[IMP] purchase : Decrease order quantity should not delete picking and moves

When deacreasing a quantity on a PO it will decrease the quantity
of an associated move. When the move's quantity reach 0, previously the
move was unlinked and aslo the picking if all moves inside were unlinked.

However the destination move(s) still exist with the quantity that has been
removed in the original move. It can confuse the end user which have a move without
origin.

This commit cancel the move/picking instead of unlink them. Thanks to this
the end user still have the link with the original moves and can guess from where
their destinations moves come from. It also remove the filter on PO in order
to display the canceled picking.

addons/purchase/models/purchase.py

@@ -85,7 +85,6 @@ class PurchaseOrder(models.Model):
                 # We keep a limited scope on purpose. Ideally, we should also use move_orig_ids and
                 # do some recursive search, but that could be prohibitive if not done correctly.
                 moves = line.move_ids | line.move_ids.mapped('returned_move_ids')
-                moves = moves.filtered(lambda r: r.state != 'cancel')
                 pickings |= moves.mapped('picking_id')
             order.picking_ids = pickings
             order.picking_count = len(pickings)
@@ -666,12 +665,7 @@ class PurchaseOrderLine(models.Model):
                                 break
                             else:
                                 diff_qty += move.product_qty
-                                move.do_unreserve()
-                                move.state = 'draft'
-                                picking = move.picking_id
-                                move.unlink()
-                                if not picking.move_lines:
-                                    picking.unlink()
+                                move.action_cancel()
                     else:
                         raise UserError('You cannot decrease the ordered quantity below the received quantity.\n'
                                         'Create a return first.')

addons/stock/views/stock_picking_views.xml

@@ -296,7 +296,7 @@
                                     <field name="product_uom_qty" string="Initial Demand" attrs="{'readonly': [('is_initial_demand_editable', '=', False), ('state', '!=', 'draft')]}"/>
                                     <field name="product_uom" attrs="{'readonly': [('state', '!=', 'draft'), ('additional', '=', False)]}" options="{'no_open': True, 'no_create': True}" string="Unit of Measure" groups="product.group_uom"/>
                                     <field name="reserved_availability" string="Reserved"/>
-                                    <field name="quantity_done" string="Done" attrs="{'readonly': [('show_details_visible', '=', True)], 'invisible': ['|', ('state', 'in', ['draft', 'confirmed', 'waiting']), ('show_operations', '=', True)]}"/>
+                                    <field name="quantity_done" string="Done" attrs="{'readonly': ['|', ('show_details_visible', '=', True), ('state', '=', 'cancel')], 'invisible': ['|', ('state', 'in', ['draft', 'confirmed', 'waiting']), ('show_operations', '=', True)]}"/>
                                     <button name="action_show_details" string="Register lots, packs, location" type="object" icon="fa-list" attrs="{'invisible': [('show_details_visible', '=', False)]}"/>
                                 </tree>
                             </field>