Merge pull request #196 from CrimsonJacket/feat/allow_for_callbacks_b…

…efore_exception

Allow for callbacks to be called before raising of exceptions

aioresponses/core.py

@@ -179,16 +179,17 @@ def _build_response(self, url: 'Union[URL, str]',
     async def build_response(
         self, url: URL, **kwargs
     ) -> 'Union[ClientResponse, Exception]':
-        if self.exception is not None:
-            return self.exception
-
         if callable(self.callback):
             if asyncio.iscoroutinefunction(self.callback):
                 result = await self.callback(url, **kwargs)
             else:
                 result = self.callback(url, **kwargs)
         else:
             result = None
+
+        if self.exception is not None:
+            return self.exception
+
         result = self if result is None else result
         resp = self._build_response(
             url=url,

tests/test_aioresponses.py

@@ -251,6 +251,15 @@ async def test_raising_exception(self):
             with self.assertRaises(HttpProcessingError):
                 await self.session.get(url)
 
+            callback_called = asyncio.Event()
+            url = 'http://example.com/HttpProcessingError'
+            aiomock.get(url, exception=HttpProcessingError(message='foo'),
+                        callback=lambda *_, **__: callback_called.set())
+            with self.assertRaises(HttpProcessingError):
+                await self.session.get(url)
+
+            await callback_called.wait()
+
     async def test_multiple_requests(self):
         """Ensure that requests are saved the way they would have been sent."""
         with aioresponses() as m: