Add docstring and test for async middleware

Author: Cito

README.md

@@ -12,7 +12,7 @@ a query language for APIs created by Facebook.
 [![Python 3 Status](https://pyup.io/repos/github/graphql-python/graphql-core-next/python-3-shield.svg)](https://pyup.io/repos/github/graphql-python/graphql-core-next/)
 
 The current version 1.0.1 of GraphQL-core-next is up-to-date with GraphQL.js version
-14.0.2. All parts of the API are covered by an extensive test suite of currently 1624
+14.0.2. All parts of the API are covered by an extensive test suite of currently 1626
 unit tests.
 
 

graphql/execution/middleware.py

@@ -15,6 +15,9 @@ class MiddlewareManager:
     and/or objects. The functions take the next middleware function as first argument.
     If middleware is provided as an object, it must provide a method `resolve` that is
     used as the middleware function.
+
+    Note that since resolvers return "MaybeAwaitable" values, all middleware functions
+    must be aware of this and check whether values are awaitable before awaiting them.
     """
 
     __slots__ = "middlewares", "_middleware_resolvers", "_cached_resolvers"
@@ -35,7 +38,7 @@ def get_field_resolver(
         """Wrap the provided resolver with the middleware.
 
         Returns a function that chains the middleware functions with the provided
-        resolver function
+        resolver function.
         """
         if self._middleware_resolvers is None:
             return field_resolver

tests/execution/test_middleware.py

@@ -1,4 +1,4 @@
-from pytest import raises
+from pytest import mark, raises
 
 from graphql.execution import MiddlewareManager, execute
 from graphql.language.parser import parse
@@ -55,6 +55,36 @@ def reverse_middleware(next_, *args, **kwargs):
 
             assert result.data == {"first": "eno", "second": "owt"}
 
+        @mark.asyncio
+        async def single_async_function():
+            doc = parse("{ first second }")
+
+            # noinspection PyMethodMayBeStatic
+            class Data:
+                async def first(self, _info):
+                    return "one"
+
+                async def second(self, _info):
+                    return "two"
+
+            test_type = GraphQLObjectType(
+                "TestType",
+                {
+                    "first": GraphQLField(GraphQLString),
+                    "second": GraphQLField(GraphQLString),
+                },
+            )
+
+            async def reverse_middleware(next_, *args, **kwargs):
+                return (await next_(*args, **kwargs))[::-1]
+
+            middlewares = MiddlewareManager(reverse_middleware)
+            result = await execute(
+                GraphQLSchema(test_type), doc, Data(), middleware=middlewares
+            )
+
+            assert result.data == {"first": "eno", "second": "owt"}
+
         def single_object():
             doc = parse("{ first second }")
 
@@ -114,6 +144,46 @@ def resolve(self, next_, *args, **kwargs):
             )
             assert result.data == {"field": "Devloser"}
 
+            middlewares = MiddlewareManager(CaptitalizeMiddleware(), reverse_middleware)
+            result = execute(
+                GraphQLSchema(test_type), doc, Data(), middleware=middlewares
+            )
+            assert result.data == {"field": "devloseR"}
+
+        @mark.asyncio
+        async def with_async_function_and_object():
+            doc = parse("{ field }")
+
+            # noinspection PyMethodMayBeStatic
+            class Data:
+                async def field(self, _info):
+                    return "resolved"
+
+            test_type = GraphQLObjectType(
+                "TestType", {"field": GraphQLField(GraphQLString)}
+            )
+
+            async def reverse_middleware(next_, *args, **kwargs):
+                return (await next_(*args, **kwargs))[::-1]
+
+            class CaptitalizeMiddleware:
+
+                # noinspection PyMethodMayBeStatic
+                async def resolve(self, next_, *args, **kwargs):
+                    return (await next_(*args, **kwargs)).capitalize()
+
+            middlewares = MiddlewareManager(reverse_middleware, CaptitalizeMiddleware())
+            result = await execute(
+                GraphQLSchema(test_type), doc, Data(), middleware=middlewares
+            )
+            assert result.data == {"field": "Devloser"}
+
+            middlewares = MiddlewareManager(CaptitalizeMiddleware(), reverse_middleware)
+            result = await execute(
+                GraphQLSchema(test_type), doc, Data(), middleware=middlewares
+            )
+            assert result.data == {"field": "devloseR"}
+
     def describe_without_manager():
         def no_middleware():
             doc = parse("{ field }")