async def support in pipelines

pytest.ini

@@ -95,6 +95,7 @@ flake8-ignore =
     scrapy/loader/__init__.py E501 E128
     scrapy/loader/processors.py E501
     # scrapy/pipelines
+    scrapy/pipelines/__init__.py E501
     scrapy/pipelines/files.py E116 E501 E266
     scrapy/pipelines/images.py E265 E501
     scrapy/pipelines/media.py E125 E501 E266

scrapy/pipelines/__init__.py

@@ -6,6 +6,7 @@
 
 from scrapy.middleware import MiddlewareManager
 from scrapy.utils.conf import build_component_list
+from scrapy.utils.defer import deferred_f_from_coro_f
 
 
 class ItemPipelineManager(MiddlewareManager):
@@ -19,7 +20,7 @@ def _get_mwlist_from_settings(cls, settings):
     def _add_middleware(self, pipe):
         super(ItemPipelineManager, self)._add_middleware(pipe)
         if hasattr(pipe, 'process_item'):
-            self.methods['process_item'].append(pipe.process_item)
+            self.methods['process_item'].append(deferred_f_from_coro_f(pipe.process_item))
 
     def process_item(self, item, spider):
         return self._process_chain('process_item', item, spider)

scrapy/utils/defer.py

@@ -2,6 +2,7 @@
 Helper functions for dealing with Twisted deferreds
 """
 import asyncio
+from functools import wraps
 import inspect
 
 from twisted.internet import defer, task
@@ -140,3 +141,15 @@ def deferred_from_coro(o):
             # wrapping the coroutine into a Future and then into a Deferred, this requires AsyncioSelectorReactor
             return defer.Deferred.fromFuture(asyncio.ensure_future(o))
     return o
+
+
+def deferred_f_from_coro_f(coro_f):
+    """ Converts a coroutine function into a function that returns a Deferred.
+
+    The coroutine function will be called at the time when the wrapper is called. Wrapper args will be passed to it.
+    This is useful for callback chains, as callback functions are called with the previous callback result.
+    """
+    @wraps(coro_f)
+    def f(*coro_args, **coro_kwargs):
+        return deferred_from_coro(coro_f(*coro_args, **coro_kwargs))
+    return f

tests/test_pipelines.py

@@ -1,9 +1,12 @@
+import asyncio
+
+from pytest import mark
 from twisted.internet import defer
 from twisted.internet.defer import Deferred
 from twisted.trial import unittest
 
 from scrapy import Spider, signals, Request
-from scrapy.utils.test import get_crawler
+from scrapy.utils.test import get_crawler, get_from_asyncio_queue
 
 from tests.mockserver import MockServer
 
@@ -26,6 +29,20 @@ def process_item(self, item, spider):
         return d
 
 
+class AsyncDefPipeline:
+    async def process_item(self, item, spider):
+        await defer.succeed(42)
+        item['pipeline_passed'] = True
+        return item
+
+
+class AsyncDefAsyncioPipeline:
+    async def process_item(self, item, spider):
+        await asyncio.sleep(0.2)
+        item['pipeline_passed'] = await get_from_asyncio_queue(True)
+        return item
+
+
 class ItemSpider(Spider):
     name = 'itemspider'
 
@@ -69,3 +86,16 @@ def test_deferred_pipeline(self):
         crawler = self._create_crawler(DeferredPipeline)
         yield crawler.crawl(mockserver=self.mockserver)
         self.assertEqual(len(self.items), 1)
+
+    @defer.inlineCallbacks
+    def test_asyncdef_pipeline(self):
+        crawler = self._create_crawler(AsyncDefPipeline)
+        yield crawler.crawl(mockserver=self.mockserver)
+        self.assertEqual(len(self.items), 1)
+
+    @mark.only_asyncio()
+    @defer.inlineCallbacks
+    def test_asyncdef_asyncio_pipeline(self):
+        crawler = self._create_crawler(AsyncDefAsyncioPipeline)
+        yield crawler.crawl(mockserver=self.mockserver)
+        self.assertEqual(len(self.items), 1)