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Allow spiders to also return/yield ItemLoader. #3244

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Allow spiders to also return/yield ItemLoader. #3244

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04db8cb
Allow spiders to also return/yield ItemLoader.
vincent-ferotin May 3, 2018
e0a615a
Merge branch 'master' into feature-allow-yielding-loader
vincent-ferotin May 18, 2018
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9 changes: 9 additions & 0 deletions docs/topics/loaders.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,15 @@ called which actually returns the item populated with the data
previously extracted and collected with the :meth:`~ItemLoader.add_xpath`,
:meth:`~ItemLoader.add_css`, and :meth:`~ItemLoader.add_value` calls.

Note that it is also possible for the spider to return/yield the loader it-self,
letting Scrapy calling the :meth:`ItemLoader.load_item` behind::

def parse(self, response):
loader = ItemLoader(item=Product(), response=response)
# (...)
return loader


.. _topics-loaders-processors:

Input and Output processors
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12 changes: 9 additions & 3 deletions scrapy/core/scraper.py
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Expand Up @@ -15,6 +15,7 @@
from scrapy import signals
from scrapy.http import Request, Response
from scrapy.item import BaseItem
from scrapy.loader import ItemLoader
from scrapy.core.spidermw import SpiderMiddlewareManager
from scrapy.utils.request import referer_str

Expand Down Expand Up @@ -176,9 +177,13 @@ def handle_spider_output(self, result, request, response, spider):
return dfd

def _process_spidermw_output(self, output, request, response, spider):
"""Process each Request/Item (given in the output parameter) returned
from the given spider
"""Process each Request/Item/ItemLoader (given in the output parameter)
returned from the given spider
"""
# Allow ItemLoader to be returned: convert it to new Item
if isinstance(output, ItemLoader):
output = output.load_item()

if isinstance(output, Request):
self.crawler.engine.crawl(request=output, spider=spider)
elif isinstance(output, (BaseItem, dict)):
Expand All @@ -190,7 +195,8 @@ def _process_spidermw_output(self, output, request, response, spider):
pass
else:
typename = type(output).__name__
logger.error('Spider must return Request, BaseItem, dict or None, '
logger.error('Spider must return Request, BaseItem, ItemLoader, '
'dict or None, '
'got %(typename)r in %(request)s',
{'request': request, 'typename': typename},
extra={'spider': spider})
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