Round quantity computing in search clause

The internal quantity is stored without precision constraint and so the sum
result of many rows cumulate the rounding issue.
So the quantity must be rounded to return correct result when operator is
equality.
But as getting the digits from the product default uom would require to make
many joins, the simplest and more efficient solution is to use the highest
digits of the units.

issue11235
review390001002
(grafted from 4b8495cb0efdfb71f11a7520967ed5ef9d9dfca9)

--HG--
branch : 6.0

move.py

@@ -8,8 +8,9 @@ from collections import OrderedDict, defaultdict
 from itertools import groupby
 
 from sql import Literal, Union, Column, Null, For
-from sql.aggregate import Sum
+from sql.aggregate import Max, Sum
 from sql.conditionals import Coalesce, Case
+from sql.functions import Round
 
 from trytond.i18n import gettext
 from trytond.model import Workflow, Model, ModelView, ModelSQL, fields, Check
@@ -119,6 +120,8 @@ class StockMixin(object):
         pool = Pool()
         Product = pool.get('product.product')
         Move = pool.get('stock.move')
+        Uom = pool.get('product.uom')
+        uom = Uom.__table__()
 
         if not location_ids or not domain:
             return []
@@ -136,7 +139,12 @@ class StockMixin(object):
                 query = Move.compute_quantities_query(
                     location_ids, with_childs, grouping=grouping)
                 col_id = Column(query, grouping[position])
-                quantity = Sum(query.quantity)
+                # We need to round the result to have same result as
+                # products_by_location but as we do not have the unit, we use
+                # the biggest digits of all unit as best approximation.
+                quantity = Round(
+                    fields.Numeric('quantity').sql_cast(Sum(query.quantity)),
+                    uom.select(Max(uom.digits)))
                 group_by = [Column(query, key).as_(key) for key in grouping]
                 return [('id', 'in', query.select(
                             col_id,