improved deprecation code; add some test

scrapy/spider.py

@@ -67,9 +67,8 @@ class Spider(object_ref):
 
 class BaseSpider(Spider):
     __metaclass__ = warn_when_subclassed(
-        4,  # == len([object, object_ref, Spider, BaseSpider])
-        "scrapy.spider.BaseSpider was deprecated. "
-        "Please inherit from scrapy.spider.Spider."
+        superclass=Spider,
+        message="scrapy.spider.BaseSpider was deprecated. Please inherit from scrapy.spider.Spider."
     )
 
 

scrapy/tests/test_spider.py

@@ -5,10 +5,11 @@ from cStringIO import StringIO
 
 from twisted.trial import unittest
 
-from scrapy.spider import Spider
+from scrapy.spider import Spider, BaseSpider
 from scrapy.http import Response, TextResponse, XmlResponse, HtmlResponse
 from scrapy.contrib.spiders.init import InitSpider
 from scrapy.contrib.spiders import CrawlSpider, XMLFeedSpider, CSVFeedSpider, SitemapSpider
+from scrapy.exceptions import ScrapyDeprecationWarning
 
 
 class SpiderTest(unittest.TestCase):
@@ -134,5 +135,19 @@ class SitemapSpiderTest(SpiderTest):
         r = Response(url="http://www.example.com/sitemap.xml.gz", body=self.GZBODY)
         self.assertEqual(spider._get_sitemap_body(r), self.BODY)
 
+
+class BaseSpiderDeprecationTest(unittest.TestCase):
+
+    def test_basespider_is_deprecated(self):
+        with warnings.catch_warnings(record=True) as w:
+
+            class MySpider(BaseSpider):
+                pass
+
+            self.assertEqual(len(w), 1)
+            self.assertEqual(w[0].category, ScrapyDeprecationWarning)
+            self.assertEqual(w[0].lineno, inspect.getsourcelines(MySpider)[1])
+
+
 if __name__ == '__main__':
     unittest.main()

scrapy/tests/test_utils_deprecate.py

@@ -0,0 +1,41 @@
+# -*- coding: utf-8 -*-
+from __future__ import absolute_import
+import inspect
+import unittest
+import warnings
+from scrapy.utils.deprecate import warn_when_subclassed
+
+class MyWarning(UserWarning):
+    pass
+
+class SomeBaseClass(object):
+    pass
+
+class NewName(SomeBaseClass):
+    pass
+
+
+class WarnWhenSubclassedTest(unittest.TestCase):
+
+    def test_no_warning_on_definition(self):
+        with warnings.catch_warnings(record=True) as w:
+
+            class Deprecated(NewName):
+                __metaclass__ = warn_when_subclassed(NewName, "message")
+
+        self.assertEqual(w, [])
+
+    def test_warning_on_subclassing(self):
+        with warnings.catch_warnings(record=True) as w:
+
+            class Deprecated(NewName):
+                __metaclass__ = warn_when_subclassed(NewName, "message", MyWarning)
+
+            class UserClass(Deprecated):
+                pass
+
+        self.assertEqual(len(w), 1)
+        msg = w[0]
+        assert issubclass(msg.category, MyWarning)
+        self.assertEqual(str(msg.message), "message")
+        self.assertEqual(msg.lineno, inspect.getsourcelines(UserClass)[1])

scrapy/utils/deprecate.py

@@ -11,14 +11,14 @@ def attribute(obj, oldattr, newattr, version='0.12'):
         (cname, oldattr, version, cname, newattr), ScrapyDeprecationWarning, stacklevel=3)
 
 
-def warn_when_subclassed(mro_len, message, category=ScrapyDeprecationWarning):
+def warn_when_subclassed(superclass, message, category=ScrapyDeprecationWarning):
     """
     Return a metaclass that causes classes to
     issue a warning when they are subclassed.
     """
     class Metaclass(type):
         def __init__(cls, name, bases, clsdict):
-            if len(cls.mro()) > mro_len:
+            if len(cls.mro()) > len(superclass.mro()) + 1:
                 warnings.warn(message, category, stacklevel=2)
             super(Metaclass, cls).__init__(name, bases, clsdict)
     return Metaclass