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Merge pull request #4982 from wRAR/refactor-spidermiddlewaremanager
Refactor SpiderMiddlewareManager.scrape_response.
This commit is contained in:
Adrián Chaves
GitHub
commit
de82ca8547
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@ -41,86 +41,92 @@ class SpiderMiddlewareManager(MiddlewareManager):
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process_spider_exception = getattr(mw, 'process_spider_exception', None)
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self.methods['process_spider_exception'].appendleft(process_spider_exception)
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def scrape_response(self, scrape_func, response, request, spider):
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def process_spider_input(response):
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for method in self.methods['process_spider_input']:
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try:
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result = method(response=response, spider=spider)
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if result is not None:
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msg = (f"Middleware {_fname(method)} must return None "
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f"or raise an exception, got {type(result)}")
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raise _InvalidOutput(msg)
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except _InvalidOutput:
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raise
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except Exception:
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return scrape_func(Failure(), request, spider)
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return scrape_func(response, request, spider)
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def _evaluate_iterable(iterable, exception_processor_index, recover_to):
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def _process_spider_input(self, scrape_func, response, request, spider):
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for method in self.methods['process_spider_input']:
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try:
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for r in iterable:
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yield r
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result = method(response=response, spider=spider)
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if result is not None:
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msg = (f"Middleware {_fname(method)} must return None "
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f"or raise an exception, got {type(result)}")
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raise _InvalidOutput(msg)
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except _InvalidOutput:
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raise
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except Exception:
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return scrape_func(Failure(), request, spider)
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return scrape_func(response, request, spider)
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def _evaluate_iterable(self, response, spider, iterable, exception_processor_index, recover_to):
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try:
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for r in iterable:
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yield r
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except Exception as ex:
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exception_result = self._process_spider_exception(response, spider, Failure(ex),
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exception_processor_index)
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if isinstance(exception_result, Failure):
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raise
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recover_to.extend(exception_result)
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def _process_spider_exception(self, response, spider, _failure, start_index=0):
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exception = _failure.value
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# don't handle _InvalidOutput exception
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if isinstance(exception, _InvalidOutput):
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return _failure
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method_list = islice(self.methods['process_spider_exception'], start_index, None)
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for method_index, method in enumerate(method_list, start=start_index):
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if method is None:
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continue
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result = method(response=response, exception=exception, spider=spider)
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if _isiterable(result):
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# stop exception handling by handing control over to the
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# process_spider_output chain if an iterable has been returned
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return self._process_spider_output(response, spider, result, method_index + 1)
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elif result is None:
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continue
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else:
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msg = (f"Middleware {_fname(method)} must return None "
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f"or an iterable, got {type(result)}")
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raise _InvalidOutput(msg)
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return _failure
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def _process_spider_output(self, response, spider, result, start_index=0):
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# items in this iterable do not need to go through the process_spider_output
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# chain, they went through it already from the process_spider_exception method
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recovered = MutableChain()
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method_list = islice(self.methods['process_spider_output'], start_index, None)
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for method_index, method in enumerate(method_list, start=start_index):
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if method is None:
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continue
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try:
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# might fail directly if the output value is not a generator
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result = method(response=response, result=result, spider=spider)
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except Exception as ex:
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exception_result = process_spider_exception(Failure(ex), exception_processor_index)
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exception_result = self._process_spider_exception(response, spider, Failure(ex), method_index + 1)
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if isinstance(exception_result, Failure):
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raise
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recover_to.extend(exception_result)
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return exception_result
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if _isiterable(result):
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result = self._evaluate_iterable(response, spider, result, method_index + 1, recovered)
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else:
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msg = (f"Middleware {_fname(method)} must return an "
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f"iterable, got {type(result)}")
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raise _InvalidOutput(msg)
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def process_spider_exception(_failure, start_index=0):
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exception = _failure.value
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# don't handle _InvalidOutput exception
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if isinstance(exception, _InvalidOutput):
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return _failure
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method_list = islice(self.methods['process_spider_exception'], start_index, None)
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for method_index, method in enumerate(method_list, start=start_index):
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if method is None:
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continue
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result = method(response=response, exception=exception, spider=spider)
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if _isiterable(result):
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# stop exception handling by handing control over to the
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# process_spider_output chain if an iterable has been returned
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return process_spider_output(result, method_index + 1)
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elif result is None:
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continue
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else:
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msg = (f"Middleware {_fname(method)} must return None "
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f"or an iterable, got {type(result)}")
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raise _InvalidOutput(msg)
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return _failure
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return MutableChain(result, recovered)
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def process_spider_output(result, start_index=0):
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# items in this iterable do not need to go through the process_spider_output
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# chain, they went through it already from the process_spider_exception method
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recovered = MutableChain()
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method_list = islice(self.methods['process_spider_output'], start_index, None)
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for method_index, method in enumerate(method_list, start=start_index):
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if method is None:
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continue
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try:
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# might fail directly if the output value is not a generator
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result = method(response=response, result=result, spider=spider)
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except Exception as ex:
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exception_result = process_spider_exception(Failure(ex), method_index + 1)
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if isinstance(exception_result, Failure):
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raise
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return exception_result
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if _isiterable(result):
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result = _evaluate_iterable(result, method_index + 1, recovered)
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else:
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msg = (f"Middleware {_fname(method)} must return an "
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f"iterable, got {type(result)}")
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raise _InvalidOutput(msg)
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return MutableChain(result, recovered)
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def _process_callback_output(self, response, spider, result):
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recovered = MutableChain()
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result = self._evaluate_iterable(response, spider, result, 0, recovered)
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return MutableChain(self._process_spider_output(response, spider, result), recovered)
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def scrape_response(self, scrape_func, response, request, spider):
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def process_callback_output(result):
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recovered = MutableChain()
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result = _evaluate_iterable(result, 0, recovered)
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return MutableChain(process_spider_output(result), recovered)
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return self._process_callback_output(response, spider, result)
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dfd = mustbe_deferred(process_spider_input, response)
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def process_spider_exception(_failure):
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return self._process_spider_exception(response, spider, _failure)
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dfd = mustbe_deferred(self._process_spider_input, scrape_func, response, request, spider)
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dfd.addCallbacks(callback=process_callback_output, errback=process_spider_exception)
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return dfd
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