475 lines
18 KiB
Python
475 lines
18 KiB
Python
# encoding: utf-8
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"""Use the HTMLParser library to parse HTML files that aren't too bad."""
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from __future__ import annotations
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# Use of this source code is governed by the MIT license.
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__license__ = "MIT"
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__all__ = [
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"HTMLParserTreeBuilder",
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]
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from html.parser import HTMLParser
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from typing import (
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Any,
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Callable,
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cast,
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Dict,
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Iterable,
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List,
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Optional,
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TYPE_CHECKING,
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Tuple,
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Type,
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Union,
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)
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from bs4.element import (
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AttributeDict,
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CData,
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Comment,
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Declaration,
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Doctype,
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ProcessingInstruction,
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)
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from bs4.dammit import EntitySubstitution, UnicodeDammit
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from bs4.builder import (
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DetectsXMLParsedAsHTML,
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HTML,
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HTMLTreeBuilder,
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STRICT,
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)
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from bs4.exceptions import ParserRejectedMarkup
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if TYPE_CHECKING:
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from bs4 import BeautifulSoup
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from bs4.element import NavigableString
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from bs4._typing import (
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_Encoding,
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_Encodings,
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_RawMarkup,
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)
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HTMLPARSER = "html.parser"
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_DuplicateAttributeHandler = Callable[[Dict[str, str], str, str], None]
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class BeautifulSoupHTMLParser(HTMLParser, DetectsXMLParsedAsHTML):
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#: Constant to handle duplicate attributes by ignoring later values
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#: and keeping the earlier ones.
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REPLACE: str = "replace"
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#: Constant to handle duplicate attributes by replacing earlier values
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#: with later ones.
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IGNORE: str = "ignore"
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"""A subclass of the Python standard library's HTMLParser class, which
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listens for HTMLParser events and translates them into calls
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to Beautiful Soup's tree construction API.
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:param on_duplicate_attribute: A strategy for what to do if a
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tag includes the same attribute more than once. Accepted
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values are: REPLACE (replace earlier values with later
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ones, the default), IGNORE (keep the earliest value
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encountered), or a callable. A callable must take three
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arguments: the dictionary of attributes already processed,
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the name of the duplicate attribute, and the most recent value
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encountered.
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"""
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def __init__(
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self,
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soup: BeautifulSoup,
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*args: Any,
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on_duplicate_attribute: Union[str, _DuplicateAttributeHandler] = REPLACE,
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**kwargs: Any,
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):
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self.soup = soup
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self.on_duplicate_attribute = on_duplicate_attribute
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self.attribute_dict_class = soup.builder.attribute_dict_class
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HTMLParser.__init__(self, *args, **kwargs)
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# Keep a list of empty-element tags that were encountered
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# without an explicit closing tag. If we encounter a closing tag
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# of this type, we'll associate it with one of those entries.
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#
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# This isn't a stack because we don't care about the
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# order. It's a list of closing tags we've already handled and
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# will ignore, assuming they ever show up.
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self.already_closed_empty_element = []
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self._initialize_xml_detector()
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on_duplicate_attribute: Union[str, _DuplicateAttributeHandler]
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already_closed_empty_element: List[str]
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soup: BeautifulSoup
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def error(self, message: str) -> None:
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# NOTE: This method is required so long as Python 3.9 is
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# supported. The corresponding code is removed from HTMLParser
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# in 3.5, but not removed from ParserBase until 3.10.
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# https://github.com/python/cpython/issues/76025
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#
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# The original implementation turned the error into a warning,
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# but in every case I discovered, this made HTMLParser
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# immediately crash with an error message that was less
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# helpful than the warning. The new implementation makes it
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# more clear that html.parser just can't parse this
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# markup. The 3.10 implementation does the same, though it
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# raises AssertionError rather than calling a method. (We
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# catch this error and wrap it in a ParserRejectedMarkup.)
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raise ParserRejectedMarkup(message)
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def handle_startendtag(
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self, name: str, attrs: List[Tuple[str, Optional[str]]]
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) -> None:
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"""Handle an incoming empty-element tag.
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html.parser only calls this method when the markup looks like
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<tag/>.
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"""
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# `handle_empty_element` tells handle_starttag not to close the tag
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# just because its name matches a known empty-element tag. We
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# know that this is an empty-element tag, and we want to call
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# handle_endtag ourselves.
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self.handle_starttag(name, attrs, handle_empty_element=False)
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self.handle_endtag(name)
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def handle_starttag(
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self,
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name: str,
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attrs: List[Tuple[str, Optional[str]]],
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handle_empty_element: bool = True,
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) -> None:
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"""Handle an opening tag, e.g. '<tag>'
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:param handle_empty_element: True if this tag is known to be
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an empty-element tag (i.e. there is not expected to be any
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closing tag).
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"""
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# TODO: handle namespaces here?
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attr_dict: AttributeDict = self.attribute_dict_class()
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for key, value in attrs:
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# Change None attribute values to the empty string
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# for consistency with the other tree builders.
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if value is None:
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value = ""
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if key in attr_dict:
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# A single attribute shows up multiple times in this
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# tag. How to handle it depends on the
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# on_duplicate_attribute setting.
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on_dupe = self.on_duplicate_attribute
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if on_dupe == self.IGNORE:
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pass
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elif on_dupe in (None, self.REPLACE):
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attr_dict[key] = value
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else:
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on_dupe = cast(_DuplicateAttributeHandler, on_dupe)
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on_dupe(attr_dict, key, value)
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else:
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attr_dict[key] = value
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# print("START", name)
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sourceline: Optional[int]
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sourcepos: Optional[int]
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if self.soup.builder.store_line_numbers:
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sourceline, sourcepos = self.getpos()
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else:
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sourceline = sourcepos = None
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tag = self.soup.handle_starttag(
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name, None, None, attr_dict, sourceline=sourceline, sourcepos=sourcepos
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)
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if tag and tag.is_empty_element and handle_empty_element:
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# Unlike other parsers, html.parser doesn't send separate end tag
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# events for empty-element tags. (It's handled in
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# handle_startendtag, but only if the original markup looked like
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# <tag/>.)
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#
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# So we need to call handle_endtag() ourselves. Since we
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# know the start event is identical to the end event, we
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# don't want handle_endtag() to cross off any previous end
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# events for tags of this name.
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self.handle_endtag(name, check_already_closed=False)
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# But we might encounter an explicit closing tag for this tag
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# later on. If so, we want to ignore it.
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self.already_closed_empty_element.append(name)
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if self._root_tag_name is None:
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self._root_tag_encountered(name)
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def handle_endtag(self, name: str, check_already_closed: bool = True) -> None:
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"""Handle a closing tag, e.g. '</tag>'
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:param name: A tag name.
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:param check_already_closed: True if this tag is expected to
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be the closing portion of an empty-element tag,
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e.g. '<tag></tag>'.
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"""
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# print("END", name)
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if check_already_closed and name in self.already_closed_empty_element:
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# This is a redundant end tag for an empty-element tag.
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# We've already called handle_endtag() for it, so just
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# check it off the list.
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# print("ALREADY CLOSED", name)
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self.already_closed_empty_element.remove(name)
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else:
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self.soup.handle_endtag(name)
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def handle_data(self, data: str) -> None:
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"""Handle some textual data that shows up between tags."""
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self.soup.handle_data(data)
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def handle_charref(self, name: str) -> None:
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"""Handle a numeric character reference by converting it to the
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corresponding Unicode character and treating it as textual
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data.
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:param name: Character number, possibly in hexadecimal.
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"""
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# TODO: This was originally a workaround for a bug in
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# HTMLParser. (http://bugs.python.org/issue13633) The bug has
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# been fixed, but removing this code still makes some
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# Beautiful Soup tests fail. This needs investigation.
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if name.startswith("x"):
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real_name = int(name.lstrip("x"), 16)
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elif name.startswith("X"):
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real_name = int(name.lstrip("X"), 16)
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else:
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real_name = int(name)
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data = None
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if real_name < 256:
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# HTML numeric entities are supposed to reference Unicode
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# code points, but sometimes they reference code points in
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# some other encoding (ahem, Windows-1252). E.g. “
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# instead of É for LEFT DOUBLE QUOTATION MARK. This
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# code tries to detect this situation and compensate.
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for encoding in (self.soup.original_encoding, "windows-1252"):
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if not encoding:
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continue
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try:
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data = bytearray([real_name]).decode(encoding)
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except UnicodeDecodeError:
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pass
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if not data:
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try:
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data = chr(real_name)
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except (ValueError, OverflowError):
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pass
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data = data or "\N{REPLACEMENT CHARACTER}"
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self.handle_data(data)
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def handle_entityref(self, name: str) -> None:
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"""Handle a named entity reference by converting it to the
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corresponding Unicode character(s) and treating it as textual
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data.
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:param name: Name of the entity reference.
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"""
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character = EntitySubstitution.HTML_ENTITY_TO_CHARACTER.get(name)
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if character is not None:
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data = character
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else:
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# If this were XML, it would be ambiguous whether "&foo"
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# was an character entity reference with a missing
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# semicolon or the literal string "&foo". Since this is
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# HTML, we have a complete list of all character entity references,
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# and this one wasn't found, so assume it's the literal string "&foo".
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data = "&%s" % name
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self.handle_data(data)
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def handle_comment(self, data: str) -> None:
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"""Handle an HTML comment.
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:param data: The text of the comment.
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"""
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self.soup.endData()
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self.soup.handle_data(data)
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self.soup.endData(Comment)
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def handle_decl(self, data: str) -> None:
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"""Handle a DOCTYPE declaration.
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:param data: The text of the declaration.
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"""
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self.soup.endData()
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data = data[len("DOCTYPE ") :]
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self.soup.handle_data(data)
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self.soup.endData(Doctype)
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def unknown_decl(self, data: str) -> None:
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"""Handle a declaration of unknown type -- probably a CDATA block.
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:param data: The text of the declaration.
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"""
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cls: Type[NavigableString]
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if data.upper().startswith("CDATA["):
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cls = CData
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data = data[len("CDATA[") :]
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else:
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cls = Declaration
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self.soup.endData()
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self.soup.handle_data(data)
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self.soup.endData(cls)
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def handle_pi(self, data: str) -> None:
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"""Handle a processing instruction.
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:param data: The text of the instruction.
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"""
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self.soup.endData()
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self.soup.handle_data(data)
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self._document_might_be_xml(data)
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self.soup.endData(ProcessingInstruction)
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class HTMLParserTreeBuilder(HTMLTreeBuilder):
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"""A Beautiful soup `bs4.builder.TreeBuilder` that uses the
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:py:class:`html.parser.HTMLParser` parser, found in the Python
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standard library.
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"""
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is_xml: bool = False
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picklable: bool = True
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NAME: str = HTMLPARSER
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features: Iterable[str] = [NAME, HTML, STRICT]
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parser_args: Tuple[Iterable[Any], Dict[str, Any]]
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#: The html.parser knows which line number and position in the
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#: original file is the source of an element.
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TRACKS_LINE_NUMBERS: bool = True
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def __init__(
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self,
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parser_args: Optional[Iterable[Any]] = None,
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parser_kwargs: Optional[Dict[str, Any]] = None,
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**kwargs: Any,
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):
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"""Constructor.
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:param parser_args: Positional arguments to pass into
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the BeautifulSoupHTMLParser constructor, once it's
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invoked.
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:param parser_kwargs: Keyword arguments to pass into
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the BeautifulSoupHTMLParser constructor, once it's
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invoked.
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:param kwargs: Keyword arguments for the superclass constructor.
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"""
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# Some keyword arguments will be pulled out of kwargs and placed
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# into parser_kwargs.
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extra_parser_kwargs = dict()
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for arg in ("on_duplicate_attribute",):
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if arg in kwargs:
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value = kwargs.pop(arg)
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extra_parser_kwargs[arg] = value
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super(HTMLParserTreeBuilder, self).__init__(**kwargs)
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parser_args = parser_args or []
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parser_kwargs = parser_kwargs or {}
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parser_kwargs.update(extra_parser_kwargs)
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parser_kwargs["convert_charrefs"] = False
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self.parser_args = (parser_args, parser_kwargs)
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def prepare_markup(
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self,
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markup: _RawMarkup,
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user_specified_encoding: Optional[_Encoding] = None,
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document_declared_encoding: Optional[_Encoding] = None,
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exclude_encodings: Optional[_Encodings] = None,
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) -> Iterable[Tuple[str, Optional[_Encoding], Optional[_Encoding], bool]]:
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"""Run any preliminary steps necessary to make incoming markup
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acceptable to the parser.
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:param markup: Some markup -- probably a bytestring.
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:param user_specified_encoding: The user asked to try this encoding.
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:param document_declared_encoding: The markup itself claims to be
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in this encoding.
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:param exclude_encodings: The user asked _not_ to try any of
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these encodings.
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:yield: A series of 4-tuples: (markup, encoding, declared encoding,
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has undergone character replacement)
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Each 4-tuple represents a strategy for parsing the document.
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This TreeBuilder uses Unicode, Dammit to convert the markup
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into Unicode, so the ``markup`` element of the tuple will
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always be a string.
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"""
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if isinstance(markup, str):
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# Parse Unicode as-is.
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yield (markup, None, None, False)
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return
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# Ask UnicodeDammit to sniff the most likely encoding.
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known_definite_encodings: List[_Encoding] = []
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if user_specified_encoding:
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# This was provided by the end-user; treat it as a known
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# definite encoding per the algorithm laid out in the
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# HTML5 spec. (See the EncodingDetector class for
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# details.)
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known_definite_encodings.append(user_specified_encoding)
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user_encodings: List[_Encoding] = []
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if document_declared_encoding:
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# This was found in the document; treat it as a slightly
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# lower-priority user encoding.
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user_encodings.append(document_declared_encoding)
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dammit = UnicodeDammit(
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markup,
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known_definite_encodings=known_definite_encodings,
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user_encodings=user_encodings,
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is_html=True,
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exclude_encodings=exclude_encodings,
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)
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if dammit.unicode_markup is None:
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# In every case I've seen, Unicode, Dammit is able to
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# convert the markup into Unicode, even if it needs to use
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# REPLACEMENT CHARACTER. But there is a code path that
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# could result in unicode_markup being None, and
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# HTMLParser can only parse Unicode, so here we handle
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# that code path.
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raise ParserRejectedMarkup(
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"Could not convert input to Unicode, and html.parser will not accept bytestrings."
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)
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else:
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yield (
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dammit.unicode_markup,
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dammit.original_encoding,
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dammit.declared_html_encoding,
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dammit.contains_replacement_characters,
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)
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def feed(self, markup: _RawMarkup) -> None:
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args, kwargs = self.parser_args
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# HTMLParser.feed will only handle str, but
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# BeautifulSoup.markup is allowed to be _RawMarkup, because
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# it's set by the yield value of
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# TreeBuilder.prepare_markup. Fortunately,
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# HTMLParserTreeBuilder.prepare_markup always yields a str
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# (UnicodeDammit.unicode_markup).
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assert isinstance(markup, str)
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# We know BeautifulSoup calls TreeBuilder.initialize_soup
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# before calling feed(), so we can assume self.soup
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# is set.
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assert self.soup is not None
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parser = BeautifulSoupHTMLParser(self.soup, *args, **kwargs)
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try:
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parser.feed(markup)
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parser.close()
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except AssertionError as e:
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# html.parser raises AssertionError in rare cases to
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# indicate a fatal problem with the markup, especially
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# when there's an error in the doctype declaration.
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raise ParserRejectedMarkup(e)
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parser.already_closed_empty_element = []
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