feat: Add no_leading_zeroes kwarg to Number

Author: jpmckinney

CHANGELOG.rst

@@ -1,3 +1,8 @@
+1.12.0 - July 29, 2024
+----------------------
+
+-  feat: :class:`.Number` accepts a ``no_leading_zeroes`` keyword argument, to indicate whether to disallow numbers with leading zeroes (not including a single zero, or a single zero before a decimal).
+
 1.11.0 - May 27, 2024
 ---------------------
 

agate/data_types/number.py

@@ -29,14 +29,16 @@ class Number(DataType):
         provided by the specified :code:`locale`.
     :param currency_symbols:
         A sequence of currency symbols to strip from numbers.
+    :param no_leading_zeroes:
+        Whether to disallow leading zeroes.
     """
     def __init__(self, locale='en_US', group_symbol=None, decimal_symbol=None,
-                 currency_symbols=DEFAULT_CURRENCY_SYMBOLS, **kwargs):
+                 currency_symbols=DEFAULT_CURRENCY_SYMBOLS, no_leading_zeroes=None, **kwargs):
         super().__init__(**kwargs)
 
         self.locale = Locale.parse(locale)
-
         self.currency_symbols = currency_symbols
+        self.no_leading_zeroes = no_leading_zeroes
 
         # Suppress Babel warning on Python 3.6
         # See #665
@@ -91,6 +93,9 @@ def cast(self, d):
         d = d.replace(self.group_symbol, '')
         d = d.replace(self.decimal_symbol, '.')
 
+        if self.no_leading_zeroes and len(d) > 1 and d[0] == '0' and d[1] != '.':
+            raise CastError('Can not parse value "%s" as Decimal without leading zeroes' % d)
+
         try:
             return Decimal(d) * sign
         # The Decimal class will return an InvalidOperation exception on most Python implementations,

tests/test_data_types.py

@@ -188,6 +188,19 @@ def test_cast_error(self):
         with self.assertRaises(CastError):
             self.type.cast('quack')
 
+    def test_cast_error_leading_zeroes(self):
+        data_type = Number(no_leading_zeroes=True)
+
+        self.assertEqual(data_type.cast('0'), Decimal('0'))
+        self.assertEqual(data_type.cast('0.123'), Decimal('0.123'))
+        self.assertEqual(data_type.cast('123'), Decimal('123'))
+
+        with self.assertRaises(CastError):
+            data_type.cast('01')
+
+        with self.assertRaises(CastError):
+            data_type.cast('00.11')
+
 
 class TestDate(unittest.TestCase):
     def setUp(self):