Simplified SchedulerMiddlewareManager (to be removed in Scrapy 0.11) by making it inherit from MiddlewareManager

scrapy/core/schedulermw.py

@@ -1,58 +1,31 @@
 """
-This module implements the Scheduler Middleware manager.
-
-For more information see the Scheduler Middleware doc in:
-docs/topics/scheduler-middleware.rst
+Scheduler Middleware manager
 
+TODO: To be removed in Scrapy 0.11
 """
-from collections import defaultdict
+
 from twisted.internet.defer import Deferred
 
-from scrapy import log
-from scrapy.exceptions import NotConfigured
-from scrapy.utils.misc import load_object
+from scrapy.middleware import MiddlewareManager
 from scrapy.utils.defer import mustbe_deferred
 from scrapy.utils.conf import build_component_list
-from scrapy.conf import settings
 
-class SchedulerMiddlewareManager(object):
+class SchedulerMiddlewareManager(MiddlewareManager):
 
-    def __init__(self):
-        self.loaded = False
-        self.enabled = {}
-        self.disabled = {}
-        self.mw_cbs = defaultdict(list)
-        self.load()
+    component_name = 'scheduler middleware'
 
-    def load(self):
-        """Load middleware defined in settings module"""
-        mwlist = build_component_list(settings['SCHEDULER_MIDDLEWARES_BASE'], \
-            settings['SCHEDULER_MIDDLEWARES'])
-        self.enabled.clear()
-        self.disabled.clear()
-        for mwpath in mwlist:
-            try:
-                cls = load_object(mwpath)
-                mw = cls()
-                self.enabled[cls.__name__] = mw
-                self._add_middleware(mw)
-            except NotConfigured, e:
-                self.disabled[cls.__name__] = mwpath
-                if e.args:
-                    log.msg(e)
-        log.msg("Enabled scheduler middlewares: %s" % ", ".join(self.enabled.keys()), \
-            level=log.DEBUG)
-        self.loaded = True
+    @classmethod
+    def _get_mwlist_from_settings(cls, settings):
+        return build_component_list(settings['DOWNLOADER_MIDDLEWARES_BASE'], \
+            settings['DOWNLOADER_MIDDLEWARES'])
 
     def _add_middleware(self, mw):
-        for name in ['enqueue_request', 'open_spider', 'close_spider']:
-            mwfunc = getattr(mw, name, None)
-            if mwfunc:
-                self.mw_cbs[name].append(mwfunc)
+        if hasattr(mw, 'enqueue_request'):
+            self.methods['enqueue_request'].append(mw.enqueue_request)
 
     def enqueue_request(self, wrappedfunc, spider, request):
         def _enqueue_request(request):
-            for mwfunc in self.mw_cbs['enqueue_request']:
+            for mwfunc in self.methods['enqueue_request']:
                 result = mwfunc(spider=spider, request=request)
                 assert result is None or isinstance(result, Deferred), \
                         'Middleware %s.enqueue_request must return None or Deferred, got %s' % \
@@ -63,12 +36,3 @@ class SchedulerMiddlewareManager(object):
 
         deferred = mustbe_deferred(_enqueue_request, request)
         return deferred
-
-    def open_spider(self, spider):
-        for mwfunc in self.mw_cbs['open_spider']:
-            mwfunc(spider)
-
-    def close_spider(self, spider):
-        for mwfunc in self.mw_cbs['close_spider']:
-            mwfunc(spider)
-