From be86d67b16fb73ef06b8c4a5890894b03047bd9b Mon Sep 17 00:00:00 2001
From: Ryan P Kilby <kilbyr@gmail.com>
Date: Mon, 1 Jul 2019 19:04:15 -0700
Subject: [PATCH] Fix ModelField.max_length handling

---
 rest_framework/fields.py |  4 ++--
 tests/test_fields.py     | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 77767b2c5..f5f0b632e 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -1888,9 +1888,9 @@ class ModelField(Field):
         self.model_field = model_field
         # The `max_length` option is supported by Django's base `Field` class,
         # so we'd better support it here.
-        max_length = kwargs.pop('max_length', None)
+        self.max_length = kwargs.pop('max_length', None)
         super().__init__(**kwargs)
-        if max_length is not None:
+        if self.max_length is not None:
             message = lazy_format(self.error_messages['max_length'], max_length=self.max_length)
             self.validators.append(
                 MaxLengthValidator(self.max_length, message=message))
diff --git a/tests/test_fields.py b/tests/test_fields.py
index db6484a7d..7c495cd63 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -2247,6 +2247,21 @@ class TestSerializerMethodField:
         assert field.method_name == 'get_example_field'
 
 
+# Tests for ModelField.
+# ---------------------
+
+class TestModelField:
+    def test_max_length_init(self):
+        field = serializers.ModelField(None)
+        assert len(field.validators) == 0
+
+        field = serializers.ModelField(None, max_length=10)
+        assert len(field.validators) == 1
+
+
+# Tests for validation errors
+# ---------------------------
+
 class TestValidationErrorCode:
     @pytest.mark.parametrize('use_list', (False, True))
     def test_validationerror_code_with_msg(self, use_list):