[IMP] base: tools: Added json_round to round into json suitable representation

X-original-commit: 415c06362c7ecea9472acf8da2ff75615eedb392
Part-of: odoo/odoo#92195

odoo/tools/float_utils.py

@@ -215,6 +215,35 @@ def float_split(value, precision_digits):
         return int(units), 0
     return int(units), int(cents)
 
+def json_float_round(value, precision_digits, rounding_method='HALF-UP'):
+    """Not suitable for float calculations! Similar to float_repr except that it
+    returns a float suitable for json dump
+
+    This may be necessary to produce "exact" representations of rounded float
+    values during serialization, such as what is done by `json.dumps()`.
+    Unfortunately `json.dumps` does not allow any form of custom float representation,
+    nor any custom types, everything is serialized from the basic JSON types.
+
+    :param int precision_digits: number of fractional digits to round to.
+    :param rounding_method: the rounding method used: 'HALF-UP', 'UP' or 'DOWN',
+           the first one rounding up to the closest number with the rule that
+           number>=0.5 is rounded up to 1, the second always rounding up and the
+           latest one always rounding down.
+    :return: a rounded float value that must not be used for calculations, but
+             is ready to be serialized in JSON with minimal chances of
+             representation errors.
+    """
+    rounded_value = float_round(f, precision_digits=precision_digits, rounding_method=rounding_method)
+    rounded_repr = float_repr(rounded_value, precision_digits=precision_digits)
+    # As of Python 3.1, rounded_repr should be the shortest representation for our
+    # rounded float, so we create a new float whose repr is expected
+    # to be the same value, or a value that is semantically identical
+    # and will be used in the json serialization.
+    # e.g. if rounded_repr is '3.1750', the new float repr could be 3.175
+    # but not 3.174999999999322452.
+    # Cfr. bpo-1580: https://bugs.python.org/issue1580
+    return float(rounded_repr)
+
 
 if __name__ == "__main__":