From 0fd72f17ee18506c02b4c0f0e4af368e3bedac3e Mon Sep 17 00:00:00 2001
From: Guilherme Munarolo <guimunarolo@hotmail.com>
Date: Thu, 10 Oct 2019 03:50:20 -0300
Subject: [PATCH] Fixed crash deleting required schema parameter key on PATCH
 requests. (#6944)

Closes #6941
---
 rest_framework/schemas/openapi.py |  4 ++--
 tests/schemas/test_openapi.py     | 25 +++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/rest_framework/schemas/openapi.py b/rest_framework/schemas/openapi.py
index ac846bf80..09a5598f5 100644
--- a/rest_framework/schemas/openapi.py
+++ b/rest_framework/schemas/openapi.py
@@ -387,7 +387,7 @@ class AutoSchema(ViewInspector):
         result = {
             'properties': properties
         }
-        if len(required) > 0:
+        if required:
             result['required'] = required
 
         return result
@@ -463,7 +463,7 @@ class AutoSchema(ViewInspector):
         content = self._map_serializer(serializer)
         # No required fields for PATCH
         if method == 'PATCH':
-            del content['required']
+            content.pop('required', None)
         # No read_only fields for request.
         for name, schema in content['properties'].copy().items():
             if 'readOnly' in schema:
diff --git a/tests/schemas/test_openapi.py b/tests/schemas/test_openapi.py
index d9375585b..e1d29f6fe 100644
--- a/tests/schemas/test_openapi.py
+++ b/tests/schemas/test_openapi.py
@@ -169,6 +169,31 @@ class TestOperationIntrospection(TestCase):
         for response in inspector._get_responses(path, method).values():
             assert 'required' not in response['content']['application/json']['schema']
 
+    def test_empty_required_with_patch_method(self):
+        path = '/'
+        method = 'PATCH'
+
+        class Serializer(serializers.Serializer):
+            read_only = serializers.CharField(read_only=True)
+            write_only = serializers.CharField(write_only=True, required=False)
+
+        class View(generics.GenericAPIView):
+            serializer_class = Serializer
+
+        view = create_view(
+            View,
+            method,
+            create_request(path)
+        )
+        inspector = AutoSchema()
+        inspector.view = view
+
+        request_body = inspector._get_request_body(path, method)
+        # there should be no empty 'required' property, see #6834
+        assert 'required' not in request_body['content']['application/json']['schema']
+        for response in inspector._get_responses(path, method).values():
+            assert 'required' not in response['content']['application/json']['schema']
+
     def test_response_body_generation(self):
         path = '/'
         method = 'POST'