Fix returning tuple subclass from a view function

flask_rest_api/utils.py

@@ -64,14 +64,16 @@ def load_info_from_docstring(docstring):
     return info
 
 
-# Copied from flask
+# Copied from Flask
 def unpack_tuple_response(rv):
     """Unpack a flask Response tuple"""
 
     status = headers = None
 
     # unpack tuple returns
-    if isinstance(rv, tuple):
+    # Unlike Flask, we check exact type because tuple subclasses may be
+    # returned by view functions and paginated/dumped
+    if type(rv) is tuple:  # pylint: disable=unidiomatic-typecheck
         len_rv = len(rv)
 
         # a 3-tuple is unpacked directly

tests/test_blueprint.py

@@ -566,6 +566,13 @@ def func_response_code_str_headers():
         def func_response_wrong_tuple():
             return {}, 201, {'X-header': 'test'}, 'extra'
 
+        @blp.route('/response_tuple_subclass')
+        @blp.response()
+        def func_response_tuple_subclass():
+            class MyTuple(tuple):
+                pass
+            return MyTuple((1, 2))
+
         api.register_blueprint(blp)
 
         response = client.get('/test/response')
@@ -595,6 +602,9 @@ def func_response_wrong_tuple():
         assert response.headers['X-header'] == 'test'
         response = client.get('/test/response_wrong_tuple')
         assert response.status_code == 500
+        response = client.get('/test/response_tuple_subclass')
+        assert response.status_code == 200
+        assert response.json == [1, 2]
 
     def test_blueprint_pagination_response_tuple(self, app):
         api = Api(app)
@@ -631,6 +641,14 @@ def func_response_code_headers():
         def func_response_wrong_tuple():
             return [1, 2], 201, {'X-header': 'test'}, 'extra'
 
+        @blp.route('/response_tuple_subclass')
+        @blp.response()
+        @blp.paginate(Page)
+        def func_response_tuple_subclass():
+            class MyTuple(tuple):
+                pass
+            return MyTuple((1, 2))
+
         api.register_blueprint(blp)
 
         response = client.get('/test/response')
@@ -649,6 +667,9 @@ def func_response_wrong_tuple():
         assert response.headers['X-header'] == 'test'
         response = client.get('/test/response_wrong_tuple')
         assert response.status_code == 500
+        response = client.get('/test/response_tuple_subclass')
+        assert response.status_code == 200
+        assert response.json == [1, 2]
 
     def test_blueprint_response_response_object(self, app, schemas):
         api = Api(app)