Add support for async functions to decorator

Tries to add support for async functions to the decorator, but trips
over not having a failing test to fix.

django_ratelimit/decorators.py

@@ -1,4 +1,5 @@
 from functools import wraps
+from inspect import iscoroutinefunction
 
 from django.conf import settings
 from django.utils.module_loading import import_string
@@ -13,6 +14,23 @@
 
 def ratelimit(group=None, key=None, rate=None, method=ALL, block=True):
     def decorator(fn):
+        # if iscoroutinefunction(fn):
+        #     @wraps(fn)
+        #     async def _async_wrapped(request, *args, **kw):
+        #         old_limited = getattr(request, 'limited', False)
+        #         ratelimited = is_ratelimited(
+        #             request=request, group=group, fn=fn, key=key, rate=rate,
+        #             method=method, increment=True)
+        #         request.limited = ratelimited or old_limited
+        #         if ratelimited and block:
+        #             cls = getattr(
+        #                 settings, 'RATELIMIT_EXCEPTION_CLASS', Ratelimited)
+        #             if isinstance(cls, str):
+        #                 cls = import_string(cls)
+        #             raise cls()
+        #         return await fn(request, *args, **kw)
+        #     return _async_wrapped
+
         @wraps(fn)
         def _wrapped(request, *args, **kw):
             old_limited = getattr(request, 'limited', False)
@@ -23,7 +41,9 @@ def _wrapped(request, *args, **kw):
             if ratelimited and block:
                 cls = getattr(
                     settings, 'RATELIMIT_EXCEPTION_CLASS', Ratelimited)
-                raise (import_string(cls) if isinstance(cls, str) else cls)()
+                if isinstance(cls, str):
+                    cls = import_string(cls)
+                raise cls()
             return fn(request, *args, **kw)
         return _wrapped
     return decorator

django_ratelimit/tests.py

@@ -1,3 +1,4 @@
+import asyncio
 from functools import partial
 
 from django.core.cache import cache, InvalidCacheBackendError
@@ -411,6 +412,24 @@ def view(request):
             req.META['REMOTE_ADDR'] = '2001:db9::1000'
             assert not view(req)
 
+    def test_decorate_async_function(self):
+        event_loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(event_loop)
+
+        @ratelimit(key='ip', rate='1/m', block=False)
+        async def view(request):
+            await asyncio.sleep(0)
+            return request.limited
+
+        req1 = rf.get('/')
+        req1.META['REMOTE_ADDR'] = '1.2.3.4'
+
+        req2 = rf.get('/')
+        req2.META['REMOTE_ADDR'] = '1.2.3.4'
+
+        assert event_loop.run_until_complete(view(req1)) is False
+        assert event_loop.run_until_complete(view(req2)) is True
+
 
 class FunctionsTests(TestCase):
     def setUp(self):