DecimalValidator fails to validate 0 in scientific notation (0E+1 or 0E+2)

[Shiplu Mokaddim]

In 1.11.29 DecimalValidator treats 0E+1 as valid decimal

>>> from django.forms.fields import DecimalField
>>> DecimalField(max_digits=8, decimal_places=7).clean('0E+1')
Decimal('0E+1')

But in 2.0.13 it raises ValidatorError.

>>> DecimalField(max_digits=8, decimal_places=7).clean('0E+1')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/amokaddim/e/fh/lib/python3.8/site-packages/django/forms/fields.py", line 150, in clean
    self.run_validators(value)
  File "/Users/amokaddim/e/fh/lib/python3.8/site-packages/django/forms/fields.py", line 141, in run_validators
    raise ValidationError(errors)
django.core.exceptions.ValidationError: <exception str() failed>

This was introduced in ​https://github.com/django/django/commit/7c6590af5f199c9ede970758877b5c1eb7e9b3a6#diff-d9609d8dc8482b30eac30df16213cba134562949fd62c97573927b89e880f85b

Is there any way I can prevent this validation error from happening in Django 2.0? Any flag or option that will prevent this?

Calling Decimal('0E+1').normalize() inside to_python method solves the problem. But that's a workaround!

Here is a reproducible test case.

from unittest import TestCase
from decimal import Decimal
from django.core.validators import DecimalValidator
from django.core.exceptions import ValidationError

class Test(TestCase):
    def test(self):
        value = '0E+1'
        validator = DecimalValidator(8, 7)
        try:
            validator(Decimal(value))
        except ValidationError:
            self.fail("'{}' is an invalid decimal".format(value))

[Mariusz Felisiak]

Thanks for the report. We should fix an edge case with 0, maybe:

django/core/validators.py

@@ -487 +487 @@
             )
         if exponent >= 0:
             # A positive exponent adds that many trailing zeros.
-            digits = len(digit_tuple) + exponent
+            digits = len(digit_tuple)
+            if digit_tuple != (0,):
+                digits += exponent
             decimals = 0
         else:
             # If the absolute value of the negative exponent is larger than the

[Kamil Turek]

​PR

[Mariusz Felisiak]

You shouldn't mark your own PRs as RFC (see ​docs).

[Mariusz Felisiak <felisiak.mariusz@…>]

In ae509f8f:

Fixed #34014 -- Fixed DecimalValidator validating 0 in positive exponent scientific notation.

Thanks Shiplu Mokaddim for the report.