Add cb_kwargs option to the parse command

docs/topics/commands.rst

@@ -461,6 +461,9 @@ Supported options:
 * ``--meta`` or ``-m``: additional request meta that will be passed to the callback 
   request. This must be a valid json string. Example: --meta='{"foo" : "bar"}'
 
+* ``--cb_kwargs``: additional keyword arguments that will be passed to the callback.
+  This must be a valid json string. Example: --cb_kwargs='{"foo" : "bar"}'
+
 * ``--pipelines``: process items through pipelines
 
 * ``--rules`` or ``-r``: use :class:`~scrapy.spiders.CrawlSpider`

scrapy/commands/parse.py

@@ -51,12 +51,13 @@ class Command(ScrapyCommand):
             help="use this callback for parsing, instead looking for a callback")
         parser.add_option("-m", "--meta", dest="meta",
             help="inject extra meta into the Request, it must be a valid raw json string")
+        parser.add_option("--cb_kwargs", dest="cb_kwargs",
+            help="inject extra cb_kwargs into the Request, it must be a valid raw json string")
         parser.add_option("-d", "--depth", dest="depth", type="int", default=1,
             help="maximum depth for parsing requests [default: %default]")
         parser.add_option("-v", "--verbose", dest="verbose", action="store_true",
             help="print each depth level one by one")
 
-
     @property
     def max_level(self):
         levels = list(self.items.keys()) + list(self.requests.keys())
@@ -111,10 +112,11 @@ class Command(ScrapyCommand):
             if not opts.nolinks:
                 self.print_requests(colour=colour)
 
-    def run_callback(self, response, cb):
+    def run_callback(self, response, callback, cb_kwargs=None):
+        cb_kwargs = cb_kwargs or {}
         items, requests = [], []
 
-        for x in iterate_spider_output(cb(response)):
+        for x in iterate_spider_output(callback(response, **cb_kwargs)):
             if isinstance(x, (BaseItem, dict)):
                 items.append(x)
             elif isinstance(x, Request):
@@ -142,8 +144,7 @@ class Command(ScrapyCommand):
         else:
             self.spidercls = spidercls_for_request(spider_loader, Request(url))
             if not self.spidercls:
-                logger.error('Unable to find spider for: %(url)s',
-                             {'url': url})
+                logger.error('Unable to find spider for: %(url)s', {'url': url})
 
         # Request requires callback argument as callable or None, not string
         request = Request(url, None)
@@ -160,7 +161,7 @@ class Command(ScrapyCommand):
                          {'url': url})
 
     def prepare_request(self, spider, request, opts):
-        def callback(response):
+        def callback(response, **cb_kwargs):
             # memorize first request
             if not self.first_response:
                 self.first_response = response
@@ -175,7 +176,7 @@ class Command(ScrapyCommand):
 
                     if not cb:
                         logger.error('Cannot find a rule that matches %(url)r in spider: %(spider)s',
-                                 {'url': response.url, 'spider': spider.name})
+                                     {'url': response.url, 'spider': spider.name})
                         return
                 else:
                     cb = 'parse'
@@ -192,7 +193,7 @@ class Command(ScrapyCommand):
             # parse items and requests
             depth = response.meta['_depth']
 
-            items, requests = self.run_callback(response, cb)
+            items, requests = self.run_callback(response, cb, cb_kwargs)
             if opts.pipelines:
                 itemproc = self.pcrawler.engine.scraper.itemproc
                 for item in items:
@@ -207,10 +208,14 @@ class Command(ScrapyCommand):
                     req.callback = callback
                 return requests
 
-        #update request meta if any extra meta was passed through the --meta/-m opts.
+        # update request meta if any extra meta was passed through the --meta/-m opts.
         if opts.meta:
             request.meta.update(opts.meta)
 
+        # update cb_kwargs if any extra cb_kwargs was passed through the --cb_kwargs option.
+        if opts.cb_kwargs:
+            request.cb_kwargs.update(opts.cb_kwargs)
+
         request.meta['_depth'] = 1
         request.meta['_callback'] = request.callback
         request.callback = callback
@@ -221,23 +226,29 @@ class Command(ScrapyCommand):
 
         self.process_spider_arguments(opts)
         self.process_request_meta(opts)
+        self.process_request_cb_kwargs(opts)
 
     def process_spider_arguments(self, opts):
-
         try:
             opts.spargs = arglist_to_dict(opts.spargs)
         except ValueError:
             raise UsageError("Invalid -a value, use -a NAME=VALUE", print_help=False)
 
     def process_request_meta(self, opts):
-
         if opts.meta:
             try:
                 opts.meta = json.loads(opts.meta)
             except ValueError:
-                raise UsageError("Invalid -m/--meta value, pass a valid json string to -m or --meta. " \
-                                "Example: --meta='{\"foo\" : \"bar\"}'", print_help=False)
+                raise UsageError("Invalid -m/--meta value, pass a valid json string to -m or --meta. "
+                                 "Example: --meta='{\"foo\" : \"bar\"}'", print_help=False)
 
+    def process_request_cb_kwargs(self, opts):
+        if opts.cb_kwargs:
+            try:
+                opts.cb_kwargs = json.loads(opts.cb_kwargs)
+            except ValueError:
+                raise UsageError("Invalid --cb_kwargs value, pass a valid json string to --cb_kwargs. "
+                                 "Example: --cb_kwargs='{\"foo\" : \"bar\"}'", print_help=False)
 
     def run(self, args, opts):
         # parse arguments

tests/test_command_parse.py

@@ -43,6 +43,12 @@ class MySpider(scrapy.Spider):
         else:
             self.logger.debug('It Works!')
 
+    def parse_request_with_cb_kwargs(self, response, foo=None, key=None):
+        if foo == 'bar' and key == 'value':
+            self.logger.debug('It Works!')
+        else:
+            self.logger.debug('It Does Not Work :(')
+
     def parse_request_without_meta(self, response):
         foo = response.meta.get('foo', 'bar')
 
@@ -120,6 +126,14 @@ ITEM_PIPELINES = {'%s.pipelines.MyPipeline': 1}
                                            self.url('/html')])
         self.assertIn("DEBUG: It Works!", _textmode(stderr))
 
+    @defer.inlineCallbacks
+    def test_request_with_cb_kwargs(self):
+        raw_json_string = '{"foo" : "bar", "key": "value"}'
+        _, _, stderr = yield self.execute(['--spider', self.spider_name,
+                                           '--cb_kwargs', raw_json_string,
+                                           '-c', 'parse_request_with_cb_kwargs',
+                                           self.url('/html')])
+        self.assertIn("DEBUG: It Works!", _textmode(stderr))
 
     @defer.inlineCallbacks
     def test_request_without_meta(self):