Deprecate Crawler.spiders attribute

docs/topics/api.rst

@@ -76,12 +76,6 @@ how you :ref:`configure the downloader middlewares
         For an introduction on extensions and a list of available extensions on
         Scrapy see :ref:`topics-extensions`.
 
-    .. attribute:: spiders
-
-        The spider manager which takes care of loading spiders.
-
-        Most extensions won't need to access this attribute.
-
     .. attribute:: engine
 
         The execution engine, which coordinates the core crawling logic

scrapy/crawler.py

@@ -1,5 +1,6 @@
 import six
 import signal
+import warnings
 
 from twisted.internet import reactor, defer
 
@@ -7,6 +8,7 @@ from scrapy.core.engine import ExecutionEngine
 from scrapy.resolver import CachingThreadedResolver
 from scrapy.extension import ExtensionManager
 from scrapy.signalmanager import SignalManager
+from scrapy.exceptions import ScrapyDeprecationWarning
 from scrapy.utils.ossignal import install_shutdown_handlers, signal_names
 from scrapy.utils.misc import load_object
 from scrapy import log, signals
@@ -23,14 +25,22 @@ class Crawler(object):
         self.logformatter = lf_cls.from_crawler(self)
         self.extensions = ExtensionManager.from_crawler(self)
 
-        # Attribute kept for backward compatibility (Use CrawlerRunner.spiders)
-        spman_cls = load_object(self.settings['SPIDER_MANAGER_CLASS'])
-        self.spiders = spman_cls.from_settings(self.settings)
-
         self.crawling = False
         self.spider = None
         self.engine = None
 
+    @property
+    def spiders(self):
+        if not hasattr(self, '_spiders'):
+            warnings.warn("Crawler.spiders is deprecated, use "
+                          "CrawlerRunner.spiders or instantiate "
+                          "scrapy.spidermanager.SpiderManager with your "
+                          "settings.",
+                          category=ScrapyDeprecationWarning, stacklevel=2)
+            spman_cls = load_object(self.settings['SPIDER_MANAGER_CLASS'])
+            self._spiders = spman_cls.from_settings(self.settings)
+        return self._spiders
+
     @defer.inlineCallbacks
     def crawl(self, *args, **kwargs):
         assert not self.crawling, "Crawling already taking place"

tests/py3-ignores.txt

@@ -8,6 +8,7 @@ tests/test_contrib_exporter.py
 tests/test_contrib_linkextractors.py
 tests/test_contrib_loader.py
 tests/test_crawl.py
+tests/test_crawler.py
 tests/test_djangoitem/__init__.py
 tests/test_downloader_handlers.py
 tests/test_downloadermiddleware_ajaxcrawlable.py

tests/test_crawler.py

@@ -0,0 +1,24 @@
+import warnings
+import unittest
+
+from scrapy.crawler import Crawler
+from scrapy.settings import Settings
+from scrapy.utils.spider import DefaultSpider
+from scrapy.utils.misc import load_object
+
+
+class CrawlerTestCase(unittest.TestCase):
+
+    def setUp(self):
+        self.crawler = Crawler(DefaultSpider, Settings())
+
+    def test_deprecated_attribute_spiders(self):
+        with warnings.catch_warnings(record=True) as w:
+            spiders = self.crawler.spiders
+            self.assertEqual(len(w), 1)
+            self.assertIn("Crawler.spiders", str(w[0].message))
+            sm_cls = load_object(self.crawler.settings['SPIDER_MANAGER_CLASS'])
+            self.assertIsInstance(spiders, sm_cls)
+
+            self.crawler.spiders
+            self.assertEqual(len(w), 1, "Warn deprecated access only once")