From bcad8947e8192448ab3bd59489444efb567f8793 Mon Sep 17 00:00:00 2001
From: Andrew Baxter <afb2@wustl.edu>
Date: Mon, 3 Jun 2019 20:41:02 +0900
Subject: [PATCH] Support inherited private method names

---
 scrapy/utils/reqser.py     |  9 +++++++--
 tests/test_utils_reqser.py | 16 +++++++++++++++-
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/scrapy/utils/reqser.py b/scrapy/utils/reqser.py
index 40223661f..d1f472e6e 100644
--- a/scrapy/utils/reqser.py
+++ b/scrapy/utils/reqser.py
@@ -81,8 +81,13 @@ def _find_method(obj, func):
             if func_self is obj:
                 name = six.get_method_function(func).__name__
                 if _is_private_method(name):
-                    classname = obj.__class__.__name__.lstrip('_')
-                    name = '_%s%s' % (classname, name)
+                    qualname = getattr(func, '__qualname__', None)
+                    if qualname is None:
+                        classname = obj.__class__.__name__.lstrip('_')
+                        name = '_%s%s' % (classname, name)
+                    else:
+                        splits = qualname.split('.')
+                        name = '_%s%s' % (splits[-2], splits[-1])
                 return name
     raise ValueError("Function %s is not a method of: %s" % (func, obj))
 
diff --git a/tests/test_utils_reqser.py b/tests/test_utils_reqser.py
index fad5b6003..31577bc8c 100644
--- a/tests/test_utils_reqser.py
+++ b/tests/test_utils_reqser.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import unittest
+import sys
 
 from scrapy.http import Request, FormRequest
 from scrapy.spiders import Spider
@@ -74,6 +75,14 @@ class RequestSerializationTest(unittest.TestCase):
                     errback=self.spider.handle_error)
         self._assert_serializes_ok(r, spider=self.spider)
 
+    def test_mixin_private_callback_serialization(self):
+        if sys.version_info[0] < 3:
+            return
+        r = Request("http://www.example.com",
+                    callback=self.spider._TestSpiderMixin__mixin_callback,
+                    errback=self.spider.handle_error)
+        self._assert_serializes_ok(r, spider=self.spider)
+
     def test_private_callback_name_matching(self):
         self.assertTrue(_is_private_method('__a'))
         self.assertTrue(_is_private_method('__a_'))
@@ -106,7 +115,12 @@ class RequestSerializationTest(unittest.TestCase):
         self.assertRaises(ValueError, request_to_dict, r)
 
 
-class TestSpider(Spider):
+class TestSpiderMixin(object):
+    def __mixin_callback(self, response):
+        pass
+
+
+class TestSpider(Spider, TestSpiderMixin):
     name = 'test'
 
     def parse_item(self, response):