Handle enum type for nested ChoiceFields (#400)

requirements/test.txt

@@ -5,5 +5,7 @@ pytest-cov>=2.6.0
 pytest-xdist>=1.25.0
 pytest-django>=3.4.4
 datadiff==2.0.0
+psycopg2-binary==2.8.3
+django-fake-model==0.1.4
 
 -r testproj.txt

src/drf_yasg/inspectors/field.py

@@ -656,7 +656,11 @@ def field_to_swagger_object(self, field, swagger_object_type, use_references, **
             serializer = get_parent_serializer(field)
             if isinstance(serializer, serializers.ModelSerializer):
                 model = getattr(getattr(serializer, 'Meta'), 'model')
-                model_field = get_model_field(model, field.source)
+                # Use the parent source for nested fields
+                model_field = get_model_field(model, field.source or field.parent.source)
+                # If the field has a base_field its type must be used
+                if getattr(model_field, "base_field", None):
+                    model_field = model_field.base_field
                 if model_field:
                     model_type = get_basic_type_info(model_field)
                     if model_type:

tests/test_schema_generator.py

@@ -3,11 +3,14 @@
 
 import pytest
 from django.conf.urls import url
+from django.contrib.postgres import fields as postgres_fields
+from django.db import models
 from django.utils.inspect import get_func_args
 from rest_framework import routers, serializers, viewsets
 from rest_framework.decorators import api_view
 from rest_framework.response import Response
 
+from django_fake_model import models as fake_models
 from drf_yasg import codecs, openapi
 from drf_yasg.codecs import yaml_sane_load
 from drf_yasg.errors import SwaggerGenerationError
@@ -230,3 +233,43 @@ def retrieve(self, request, pk=None):
     property_schema = swagger['definitions']['Detail']['properties']['detail']
 
     assert property_schema == openapi.Schema(title='Detail', type=expected_type, enum=choices)
+
+
+@pytest.mark.parametrize('choices, field, expected_type', [
+    ([1, 2, 3], models.IntegerField, openapi.TYPE_INTEGER),
+    (["A", "B"], models.CharField, openapi.TYPE_STRING),
+])
+def test_nested_choice_in_array_field(choices, field, expected_type):
+
+    # Create a model class on the fly to avoid warnings about using the several
+    # model class name several times
+    model_class = type(
+        "%sModel" % field.__name__,
+        (fake_models.FakeModel,),
+        {
+            "array": postgres_fields.ArrayField(
+                field(choices=((i, "choice %s" % i) for i in choices))
+            ),
+            "__module__": "test_models",
+        }
+    )
+
+    class ArraySerializer(serializers.ModelSerializer):
+        class Meta:
+            model = model_class
+            fields = ("array",)
+
+    class ArrayViewSet(viewsets.ModelViewSet):
+        serializer_class = ArraySerializer
+
+    router = routers.DefaultRouter()
+    router.register(r'arrays', ArrayViewSet, **_basename_or_base_name('arrays'))
+
+    generator = OpenAPISchemaGenerator(
+        info=openapi.Info(title='Test array model generator', default_version='v1'),
+        patterns=router.urls
+    )
+
+    swagger = generator.get_schema(None, True)
+    property_schema = swagger['definitions']['Array']['properties']['array']['items']
+    assert property_schema == openapi.Schema(title='Array', type=expected_type, enum=choices)