.precision
+                )
+                so_line.product_uom_qty = -38
+                self.assertAlmostEqual(
+                    so_line.product_uom_qty, -40, places=self.precision
+                )
+                so_line.product_uom_qty = -22
+                self.assertAlmostEqual(
+                    so_line.product_uom_qty, -40, places=self.precision
+                )
+                so_line.product_uom_qty = -72
+                self.assertAlmostEqual(
+                    so_line.product_uom_qty, -80, places=self.precision
+                )
+                so_line.product_uom_qty = -209.98
+                self.assertAlmostEqual(
+                    so_line.product_uom_qty, -220, places=self.precision
+                )
 
     def test_onchange_qty_is_not_pack_multiple(self):
         """Check package when qantity is not a multiple of package quantity.