Bigint coerce to string (#9775)

* feat: BinIntegerField and COERCE_BIGINT_TO_STRING setting, bigint now can have string api representation

* fix: wrong import location in serializers.py

* feat: updated with changes requests
- typo fix
- value test fix
- import order fix

* Update tests/test_fields.py

* Update docs/api-guide/fields.md

* Update docs/api-guide/fields.md



* refactor: changed BigIntegerField.to_representation simplified + calling super

---------

Co-authored-by: Asif Saif Uddin {"Auvi":"অভি"} <auvipy@gmail.com>

docs/api-guide/fields.md

@@ -269,6 +269,18 @@ Corresponds to `django.db.models.fields.IntegerField`, `django.db.models.fields.
 * `max_value` Validate that the number provided is no greater than this value.
 * `min_value` Validate that the number provided is no less than this value.
 
+## BigIntegerField
+
+A biginteger representation.
+
+Corresponds to `django.db.models.fields.BigIntegerField`.
+
+**Signature**: `BigIntegerField(max_value=None, min_value=None, coerce_to_string=None)`
+
+* `max_value` Validate that the number provided is no greater than this value.
+* `min_value` Validate that the number provided is no less than this value.
+* `coerce_to_string` Set to `True` if string values should be returned for the representation, or `False` if `BigInteger` objects should be returned. Defaults to the same value as the `COERCE_BIGINT_TO_STRING` settings key, which will be `False` unless overridden. If `BigInteger` objects are returned by the serializer, then the final output format will be determined by the renderer.
+
 ## FloatField
 
 A floating point representation.

docs/api-guide/settings.md

@@ -371,6 +371,14 @@ When set to `True`, the serializer `DecimalField` class will return strings inst
 
 Default: `True`
 
+#### COERCE_BIGINT_TO_STRING
+
+When returning biginteger objects in API representations that do not support numbers up to 2^64, it is best to return the value as a string. This avoids the loss of precision that occurs with biginteger implementations.
+
+When set to `True`, the serializer `BigIntegerField` class (by default) will return strings instead of `BigInteger` objects. When set to `False`, serializers will return `BigInteger` objects, which the default JSON encoder will return as numbers.
+
+Default: `False`
+
 ---
 
 ## View names and descriptions

rest_framework/fields.py

@@ -921,6 +921,28 @@ class IntegerField(Field):
         return int(value)
 
 
+class BigIntegerField(IntegerField):
+
+    default_error_messages = {
+        'invalid': _('A valid biginteger is required.'),
+        'max_value': _('Ensure this value is less than or equal to {max_value}.'),
+        'min_value': _('Ensure this value is greater than or equal to {min_value}.'),
+        'max_string_length': _('String value too large.')
+    }
+
+    def __init__(self, coerce_to_string=None, **kwargs):
+        super().__init__(**kwargs)
+
+        if coerce_to_string is not None:
+            self.coerce_to_string = coerce_to_string
+
+    def to_representation(self, value):
+        if getattr(self, 'coerce_to_string', api_settings.COERCE_BIGINT_TO_STRING):
+            return '' if value is None else str(value)
+
+        return super().to_representation(value)
+
+
 class FloatField(Field):
     default_error_messages = {
         'invalid': _('A valid number is required.'),

rest_framework/serializers.py

@@ -53,7 +53,7 @@ from rest_framework.validators import (
 # This helps keep the separation between model fields, form fields, and
 # serializer fields more explicit.
 from rest_framework.fields import (  # NOQA # isort:skip
-    BooleanField, CharField, ChoiceField, DateField, DateTimeField, DecimalField,
+    BigIntegerField, BooleanField, CharField, ChoiceField, DateField, DateTimeField, DecimalField,
     DictField, DurationField, EmailField, Field, FileField, FilePathField, FloatField,
     HiddenField, HStoreField, IPAddressField, ImageField, IntegerField, JSONField,
     ListField, ModelField, MultipleChoiceField, ReadOnlyField,
@@ -906,7 +906,8 @@ class ModelSerializer(Serializer):
     """
     serializer_field_mapping = {
         models.AutoField: IntegerField,
-        models.BigIntegerField: IntegerField,
+        models.BigAutoField: BigIntegerField,
+        models.BigIntegerField: BigIntegerField,
         models.BooleanField: BooleanField,
         models.CharField: CharField,
         models.CommaSeparatedIntegerField: CharField,

rest_framework/settings.py

@@ -116,6 +116,7 @@ DEFAULTS = {
     'COMPACT_JSON': True,
     'STRICT_JSON': True,
     'COERCE_DECIMAL_TO_STRING': True,
+    'COERCE_BIGINT_TO_STRING': False,
     'UPLOADED_FILES_USE_URL': True,
 
     # Browsable API

tests/test_fields.py

@@ -1099,6 +1099,70 @@ class TestMinMaxIntegerField(FieldValues):
     field = serializers.IntegerField(min_value=1, max_value=3)
 
 
+class TestBigIntegerField(FieldValues):
+    """
+    Valid and invalid values for `BigIntegerField`.
+    """
+    valid_inputs = {
+        '1': 1,
+        '0': 0,
+        1: 1,
+        0: 0,
+        123: 123,
+        -123: -123,
+        '999999999999999999999999999': 999999999999999999999999999,
+        -999999999999999999999999999: -999999999999999999999999999,
+        1.0: 1,
+        0.0: 0,
+        '1.0': 1
+    }
+    invalid_inputs = {
+        0.5: ['A valid biginteger is required.'],
+        'abc': ['A valid biginteger is required.'],
+        '0.5': ['A valid biginteger is required.']
+    }
+    outputs = {
+        '1': 1,
+        '0': 0,
+        1: 1,
+        0: 0,
+        1.0: 1,
+        0.0: 0,
+        '999999999999999999999999999': 999999999999999999999999999,
+        -999999999999999999999999999: -999999999999999999999999999
+    }
+    field = serializers.BigIntegerField()
+
+
+class TestMinMaxBigIntegerField(FieldValues):
+    """
+    Valid and invalid values for `BigIntegerField` with min and max limits.
+    """
+    valid_inputs = {
+        '1': 1,
+        '3': 3,
+        1: 1,
+        3: 3,
+    }
+    invalid_inputs = {
+        0: ['Ensure this value is greater than or equal to 1.'],
+        4: ['Ensure this value is less than or equal to 3.'],
+        '0': ['Ensure this value is greater than or equal to 1.'],
+        '4': ['Ensure this value is less than or equal to 3.'],
+    }
+    outputs = {}
+    field = serializers.BigIntegerField(min_value=1, max_value=3)
+
+
+class TestCoercionBigIntegerField(TestCase):
+
+    def test_force_coerce_to_string(self):
+        field = serializers.BigIntegerField(coerce_to_string=True)
+        value = field.to_representation(1)
+        assert isinstance(value, str)
+        assert value == "1"
+
+
 class TestFloatField(FieldValues):
     """
     Valid and invalid values for `FloatField`.

tests/test_model_serializer.py

@@ -171,7 +171,7 @@ class TestRegularFieldMappings(TestCase):
         expected = dedent(r"""
             TestSerializer\(\):
                 auto_field = IntegerField\(read_only=True\)
-                big_integer_field = IntegerField\(.*\)
+                big_integer_field = BigIntegerField\(.*\)
                 boolean_field = BooleanField\(required=False\)
                 char_field = CharField\(max_length=100\)
                 comma_separated_integer_field = CharField\(max_length=100, validators=\[<django.core.validators.RegexValidator object>\]\)