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import json
from itemadapter import is_item, ItemAdapter
from scrapy.contracts import Contract
from scrapy.exceptions import ContractFail
from scrapy.http import Request
# contracts
class UrlContract(Contract):
""" Contract to set the url of the request (mandatory)
@url http://scrapy.org
"""
name = 'url'
def adjust_request_args(self, args):
args['url'] = self.args[0]
return args
class CallbackKeywordArgumentsContract(Contract):
""" Contract to set the keyword arguments for the request.
The value should be a JSON-encoded dictionary, e.g.:
@cb_kwargs {"arg1": "some value"}
"""
name = 'cb_kwargs'
def adjust_request_args(self, args):
args['cb_kwargs'] = json.loads(' '.join(self.args))
return args
class ReturnsContract(Contract):
""" Contract to check the output of a callback
general form:
@returns request(s)/item(s) [min=1 [max]]
e.g.:
@returns request
@returns request 2
@returns request 2 10
@returns request 0 10
"""
name = 'returns'
object_type_verifiers = {
'request': lambda x: isinstance(x, Request),
'requests': lambda x: isinstance(x, Request),
'item': is_item,
'items': is_item,
}
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
if len(self.args) not in [1, 2, 3]:
raise ValueError(
f"Incorrect argument quantity: expected 1, 2 or 3, got {len(self.args)}"
)
self.obj_name = self.args[0] or None
self.obj_type_verifier = self.object_type_verifiers[self.obj_name]
try:
self.min_bound = int(self.args[1])
except IndexError:
self.min_bound = 1
try:
self.max_bound = int(self.args[2])
except IndexError:
self.max_bound = float('inf')
def post_process(self, output):
occurrences = 0
for x in output:
if self.obj_type_verifier(x):
occurrences += 1
assertion = (self.min_bound <= occurrences <= self.max_bound)
if not assertion:
if self.min_bound == self.max_bound:
expected = self.min_bound
else:
expected = f'{self.min_bound}..{self.max_bound}'
raise ContractFail(f"Returned {occurrences} {self.obj_name}, expected {expected}")
class ScrapesContract(Contract):
""" Contract to check presence of fields in scraped items
@scrapes page_name page_body
"""
name = 'scrapes'
def post_process(self, output):
for x in output:
if is_item(x):
missing = [arg for arg in self.args if arg not in ItemAdapter(x)]
if missing:
missing_fields = ", ".join(missing)
raise ContractFail(f"Missing fields: {missing_fields}")
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