From acd2b8d43b5ebec7ffd364b6f335427041a0b98d Mon Sep 17 00:00:00 2001
From: NewUserHa <32261870+NewUserHa@users.noreply.github.com>
Date: Thu, 22 Feb 2018 06:37:26 +0800
Subject: [PATCH] [MRG+1] Fix part of issue #3128 - None should not be a valid
 type for 'url' in Response.follow (#3131)

* fix one issue of issue#3128

because @kmike posted: 'If url is '', Scrapy should follow the same page, this is an intended behavior.'

*  fix one issue of issue#3128

because @kmike posted: 'If url is '', Scrapy should follow the same page, this is an intended behavior.'
---
 scrapy/http/response/__init__.py | 2 ++
 tests/test_http_response.py      | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/scrapy/http/response/__init__.py b/scrapy/http/response/__init__.py
index 434d87eab..1974259b5 100644
--- a/scrapy/http/response/__init__.py
+++ b/scrapy/http/response/__init__.py
@@ -120,6 +120,8 @@ class Response(object_ref):
         """
         if isinstance(url, Link):
             url = url.url
+        elif url is None:
+            raise ValueError("url can't be None")
         url = self.urljoin(url)
         return Request(url, callback,
                        method=method,
diff --git a/tests/test_http_response.py b/tests/test_http_response.py
index b228344b5..820758dc9 100644
--- a/tests/test_http_response.py
+++ b/tests/test_http_response.py
@@ -155,6 +155,10 @@ class BaseResponseTest(unittest.TestCase):
         self._assert_followed_url(Link('http://example.com/foo'),
                                   'http://example.com/foo')
 
+    def test_follow_None_url(self):
+        r = self.response_class("http://example.com")
+        self.assertRaises(ValueError, r.follow, None)
+
     def test_follow_whitespace_url(self):
         self._assert_followed_url('foo ',
                                   'http://example.com/foo%20')