Verify SPIDER_MANAGER_CLASS interface in CrawlerRunner

scrapy/crawler.py

@@ -3,9 +3,11 @@ import signal
 import warnings
 
 from twisted.internet import reactor, defer
+from zope.interface.verify import verifyClass
 
 from scrapy.core.engine import ExecutionEngine
 from scrapy.resolver import CachingThreadedResolver
+from scrapy.interfaces import ISpiderManager
 from scrapy.extension import ExtensionManager
 from scrapy.signalmanager import SignalManager
 from scrapy.exceptions import ScrapyDeprecationWarning
@@ -78,6 +80,7 @@ class CrawlerRunner(object):
     def __init__(self, settings):
         self.settings = settings
         smcls = load_object(settings['SPIDER_MANAGER_CLASS'])
+        verifyClass(ISpiderManager, smcls)
         self.spiders = smcls.from_settings(settings.frozencopy())
         self.crawlers = set()
         self._active = set()

tests/test_crawler.py

@@ -2,6 +2,7 @@ import warnings
 import unittest
 
 from twisted.internet import defer
+from zope.interface.verify import DoesNotImplement
 
 from scrapy.crawler import Crawler, CrawlerRunner
 from scrapy.settings import Settings
@@ -42,3 +43,19 @@ class CrawlerTestCase(unittest.TestCase):
 
         self.assertFalse(settings.frozen)
         self.assertTrue(crawler.settings.frozen)
+
+
+def SpiderManagerWithWrongInterface(object):
+
+    def unneeded_method(self):
+        pass
+
+
+class CrawlerRunnerTestCase(unittest.TestCase):
+
+    def test_spider_manager_verify_interface(self):
+        settings = Settings({
+            'SPIDER_MANAGER_CLASS': 'tests.test_crawler.SpiderManagerWithWrongInterface'
+        })
+        with self.assertRaises(DoesNotImplement):
+            CrawlerRunner(settings)