From 9c81721c407ff41ef9dce2c33e26ac477355cf1f Mon Sep 17 00:00:00 2001
From: Andrew Baxter <afb2@wustl.edu>
Date: Wed, 5 Jun 2019 23:43:56 +0900
Subject: [PATCH] Add tests for private method name mangling

---
 scrapy/utils/reqser.py     | 18 +++++++++++-------
 tests/test_utils_reqser.py | 16 +++++++++++++++-
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/scrapy/utils/reqser.py b/scrapy/utils/reqser.py
index d1f472e6e..3c463cfed 100644
--- a/scrapy/utils/reqser.py
+++ b/scrapy/utils/reqser.py
@@ -71,6 +71,16 @@ def _is_private_method(name):
     return name.startswith('__') and not name.endswith('__')
 
 
+def _mangle_private_name(obj, func, name):
+    qualname = getattr(func, '__qualname__', None)
+    if qualname is None:
+        classname = obj.__class__.__name__.lstrip('_')
+        return '_%s%s' % (classname, name)
+    else:
+        splits = qualname.split('.')
+        return '_%s%s' % (splits[-2], splits[-1])
+
+
 def _find_method(obj, func):
     if obj:
         try:
@@ -81,13 +91,7 @@ def _find_method(obj, func):
             if func_self is obj:
                 name = six.get_method_function(func).__name__
                 if _is_private_method(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 _mangle_private_name(obj, func, name)
                 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 31577bc8c..7f9e31daa 100644
--- a/tests/test_utils_reqser.py
+++ b/tests/test_utils_reqser.py
@@ -2,9 +2,11 @@
 import unittest
 import sys
 
+import six
+
 from scrapy.http import Request, FormRequest
 from scrapy.spiders import Spider
-from scrapy.utils.reqser import request_to_dict, request_from_dict, _is_private_method
+from scrapy.utils.reqser import request_to_dict, request_from_dict, _is_private_method, _mangle_private_name
 
 
 class RequestSerializationTest(unittest.TestCase):
@@ -105,6 +107,18 @@ class RequestSerializationTest(unittest.TestCase):
         self.assertFalse(_is_private_method('___'))
         self.assertFalse(_is_private_method('____'))
 
+    def _assert_mangles_to(self, obj, name):
+        self.assertEqual(
+            _mangle_private_name(obj, getattr(obj, name), name),
+            name
+        )
+
+    def test_private_name_mangling(self):
+        self._assert_mangles_to(
+            self.spider, '_TestSpider__parse_item_private')
+        self._assert_mangles_to(
+            self.spider, '_TestSpiderMixin__mixin_callback')
+
     def test_unserializable_callback1(self):
         r = Request("http://www.example.com", callback=lambda x: x)
         self.assertRaises(ValueError, request_to_dict, r)