Merge pull request #4331 from Gallaecio/response-cb-kwargs

Implement Response.cb_kwargs

docs/topics/request-response.rst

@@ -672,6 +672,18 @@ Response objects
 
         .. seealso:: :attr:`Request.meta` attribute
 
+    .. attribute:: Response.cb_kwargs
+
+        A shortcut to the :attr:`Request.cb_kwargs` attribute of the
+        :attr:`Response.request` object (i.e. ``self.request.cb_kwargs``).
+
+        Unlike the :attr:`Response.request` attribute, the
+        :attr:`Response.cb_kwargs` attribute is propagated along redirects and
+        retries, so you will get the original :attr:`Request.cb_kwargs` sent
+        from your spider.
+
+        .. seealso:: :attr:`Request.cb_kwargs` attribute
+
     .. attribute:: Response.flags
 
         A list that contains flags for this response. Flags are labels used for

scrapy/http/response/__init__.py

@@ -25,6 +25,16 @@ class Response(object_ref):
         self.request = request
         self.flags = [] if flags is None else list(flags)
 
+    @property
+    def cb_kwargs(self):
+        try:
+            return self.request.cb_kwargs
+        except AttributeError:
+            raise AttributeError(
+                "Response.cb_kwargs not available, this response "
+                "is not tied to any request"
+            )
+
     @property
     def meta(self):
         try:

tests/test_http_response.py

@@ -72,6 +72,22 @@ class BaseResponseTest(unittest.TestCase):
         r1 = self.response_class("http://www.example.com", body=b"Some body", request=req)
         assert r1.meta is req.meta
 
+    def test_copy_cb_kwargs(self):
+        req = Request("http://www.example.com")
+        req.cb_kwargs['foo'] = 'bar'
+        r1 = self.response_class("http://www.example.com", body=b"Some body", request=req)
+        assert r1.cb_kwargs is req.cb_kwargs
+
+    def test_unavailable_meta(self):
+        r1 = self.response_class("http://www.example.com", body=b"Some body")
+        with self.assertRaisesRegex(AttributeError, r'Response\.meta not available'):
+            r1.meta
+
+    def test_unavailable_cb_kwargs(self):
+        r1 = self.response_class("http://www.example.com", body=b"Some body")
+        with self.assertRaisesRegex(AttributeError, r'Response\.cb_kwargs not available'):
+            r1.cb_kwargs
+
     def test_copy_inherited_classes(self):
         """Test Response children copies preserve their class"""