# pylint:disable-msg=E0611,I1101
"""
Module bundling functions related to HTML and text processing,
content filtering and language detection.
"""
try:
import gzip
HAS_GZIP = True
except ImportError:
HAS_GZIP = False
import logging
import re
try:
import zlib
HAS_ZLIB = True
except ImportError:
HAS_ZLIB = False
from functools import lru_cache
from itertools import islice
from typing import Any, cast, List, Literal, Optional, Tuple, Union
from unicodedata import normalize
# response compression
try:
import brotli # type: ignore
HAS_BROTLI = True
except ImportError:
HAS_BROTLI = False
try:
import zstandard
HAS_ZSTD = True
except ImportError:
HAS_ZSTD = False
# language detection
try:
import py3langid # type: ignore
LANGID_FLAG = True
except ImportError:
LANGID_FLAG = False
# CChardet is faster and can be more accurate
try:
from cchardet import detect as cchardet_detect # type: ignore
except ImportError:
cchardet_detect = None
from charset_normalizer import from_bytes
from lxml.etree import _Element
from lxml.html import HtmlElement, HTMLParser, fromstring
# response types
from urllib3.response import HTTPResponse
LOGGER = logging.getLogger(__name__)
UNICODE_ALIASES = {'utf-8', 'utf_8'}
DOCTYPE_TAG = re.compile("^< ?! ?DOCTYPE[^>]*/[^<]*>", re.I)
FAULTY_HTML = re.compile(r"(<html.*?)\s*/>", re.I)
HTML_STRIP_TAGS = re.compile(r'(<!--.*?-->|<[^>]*>)')
# control characters
INVALID_XML_CHARS = re.compile(r'[\x00-\x08\x0b\x0c\x0e-\x1f\ufffe\uffff]')
# note: htmldate could use HTML comments
# huge_tree=True, remove_blank_text=True
HTML_PARSER = HTMLParser(collect_ids=False, default_doctype=False, encoding='utf-8', remove_comments=True, remove_pis=True)
LINES_TRIMMING = re.compile(r'(?<![p{P}>])\n', flags=re.UNICODE|re.MULTILINE)
URL_BLACKLIST_REGEX = re.compile(r'^https?://|/+$')
# Regex to check image file extensions
IMAGE_EXTENSION = re.compile(r'[^\s]+\.(avif|bmp|gif|hei[cf]|jpe?g|png|webp)(\b|$)')
FORMATTING_PROTECTED = {'cell', 'head', 'hi', 'item', 'p', 'quote', 'ref', 'td'}
SPACING_PROTECTED = {'code', 'pre'}
# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Language
TARGET_LANG_ATTRS = ('http-equiv="content-language"', 'property="og:locale"')
RE_HTML_LANG = re.compile(r'([a-z]{2})')
# Mostly filters for social media
RE_FILTER = re.compile(r'\W*(Drucken|E-?Mail|Facebook|Flipboard|Google|Instagram|'
'Linkedin|Mail|PDF|Pinterest|Pocket|Print|QQ|Reddit|Twitter|'
'WeChat|WeiBo|Whatsapp|Xing|Mehr zum Thema:?|More on this.{,8}$)$',
flags=re.IGNORECASE)
# COMMENTS_BLACKLIST = ('( Abmelden / Ändern )') # Fill in your details below|Trage deine Daten unten|Kommentar verfassen|Bitte logge dich|Hinterlasse einen Kommentar| to %s| mit %s)
def handle_compressed_file(filecontent: bytes) -> bytes:
"""
Don't trust response headers and try to decompress a binary string
with a cascade of installed packages. Use magic numbers when available.
"""
if not isinstance(filecontent, bytes):
return filecontent
# source: https://stackoverflow.com/questions/3703276/how-to-tell-if-a-file-is-gzip-compressed
if HAS_GZIP and filecontent[:3] == b"\x1f\x8b\x08":
try:
return gzip.decompress(filecontent)
except Exception: # EOFError, OSError, gzip.BadGzipFile
LOGGER.warning("invalid GZ file")
# try zstandard
if HAS_ZSTD and filecontent[:4] == b"\x28\xb5\x2f\xfd":
try:
return zstandard.decompress(filecontent) # max_output_size=???
except zstandard.ZstdError:
LOGGER.warning("invalid ZSTD file")
# try brotli
if HAS_BROTLI:
try:
return brotli.decompress(filecontent)
except brotli.error:
pass # logging.debug('invalid Brotli file')
# try zlib/deflate
if HAS_ZLIB:
try:
return zlib.decompress(filecontent)
except zlib.error:
pass
# return content unchanged if decompression failed
return filecontent
def isutf8(data: bytes) -> bool:
"""Simple heuristic to determine if a bytestring uses standard unicode encoding"""
try:
data.decode('UTF-8')
except UnicodeDecodeError:
return False
return True
def detect_encoding(bytesobject: bytes) -> List[str]:
""""Read all input or first chunk and return a list of encodings"""
# alternatives: https://github.com/scrapy/w3lib/blob/master/w3lib/encoding.py
# unicode-test
if isutf8(bytesobject):
return ['utf-8']
guesses = []
# additional module
if cchardet_detect is not None:
cchardet_guess = cchardet_detect(bytesobject)['encoding']
if cchardet_guess is not None:
guesses.append(cchardet_guess.lower())
# try charset_normalizer on first part, fallback on full document
if len(bytesobject) < 10000:
detection_results = from_bytes(bytesobject)
else:
detection_results = from_bytes(bytesobject[:5000] + bytesobject[-5000:]) or \
from_bytes(bytesobject)
# return alternatives
if len(detection_results) > 0:
guesses.extend([r.encoding for r in detection_results])
# it cannot be utf-8 (tested above)
return [g for g in guesses if g not in UNICODE_ALIASES]
[docs]
def decode_file(filecontent: Union[bytes, str]) -> str:
"""Check if the bytestring could be GZip and eventually decompress it,
guess bytestring encoding and try to decode to Unicode string.
Resort to destructive conversion otherwise."""
if isinstance(filecontent, str):
return filecontent
htmltext = None
# GZip and Brotli test
filecontent = handle_compressed_file(filecontent)
# encoding
for guessed_encoding in detect_encoding(filecontent):
try:
htmltext = filecontent.decode(guessed_encoding)
except (LookupError, UnicodeDecodeError): # VISCII: lookup
LOGGER.warning('wrong encoding detected: %s', guessed_encoding)
htmltext = None
else:
break
# return original content if nothing else succeeded
return htmltext or str(filecontent, encoding='utf-8', errors='replace')
def is_dubious_html(beginning: str) -> bool:
"Assess if the object is proper HTML (awith a corresponding tag or declaration)."
return "html" not in beginning
def repair_faulty_html(htmlstring: str, beginning: str) -> str:
"Repair faulty HTML strings to make then palatable for libxml2."
htmlstring = INVALID_XML_CHARS.sub("", htmlstring)
# libxml2/LXML issue: https://bugs.launchpad.net/lxml/+bug/1955915
if "doctype" in beginning:
firstline, _, rest = htmlstring.partition("\n")
htmlstring = DOCTYPE_TAG.sub("", firstline, count=1) + "\n" + rest
# other issue with malformed documents: check first three lines
for i, line in enumerate(iter(htmlstring.splitlines())):
if "<html" in line and line.endswith("/>"):
htmlstring = FAULTY_HTML.sub(r"\1>", htmlstring, count=1)
break
if i > 2:
break
return htmlstring
def fromstring_bytes(htmlobject: str) -> Optional[HtmlElement]:
"Try to pass bytes to LXML parser."
tree = None
try:
tree = fromstring(htmlobject.encode("utf8", "surrogatepass"), parser=HTML_PARSER)
except Exception as err:
LOGGER.error("lxml parser bytestring %s", err)
return tree
[docs]
def load_html(htmlobject: Any) -> Optional[HtmlElement]:
"""Load object given as input and validate its type
(accepted: lxml.html tree, trafilatura/urllib3 response, bytestring and string)
"""
# use tree directly
if isinstance(htmlobject, HtmlElement):
return htmlobject
# use trafilatura or urllib3 responses directly
if isinstance(htmlobject, HTTPResponse) or hasattr(htmlobject, "data"):
htmlobject = htmlobject.data
# do not accept any other type after this point
if not isinstance(htmlobject, (bytes, str)):
raise TypeError("incompatible input type", type(htmlobject))
# start processing
tree = None
# try to guess encoding and decode file: if None then keep original
htmlobject = decode_file(htmlobject)
# sanity checks
beginning = htmlobject[:50].lower()
check_flag = is_dubious_html(beginning)
# repair first
htmlobject = repair_faulty_html(htmlobject, beginning)
# first pass: use Unicode string
fallback_parse = False
try:
tree = fromstring(htmlobject, parser=HTML_PARSER)
except ValueError:
# "Unicode strings with encoding declaration are not supported."
tree = fromstring_bytes(htmlobject)
fallback_parse = True
except Exception as err: # pragma: no cover
LOGGER.error("lxml parsing failed: %s", err)
# second pass: try passing bytes to LXML
if (tree is None or len(tree) < 1) and not fallback_parse:
tree = fromstring_bytes(htmlobject)
# rejection test: is it (well-formed) HTML at all?
# log parsing errors
if tree is not None and check_flag is True and len(tree) < 2:
LOGGER.error(
"parsed tree length: %s, wrong data type or not valid HTML", len(tree)
)
tree = None
return tree
@lru_cache(maxsize=2**14) # sys.maxunicode = 1114111
def return_printables_and_spaces(char: str) -> str:
'Return a character if it belongs to certain classes'
return char if char.isprintable() or char.isspace() else ''
def remove_control_characters(string: str) -> str:
'''Prevent non-printable and XML invalid character errors'''
# in case most strings are already clean
if string.isprintable():
return string
return ''.join(map(return_printables_and_spaces, string))
def normalize_unicode(string: str, unicodeform: Literal['NFC', 'NFD', 'NFKC', 'NFKD'] = 'NFC') -> str:
'Normalize the given string to the specified unicode format.'
return normalize(unicodeform, string)
@lru_cache(maxsize=1024)
def line_processing(line: str, preserve_space: bool = False, trailing_space: bool = False) -> Optional[str]:
'''Remove HTML space entities, then discard incompatible unicode
and invalid XML characters on line level'''
# spacing HTML entities: https://www.w3.org/MarkUp/html-spec/html-spec_13.html
# unique code spaces
new_line = remove_control_characters(line.replace(' ', '\r').replace(' ', '\n').replace(' ', '\u00A0'))
if not preserve_space:
# remove newlines that are not related to punctuation or markup
# remove non-printable chars and normalize space characters (including Unicode spaces)
new_line = trim(LINES_TRIMMING.sub(r" ", new_line))
# prune empty lines
if all(map(str.isspace, new_line)):
new_line = None # type: ignore[assignment]
elif trailing_space:
space_before = " " if line[0].isspace() else ""
space_after = " " if line[-1].isspace() else ""
new_line = "".join([space_before, new_line, space_after])
return new_line
[docs]
def sanitize(text: str, preserve_space: bool = False, trailing_space: bool = False) -> Optional[str]:
'''Convert text and discard incompatible and invalid characters'''
# consider all text as a single line
if trailing_space:
return line_processing(text, preserve_space, True)
# process line by line
try:
return '\n'.join(filter(None, (line_processing(l, preserve_space) for l in text.splitlines()))).replace('\u2424', '')
except AttributeError:
return None
def sanitize_tree(tree: _Element) -> _Element:
'''Trims spaces, removes control characters and normalizes unicode'''
for elem in tree.iter():
parent = elem.getparent()
parent_tag = parent.tag if parent is not None else ""
# preserve space if the element or its parent is a specific tag, or if the element has text and children
# the last part is relevant for item elements with ref inside for example
preserve_space = elem.tag in SPACING_PROTECTED or parent_tag in SPACING_PROTECTED
trailing_space = elem.tag in FORMATTING_PROTECTED or parent_tag in FORMATTING_PROTECTED or preserve_space
# remove invalid attributes
for attribute in elem.attrib:
if ':' in attribute: # colon is reserved for namespaces in XML
if not elem.attrib[attribute] or attribute.split(':', 1)[0] not in tree.nsmap:
elem.attrib.pop(attribute)
if elem.text:
elem.text = sanitize(elem.text, preserve_space, trailing_space)
if elem.tail:
elem.tail = sanitize(elem.tail, preserve_space, trailing_space)
return tree
[docs]
@lru_cache(maxsize=1024)
def trim(string: str) -> str:
"Remove unnecessary spaces within a text string."
try:
# remove newlines that are not related to punctuation or markup + proper trimming
return " ".join(string.split()).strip()
except (AttributeError, TypeError):
return ""
def is_image_element(element: _Element) -> bool:
'''Check if an element is a valid img element'''
for attr in ("data-src", "src"):
src = element.get(attr, "")
if is_image_file(src):
return True
else:
# take the first corresponding attribute
for attr, value in element.attrib.items():
if attr.startswith("data-src") and is_image_file(value):
return True
return False
def is_image_file(imagesrc: Optional[str]) -> bool:
'''Check if the observed string corresponds to a valid image extension.
Use a length threshold and apply a regex on the content.'''
if imagesrc is None or len(imagesrc) > 8192:
return False
return bool(IMAGE_EXTENSION.search(imagesrc))
def make_chunks(iterable: Any, n: int) -> Any:
"Chunk data into smaller pieces."
# 3.12+: https://docs.python.org/3/library/itertools.html#itertools.batched
iterator = iter(iterable)
while batch := tuple(islice(iterator, n)):
yield batch
def is_acceptable_length(my_len: int, options: Any) -> bool:
"Check if the document length is within acceptable boundaries."
if my_len < options.min_file_size:
LOGGER.error("too small/incorrect for URL %s", options.url)
return False
if my_len > options.max_file_size:
LOGGER.error("too large: length %s for URL %s", my_len, options.url)
return False
return True
def check_html_lang(tree: HtmlElement, target_language: str, strict: bool = False) -> bool:
"""Check HTML meta-elements for language information and split
the result in case there are several languages."""
for attr in TARGET_LANG_ATTRS:
elems = tree.findall(f'.//meta[@{attr}][@content]')
if elems:
if any(target_language in RE_HTML_LANG.split(elem.get("content", "").lower()) for elem in elems):
return True
LOGGER.debug("%s lang attr failed", attr)
return False
# HTML lang attribute: sometimes a wrong indication
if strict:
elems = tree.xpath("//html[@lang]")
if elems:
if any(target_language in RE_HTML_LANG.split(elem.get("lang", "").lower()) for elem in elems):
return True
LOGGER.debug("HTML lang failed")
return False
LOGGER.debug("No relevant lang elements found")
return True
def language_classifier(temp_text: str, temp_comments: str) -> Optional[str]:
'''Run external component (if installed) for language identification'''
if LANGID_FLAG is True:
result, _ = (
py3langid.classify(temp_text)
if len(temp_text) > len(temp_comments)
else py3langid.classify(temp_comments)
)
else: # pragma: no cover
LOGGER.warning('Language detector not installed, skipping detection')
result = None
return result
def language_filter(temp_text: str, temp_comments: str, target_language: str, docmeta: Any) -> Tuple[bool, Any]:
'''Filter text based on language detection and store relevant information'''
# todo: run and pass info along anyway?
if target_language is not None:
# more thorough: detection on actual text content
docmeta.language = language_classifier(temp_text, temp_comments)
# HTML lang check? sometimes contradicted by detection above
#if docmeta.language is None:
# if check_html_lang(tree, target_language) is False:
# LOGGER.error('wrong HTML meta language for URL %s', url)
# raise ValueError
if docmeta.language is not None and docmeta.language != target_language:
LOGGER.warning('wrong language: %s %s', docmeta.language, docmeta.url)
return True, docmeta
return False, docmeta
def textfilter(element: _Element) -> bool:
'''Filter out unwanted text'''
testtext = element.tail if element.text is None else element.text
# to check: line len → continue if len(line) <= 5
return not testtext or testtext.isspace() or any(map(RE_FILTER.match, testtext.splitlines()))
def text_chars_test(string: Optional[str]) -> bool:
'''Determine if a string is only composed of spaces and/or control characters'''
# or not re.search(r'\w', string)
# return string is not None and len(string) != 0 and not string.isspace()
return bool(string) and not string.isspace() # type: ignore[union-attr]
def copy_attributes(dest_elem: _Element, src_elem: _Element) -> None:
'''Copy attributes from src element to dest element'''
for key in src_elem.keys():
dest_elem.set(key, src_elem.attrib[key])
def is_in_table_cell(elem: _Element) -> bool:
'''Check whether an element is in a table cell'''
# return elem.getparent() is not None and bool(elem.xpath('//ancestor::cell'))
if elem.getparent() is None:
return False
current: Optional[_Element] = elem
while current is not None:
if current.tag == 'cell':
return True
current = current.getparent()
return False
def is_last_element_in_cell(elem: _Element) -> bool:
'''Check whether an element is the last element in table cell'''
if not is_in_table_cell(elem): # shortcut
return False
if elem.tag == "cell":
children = elem.getchildren()
return not children or children[-1] == elem
else:
parent = cast(_Element, elem.getparent())
children = parent.getchildren()
return not children or children[-1] == elem
def is_element_in_item(element: _Element) -> bool:
"""Check whether an element is a list item or within a list item"""
current: Optional[_Element] = element
while current is not None:
if current.tag == 'item':
return True
current = current.getparent()
return False
def is_first_element_in_item(element: _Element) -> bool:
"""Check whether an element is the first element in list item"""
if element.tag == 'item' and element.text:
return True
current: Optional[_Element] = element
item_ancestor = None
while current is not None:
if current.tag == 'item':
item_ancestor = current
break
current = current.getparent()
if item_ancestor is None:
return False
elif not item_ancestor.text:
return True
return False
def is_last_element_in_item(element: _Element) -> bool:
"""Check whether an element is the last element in list item"""
if not is_element_in_item(element):
return False
# pure text only in list item
if element.tag == 'item':
return len(element.getchildren()) == 0
# element within list item
next_element = element.getnext()
if next_element is None:
return True
else:
return next_element.tag == 'item'
