Compute digits of float value before applying factor

When applying the factor, we introduce new rounding issue which falsify the
computation of digits.
So it is better to compute the digits using the initial value (coming from the
string parsing) and update the digits based on the order of the factor.

Closes #13964

sao/src/common.js

@@ -2138,8 +2138,7 @@
                     return '';
                 }
                 var digit = 0;
-                var factor = Number(field.factor || 1);
-                var string = String(value * factor);
+                var string = String(value);
                 if (string.contains('e')) {
                     var exp = string.split('e')[1];
                     string = string.split('e')[0];
@@ -2148,6 +2147,8 @@
                 if (string.contains('.')) {
                     digit += string.replace(/0+$/, '').split('.')[1].length;
                 }
+                var factor = Number(field.factor || 1);
+                digit -= Math.round(Math.log10(factor));
                 return (value * factor).toFixed(digit);
             };
             var format_selection = function() {

tryton/tryton/common/domain_parser.py

@@ -5,6 +5,7 @@ import decimal
 import gettext
 import io
 import locale
+import math
 from collections import OrderedDict
 from decimal import Decimal
 from shlex import shlex
@@ -336,17 +337,18 @@ def format_value(field, value, target=None, context=None, _quote_empty=False):
                     or isinstance(value, bool))):
             return ''
         digit = 0
-        if isinstance(value, Decimal):
-            cast = Decimal
-        else:
-            cast = float
-        factor = cast(field.get('factor', 1))
-        string_ = str(value * factor)
+        string_ = str(value)
         if 'e' in string_:
             string_, exp = string_.split('e')
             digit -= int(exp)
         if '.' in string_:
             digit += len(string_.rstrip('0').split('.')[1])
+        if isinstance(value, Decimal):
+            cast = Decimal
+        else:
+            cast = float
+        factor = cast(field.get('factor', 1))
+        digit -= round(math.log10(factor))
         return locale.localize(
             '{0:.{1}f}'.format(value * factor or 0, digit), True)