Possible to replace Scrapy's default lxml parser with Beautiful Soup's html5lib parser?

Question

Question: Is there a way to integrate BeautifulSoup's html5lib parser into a scrapy project--instead of the scrapy's default lxml parser?
Scrapy's parser fails (for some elements) of my scrape pages.
This only happens every 2 out of 20 pages.

As a fix, I've added BeautifulSoup's parser to the project (which works).
That said, I feel like I'm doubling the work with conditionals and multiple parsers...at a certain point, what's the reason for using Scrapy's parser?
The code does work....it feels like a hack.
I'm no expert--is there a more elegant way to do this?

Much appreciation in advance

Update:
Adding a middleware class to scrapy (from the python package scrapy-beautifulsoup) works like a charm. Apparently, lxml from Scrapy is not as robust as BeautifulSoup's lxml. I didn't have to resort to the html5lib parser--which is 30X+ slower.

class BeautifulSoupMiddleware(object):
    def __init__(self, crawler):
        super(BeautifulSoupMiddleware, self).__init__()

        self.parser = crawler.settings.get('BEAUTIFULSOUP_PARSER', "html.parser")

    @classmethod
    def from_crawler(cls, crawler):
        return cls(crawler)

    def process_response(self, request, response, spider):
        """Overridden process_response would "pipe" response.body through BeautifulSoup."""
        return response.replace(body=str(BeautifulSoup(response.body, self.parser)))

Original:

import scrapy
from scrapy.item import Item, Field
from scrapy.loader.processors import TakeFirst, MapCompose
from scrapy import Selector
from scrapy.loader import ItemLoader
from w3lib.html import remove_tags
from bs4 import BeautifulSoup


class SimpleSpider(scrapy.Spider):
    name = 'SimpleSpider'
    allowed_domains = ['totally-above-board.com']
    start_urls = [
        'https://totally-above-board.com/nefarious-scrape-page.html'
    ]

    custom_settings = {
        'ITEM_PIPELINES': {
            'crawler.spiders.simple_spider.Pipeline': 400
        }
    }

    def parse(self, response):
        yield from self.parse_company_info(response)
        yield from self.parse_reviews(response)

    def parse_company_info(self, response):
        print('parse_company_info')
        print('==================')

        loader = ItemLoader(CompanyItem(), response=response)
        loader.add_xpath('company_name',
                         '//h1[contains(@class,"sp-company-name")]//span//text()')

        yield loader.load_item()

    def parse_reviews(self, response):
        print('parse_reviews')
        print('=============')

        # Beautiful Soup
        selector = Selector(response)

        # On the Page (Total Reviews) # 49
        search = '//span[contains(@itemprop,"reviewCount")]//text()'
        review_count = selector.xpath(search).get()
        review_count = int(float(review_count))

        # Number of elements Scrapy's LXML Could find # 0
        search = '//div[@itemprop ="review"]'
        review_element_count =   len(selector.xpath(search))

        # Use Scrapy or Beautiful Soup?
        if review_count > review_element_count:

            # Try Beautiful Soup
            soup = BeautifulSoup(response.text, "lxml")
            root = soup.findAll("div", {"itemprop": "review"})
            for review in root:
                loader = ItemLoader(ReviewItem(), selector=review)
                review_text = review.find("span", {"itemprop": "reviewBody"}).text
                loader.add_value('review_text', review_text)
                author = review.find("span", {"itemprop": "author"}).text
                loader.add_value('author', author)

                yield loader.load_item()
        else:
            # Try Scrapy 
            review_list_xpath = '//div[@itemprop ="review"]'
            selector = Selector(response)
            for review in selector.xpath(review_list_xpath):
                loader = ItemLoader(ReviewItem(), selector=review)
                loader.add_xpath('review_text',
                                 './/span[@itemprop="reviewBody"]//text()')

                loader.add_xpath('author',
                                 './/span[@itemprop="author"]//text()')

                yield loader.load_item()

        yield from self.paginate_reviews(response)

    def paginate_reviews(self, response):
        print('paginate_reviews')
        print('================')

        # Try Scrapy
        selector = Selector(response)
        search = '''//span[contains(@class,"item-next")]
                    //a[@class="next"]/@href
                 '''
        next_reviews_link = selector.xpath(search).get()

        # Try Beautiful Soup
        if next_reviews_link is None:
            soup = BeautifulSoup(response.text, "lxml")
            try:
                next_reviews_link = soup.find("a", {"class": "next"})['href']
            except Exception as e:
                pass


        if next_reviews_link:
            yield response.follow(next_reviews_link, self.parse_reviews)

Answer 1

You can get a charset error using the @Gallaecio's answer, if the original page was not utf-8 encoded, because the response has set to other encoding. So, you must first switch the encoding.

In addition, there may be a problem of character escaping. For example, if the character < is encountered in the text of html, then it must be escaped as <. Otherwise, "lxml" will delete it and the text near it, considering it an erroneous html tag.

"html5lib" escapes characters, but is slow.

response = response.replace(encoding='utf-8', 
          body=str(BeautifulSoup(response.body, 'html5lib')))

"html.parser" is faster, but from_encoding must also be specified (to example 'cp1251').

response = response.replace(encoding='utf-8', 
          body=str(BeautifulSoup(response.body, 'html.parser', from_encoding='cp1251')))

Answer 2

It’s a common feature request for Parsel, Scrapy’s library for XML/HTML scraping.

However, you don’t need to wait for such a feature to be implemented. You can fix the HTML code using BeautifulSoup, and use Parsel on the fixed HTML:

from bs4 import BeautifulSoup

# …

response = response.replace(body=str(BeautifulSoup(response.body, "html5lib")))