From 48f3db36d61d828e44ec36905386b59b3b049cd3 Mon Sep 17 00:00:00 2001
From: Tom Christie <tom@tomchristie.com>
Date: Wed, 10 Aug 2016 14:39:26 +0100
Subject: [PATCH] Allow optional max_digits on DecimalField (#4377)

---
 rest_framework/fields.py |  3 ++-
 tests/test_fields.py     | 12 ++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index b4346cd85..3a2f27205 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -1016,7 +1016,8 @@ class DecimalField(Field):
             return value
 
         context = decimal.getcontext().copy()
-        context.prec = self.max_digits
+        if self.max_digits is not None:
+            context.prec = self.max_digits
         return value.quantize(
             decimal.Decimal('.1') ** self.decimal_places,
             context=context
diff --git a/tests/test_fields.py b/tests/test_fields.py
index 60f02777a..1cbff9909 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -876,6 +876,18 @@ class TestMinMaxDecimalField(FieldValues):
     )
 
 
+class TestNoMaxDigitsDecimalField(FieldValues):
+    field = serializers.DecimalField(
+        max_value=100, min_value=0,
+        decimal_places=2, max_digits=None
+    )
+    valid_inputs = {
+        '10': Decimal('10.00')
+    }
+    invalid_inputs = {}
+    outputs = {}
+
+
 class TestNoStringCoercionDecimalField(FieldValues):
     """
     Output values for `DecimalField` with `coerce_to_string=False`.