Possibility to remove trailing zeros on DecimalFields representation (#6514)

* Added normalize parameter to DecimalField to be able to strip trailing zeros. Fixes #6151.

* Updated docs to include normalize option on DecimalField

* Fixed linting error in test_fields

* Removed comment and renamed normalize to normalize_output as suggested in code review

Co-authored-by: Tom Christie <tom@tomchristie.com>

docs/api-guide/fields.md

@@ -295,6 +295,7 @@ Corresponds to `django.db.models.fields.DecimalField`.
 * `min_value` Validate that the number provided is no less than this value.
 * `localize` Set to `True` to enable localization of input and output based on the current locale. This will also force `coerce_to_string` to `True`. Defaults to `False`. Note that data formatting is enabled if you have set `USE_L10N=True` in your settings file.
 * `rounding` Sets the rounding mode used when quantising to the configured precision. Valid values are [`decimal` module rounding modes][python-decimal-rounding-modes]. Defaults to `None`.
+* `normalize_output` Will normalize the decimal value when serialized. This will strip all trailing zeroes and change the value's precision to the minimum required precision to be able to represent the value without loosing data. Defaults to `False`.
 
 #### Example usage
 

rest_framework/fields.py

@@ -963,10 +963,11 @@ class DecimalField(Field):
     MAX_STRING_LENGTH = 1000  # Guard against malicious string inputs.
 
     def __init__(self, max_digits, decimal_places, coerce_to_string=None, max_value=None, min_value=None,
-                 localize=False, rounding=None, **kwargs):
+                 localize=False, rounding=None, normalize_output=False, **kwargs):
         self.max_digits = max_digits
         self.decimal_places = decimal_places
         self.localize = localize
+        self.normalize_output = normalize_output
         if coerce_to_string is not None:
             self.coerce_to_string = coerce_to_string
         if self.localize:
@@ -1079,6 +1080,9 @@ class DecimalField(Field):
 
         quantized = self.quantize(value)
 
+        if self.normalize_output:
+            quantized = quantized.normalize()
+
         if not coerce_to_string:
             return quantized
         if self.localize:

tests/test_fields.py

@@ -1251,6 +1251,27 @@ class TestQuantizedValueForDecimal(TestCase):
         assert value == expected_digit_tuple
 
 
+class TestNormalizedOutputValueDecimalField(TestCase):
+    """
+    Test that we get the expected behavior of on DecimalField when normalize=True
+    """
+
+    def test_normalize_output(self):
+        field = serializers.DecimalField(max_digits=4, decimal_places=3, normalize_output=True)
+        output = field.to_representation(Decimal('1.000'))
+        assert output == '1'
+
+    def test_non_normalize_output(self):
+        field = serializers.DecimalField(max_digits=4, decimal_places=3, normalize_output=False)
+        output = field.to_representation(Decimal('1.000'))
+        assert output == '1.000'
+
+    def test_normalize_coeherce_to_string(self):
+        field = serializers.DecimalField(max_digits=4, decimal_places=3, normalize_output=True, coerce_to_string=False)
+        output = field.to_representation(Decimal('1.000'))
+        assert output == Decimal('1')
+
+
 class TestNoDecimalPlaces(FieldValues):
     valid_inputs = {
         '0.12345': Decimal('0.12345'),