From c98e52d80d8deb626fe5f4826cf2872e79a86459 Mon Sep 17 00:00:00 2001
From: Alan Crosswell <alan@crosswell.us>
Date: Mon, 15 Jul 2019 15:18:59 -0400
Subject: [PATCH] Added get_schema_operation_parameters() for DRF OpenAPI
 schema generation. (#1086)

* dummy get_schema_operation_parameters() so DRF generateschema won't throw an exception.

* implement get_schema_operation_parameters()

* Updated release note text.
---
 CHANGES.rst                               |  5 +++++
 django_filters/rest_framework/backends.py | 22 ++++++++++++++++++++++
 docs/guide/rest_framework.txt             |  6 +++---
 tests/rest_framework/test_backends.py     |  9 +++++++++
 4 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index 59d216a4a..45cf24974 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,8 @@
+Version 2.x (unreleased)
+------------------------
+
+* Added ``DjangoFilterBackend.get_schema_operation_parameters()`` for DRF 3.10+ OpenAPI schema generation.
+
 Version 2.1 (2019-1-20)
 -----------------------
 
diff --git a/django_filters/rest_framework/backends.py b/django_filters/rest_framework/backends.py
index f13035adb..eed802a41 100644
--- a/django_filters/rest_framework/backends.py
+++ b/django_filters/rest_framework/backends.py
@@ -138,3 +138,25 @@ def get_schema_fields(self, view):
                 schema=self.get_coreschema_field(field)
             ) for field_name, field in filterset_class.base_filters.items()
         ]
+
+    def get_schema_operation_parameters(self, view):
+        try:
+            queryset = view.get_queryset()
+        except Exception:
+            queryset = None
+            warnings.warn(
+                "{} is not compatible with schema generation".format(view.__class__)
+            )
+
+        filterset_class = self.get_filterset_class(view, queryset)
+        return [] if not filterset_class else [
+            ({
+                'name': field_name,
+                'required': field.extra['required'],
+                'in': 'query',
+                'description': field.label if field.label is not None else field_name,
+                'schema': {
+                    'type': 'string',
+                },
+            }) for field_name, field in filterset_class.base_filters.items()
+        ]
diff --git a/docs/guide/rest_framework.txt b/docs/guide/rest_framework.txt
index 69e336edd..2384049c1 100644
--- a/docs/guide/rest_framework.txt
+++ b/docs/guide/rest_framework.txt
@@ -148,10 +148,10 @@ You can override these methods on a case-by-case basis for each view, creating u
                 'author': self.get_author(),
             }
 
-Schema Generation with Core API
--------------------------------
+Schema Generation with Core API and Open API
+--------------------------------------------
 
-The backend class integrates with DRF's schema generation by implementing ``get_schema_fields()``. This is automatically enabled when Core API is installed. Schema generation usually functions seamlessly, however the implementation does expect to invoke the view's ``get_queryset()`` method. There is a caveat in that views are artificially constructed during schema generation, so the ``args`` and ``kwargs`` attributes will be empty. If you depend on arguments parsed from the URL, you will need to handle their absence in ``get_queryset()``.
+The backend class integrates with DRF's schema generation by implementing ``get_schema_fields()`` and ``get_schema_operation_parameters()``. ``get_schema_fields()`` is automatically enabled when Core API is installed. ``get_schema_operation_parameters()`` is always enabled for Open API (new since DRF 3.9). Schema generation usually functions seamlessly, however the implementation does expect to invoke the view's ``get_queryset()`` method. There is a caveat in that views are artificially constructed during schema generation, so the ``args`` and ``kwargs`` attributes will be empty. If you depend on arguments parsed from the URL, you will need to handle their absence in ``get_queryset()``.
 
 For example, your get queryset method may look like this:
 
diff --git a/tests/rest_framework/test_backends.py b/tests/rest_framework/test_backends.py
index cf5abe841..429ccfc3a 100644
--- a/tests/rest_framework/test_backends.py
+++ b/tests/rest_framework/test_backends.py
@@ -229,6 +229,15 @@ class View(FilterClassRootView):
         self.assertEqual(fields, ['text', 'decimal', 'date', 'f'])
 
 
+class GetSchemaOperationParametersTests(TestCase):
+    def test_get_operation_parameters_with_filterset_fields_list(self):
+        backend = DjangoFilterBackend()
+        fields = backend.get_schema_operation_parameters(FilterFieldsRootView())
+        fields = [f['name'] for f in fields]
+
+        self.assertEqual(fields, ['decimal', 'date'])
+
+
 class TemplateTests(TestCase):
     def test_backend_output(self):
         """