python/py313/Lib/site-packages/bs4/builder/_htmlparser.py

# encoding: utf-8
"""Use the HTMLParser library to parse HTML files that aren't too bad."""
from __future__ import annotations

# Use of this source code is governed by the MIT license.
__license__ = "MIT"

__all__ = [
    "HTMLParserTreeBuilder",
]

from html.parser import HTMLParser

from typing import (
    Any,
    Callable,
    cast,
    Dict,
    Iterable,
    List,
    Optional,
    TYPE_CHECKING,
    Tuple,
    Type,
    Union,
)

from bs4.element import (
    AttributeDict,
    CData,
    Comment,
    Declaration,
    Doctype,
    ProcessingInstruction,
)
from bs4.dammit import EntitySubstitution, UnicodeDammit

from bs4.builder import (
    DetectsXMLParsedAsHTML,
    HTML,
    HTMLTreeBuilder,
    STRICT,
)

from bs4.exceptions import ParserRejectedMarkup

if TYPE_CHECKING:
    from bs4 import BeautifulSoup
    from bs4.element import NavigableString
    from bs4._typing import (
        _Encoding,
        _Encodings,
        _RawMarkup,
    )

HTMLPARSER = "html.parser"

_DuplicateAttributeHandler = Callable[[Dict[str, str], str, str], None]


class BeautifulSoupHTMLParser(HTMLParser, DetectsXMLParsedAsHTML):
    #: Constant to handle duplicate attributes by ignoring later values
    #: and keeping the earlier ones.
    REPLACE: str = "replace"

    #: Constant to handle duplicate attributes by replacing earlier values
    #: with later ones.
    IGNORE: str = "ignore"

    """A subclass of the Python standard library's HTMLParser class, which
    listens for HTMLParser events and translates them into calls
    to Beautiful Soup's tree construction API.

        :param on_duplicate_attribute: A strategy for what to do if a
            tag includes the same attribute more than once. Accepted
            values are: REPLACE (replace earlier values with later
            ones, the default), IGNORE (keep the earliest value
            encountered), or a callable. A callable must take three
            arguments: the dictionary of attributes already processed,
            the name of the duplicate attribute, and the most recent value
            encountered.
    """

    def __init__(
        self,
        soup: BeautifulSoup,
        *args: Any,
        on_duplicate_attribute: Union[str, _DuplicateAttributeHandler] = REPLACE,
        **kwargs: Any,
    ):
        self.soup = soup
        self.on_duplicate_attribute = on_duplicate_attribute
        self.attribute_dict_class = soup.builder.attribute_dict_class
        HTMLParser.__init__(self, *args, **kwargs)

        # Keep a list of empty-element tags that were encountered
        # without an explicit closing tag. If we encounter a closing tag
        # of this type, we'll associate it with one of those entries.
        #
        # This isn't a stack because we don't care about the
        # order. It's a list of closing tags we've already handled and
        # will ignore, assuming they ever show up.
        self.already_closed_empty_element = []

        self._initialize_xml_detector()

    on_duplicate_attribute: Union[str, _DuplicateAttributeHandler]
    already_closed_empty_element: List[str]
    soup: BeautifulSoup

    def error(self, message: str) -> None:
        # NOTE: This method is required so long as Python 3.9 is
        # supported. The corresponding code is removed from HTMLParser
        # in 3.5, but not removed from ParserBase until 3.10.
        # https://github.com/python/cpython/issues/76025
        #
        # The original implementation turned the error into a warning,
        # but in every case I discovered, this made HTMLParser
        # immediately crash with an error message that was less
        # helpful than the warning. The new implementation makes it
        # more clear that html.parser just can't parse this
        # markup. The 3.10 implementation does the same, though it
        # raises AssertionError rather than calling a method. (We
        # catch this error and wrap it in a ParserRejectedMarkup.)
        raise ParserRejectedMarkup(message)

    def handle_startendtag(
        self, tag: str, attrs: List[Tuple[str, Optional[str]]]
    ) -> None:
        """Handle an incoming empty-element tag.

        html.parser only calls this method when the markup looks like
        <tag/>.
        """
        # `handle_empty_element` tells handle_starttag not to close the tag
        # just because its name matches a known empty-element tag. We
        # know that this is an empty-element tag, and we want to call
        # handle_endtag ourselves.
        self.handle_starttag(tag, attrs, handle_empty_element=False)
        self.handle_endtag(tag)

    def handle_starttag(
        self,
        tag: str,
        attrs: List[Tuple[str, Optional[str]]],
        handle_empty_element: bool = True,
    ) -> None:
        """Handle an opening tag, e.g. '<tag>'

        :param handle_empty_element: True if this tag is known to be
            an empty-element tag (i.e. there is not expected to be any
            closing tag).
        """
        # TODO: handle namespaces here?
        attr_dict: AttributeDict = self.attribute_dict_class()
        for key, value in attrs:
            # Change None attribute values to the empty string
            # for consistency with the other tree builders.
            if value is None:
                value = ""
            if key in attr_dict:
                # A single attribute shows up multiple times in this
                # tag. How to handle it depends on the
                # on_duplicate_attribute setting.
                on_dupe = self.on_duplicate_attribute
                if on_dupe == self.IGNORE:
                    pass
                elif on_dupe in (None, self.REPLACE):
                    attr_dict[key] = value
                else:
                    on_dupe = cast(_DuplicateAttributeHandler, on_dupe)
                    on_dupe(attr_dict, key, value)
            else:
                attr_dict[key] = value
        # print("START", tag)
        sourceline: Optional[int]
        sourcepos: Optional[int]
        if self.soup.builder.store_line_numbers:
            sourceline, sourcepos = self.getpos()
        else:
            sourceline = sourcepos = None
        tagObj = self.soup.handle_starttag(
            tag, None, None, attr_dict, sourceline=sourceline, sourcepos=sourcepos
        )
        if tagObj is not None and tagObj.is_empty_element and handle_empty_element:
            # Unlike other parsers, html.parser doesn't send separate end tag
            # events for empty-element tags. (It's handled in
            # handle_startendtag, but only if the original markup looked like
            # <tag/>.)
            #
            # So we need to call handle_endtag() ourselves. Since we
            # know the start event is identical to the end event, we
            # don't want handle_endtag() to cross off any previous end
            # events for tags of this name.
            self.handle_endtag(tag, check_already_closed=False)

            # But we might encounter an explicit closing tag for this tag
            # later on. If so, we want to ignore it.
            self.already_closed_empty_element.append(tag)

        if self._root_tag_name is None:
            self._root_tag_encountered(tag)

    def handle_endtag(self, tag: str, check_already_closed: bool = True) -> None:
        """Handle a closing tag, e.g. '</tag>'

        :param tag: A tag name.
        :param check_already_closed: True if this tag is expected to
           be the closing portion of an empty-element tag,
           e.g. '<tag></tag>'.
        """
        # print("END", tag)
        if check_already_closed and tag in self.already_closed_empty_element:
            # This is a redundant end tag for an empty-element tag.
            # We've already called handle_endtag() for it, so just
            # check it off the list.
            # print("ALREADY CLOSED", tag)
            self.already_closed_empty_element.remove(tag)
        else:
            self.soup.handle_endtag(tag)

    def handle_data(self, data: str) -> None:
        """Handle some textual data that shows up between tags."""
        self.soup.handle_data(data)

    def handle_charref(self, name: str) -> None:
        """Handle a numeric character reference by converting it to the
        corresponding Unicode character and treating it as textual
        data.

        :param name: Character number, possibly in hexadecimal.
        """
        # TODO: This was originally a workaround for a bug in
        # HTMLParser. (http://bugs.python.org/issue13633) The bug has
        # been fixed, but removing this code still makes some
        # Beautiful Soup tests fail. This needs investigation.
        real_name:int
        if name.startswith("x"):
            real_name = int(name.lstrip("x"), 16)
        elif name.startswith("X"):
            real_name = int(name.lstrip("X"), 16)
        else:
            real_name = int(name)

        data, replacement_added = UnicodeDammit.numeric_character_reference(real_name)
        if replacement_added:
            self.soup.contains_replacement_characters = True
        self.handle_data(data)

    def handle_entityref(self, name: str) -> None:
        """Handle a named entity reference by converting it to the
        corresponding Unicode character(s) and treating it as textual
        data.

        :param name: Name of the entity reference.
        """
        character = EntitySubstitution.HTML_ENTITY_TO_CHARACTER.get(name)
        if character is not None:
            data = character
        else:
            # If this were XML, it would be ambiguous whether "&foo"
            # was an character entity reference with a missing
            # semicolon or the literal string "&foo". Since this is
            # HTML, we have a complete list of all character entity references,
            # and this one wasn't found, so assume it's the literal string "&foo".
            data = "&%s" % name
        self.handle_data(data)

    def handle_comment(self, data: str) -> None:
        """Handle an HTML comment.

        :param data: The text of the comment.
        """
        self.soup.endData()
        self.soup.handle_data(data)
        self.soup.endData(Comment)

    def handle_decl(self, decl: str) -> None:
        """Handle a DOCTYPE declaration.

        :param data: The text of the declaration.
        """
        self.soup.endData()
        decl = decl[len("DOCTYPE ") :]
        self.soup.handle_data(decl)
        self.soup.endData(Doctype)

    def unknown_decl(self, data: str) -> None:
        """Handle a declaration of unknown type -- probably a CDATA block.

        :param data: The text of the declaration.
        """
        cls: Type[NavigableString]
        if data.upper().startswith("CDATA["):
            cls = CData
            data = data[len("CDATA[") :]
        else:
            cls = Declaration
        self.soup.endData()
        self.soup.handle_data(data)
        self.soup.endData(cls)

    def handle_pi(self, data: str) -> None:
        """Handle a processing instruction.

        :param data: The text of the instruction.
        """
        self.soup.endData()
        self.soup.handle_data(data)
        self._document_might_be_xml(data)
        self.soup.endData(ProcessingInstruction)


class HTMLParserTreeBuilder(HTMLTreeBuilder):
    """A Beautiful soup `bs4.builder.TreeBuilder` that uses the
    :py:class:`html.parser.HTMLParser` parser, found in the Python
    standard library.

    """

    is_xml: bool = False
    picklable: bool = True
    NAME: str = HTMLPARSER
    features: Iterable[str] = [NAME, HTML, STRICT]
    parser_args: Tuple[Iterable[Any], Dict[str, Any]]

    #: The html.parser knows which line number and position in the
    #: original file is the source of an element.
    TRACKS_LINE_NUMBERS: bool = True

    def __init__(
        self,
        parser_args: Optional[Iterable[Any]] = None,
        parser_kwargs: Optional[Dict[str, Any]] = None,
        **kwargs: Any,
    ):
        """Constructor.

        :param parser_args: Positional arguments to pass into
            the BeautifulSoupHTMLParser constructor, once it's
            invoked.
        :param parser_kwargs: Keyword arguments to pass into
            the BeautifulSoupHTMLParser constructor, once it's
            invoked.
        :param kwargs: Keyword arguments for the superclass constructor.
        """
        # Some keyword arguments will be pulled out of kwargs and placed
        # into parser_kwargs.
        extra_parser_kwargs = dict()
        for arg in ("on_duplicate_attribute",):
            if arg in kwargs:
                value = kwargs.pop(arg)
                extra_parser_kwargs[arg] = value
        super(HTMLParserTreeBuilder, self).__init__(**kwargs)
        parser_args = parser_args or []
        parser_kwargs = parser_kwargs or {}
        parser_kwargs.update(extra_parser_kwargs)
        parser_kwargs["convert_charrefs"] = False
        self.parser_args = (parser_args, parser_kwargs)

    def prepare_markup(
        self,
        markup: _RawMarkup,
        user_specified_encoding: Optional[_Encoding] = None,
        document_declared_encoding: Optional[_Encoding] = None,
        exclude_encodings: Optional[_Encodings] = None,
    ) -> Iterable[Tuple[str, Optional[_Encoding], Optional[_Encoding], bool]]:
        """Run any preliminary steps necessary to make incoming markup
        acceptable to the parser.

        :param markup: Some markup -- probably a bytestring.
        :param user_specified_encoding: The user asked to try this encoding.
        :param document_declared_encoding: The markup itself claims to be
            in this encoding.
        :param exclude_encodings: The user asked _not_ to try any of
            these encodings.

        :yield: A series of 4-tuples: (markup, encoding, declared encoding,
             has undergone character replacement)

            Each 4-tuple represents a strategy for parsing the document.
            This TreeBuilder uses Unicode, Dammit to convert the markup
            into Unicode, so the ``markup`` element of the tuple will
            always be a string.
        """
        if isinstance(markup, str):
            # Parse Unicode as-is.
            yield (markup, None, None, False)
            return

        # Ask UnicodeDammit to sniff the most likely encoding.

        known_definite_encodings: List[_Encoding] = []
        if user_specified_encoding:
            # This was provided by the end-user; treat it as a known
            # definite encoding per the algorithm laid out in the
            # HTML5 spec. (See the EncodingDetector class for
            # details.)
            known_definite_encodings.append(user_specified_encoding)

        user_encodings: List[_Encoding] = []
        if document_declared_encoding:
            # This was found in the document; treat it as a slightly
            # lower-priority user encoding.
            user_encodings.append(document_declared_encoding)

        dammit = UnicodeDammit(
            markup,
            known_definite_encodings=known_definite_encodings,
            user_encodings=user_encodings,
            is_html=True,
            exclude_encodings=exclude_encodings,
        )

        if dammit.unicode_markup is None:
            # In every case I've seen, Unicode, Dammit is able to
            # convert the markup into Unicode, even if it needs to use
            # REPLACEMENT CHARACTER. But there is a code path that
            # could result in unicode_markup being None, and
            # HTMLParser can only parse Unicode, so here we handle
            # that code path.
            raise ParserRejectedMarkup(
                "Could not convert input to Unicode, and html.parser will not accept bytestrings."
            )
        else:
            yield (
                dammit.unicode_markup,
                dammit.original_encoding,
                dammit.declared_html_encoding,
                dammit.contains_replacement_characters,
            )

    def feed(self, markup: _RawMarkup, _parser_class:type[BeautifulSoupHTMLParser] =BeautifulSoupHTMLParser) -> None:
        """
        :param markup: The markup to feed into the parser.
        :param _parser_class: An HTMLParser subclass to use. This is only intended for use in unit tests.
        """
        args, kwargs = self.parser_args

        # HTMLParser.feed will only handle str, but
        # BeautifulSoup.markup is allowed to be _RawMarkup, because
        # it's set by the yield value of
        # TreeBuilder.prepare_markup. Fortunately,
        # HTMLParserTreeBuilder.prepare_markup always yields a str
        # (UnicodeDammit.unicode_markup).
        assert isinstance(markup, str)

        # We know BeautifulSoup calls TreeBuilder.initialize_soup
        # before calling feed(), so we can assume self.soup
        # is set.
        assert self.soup is not None
        parser = _parser_class(self.soup, *args, **kwargs)

        try:
            parser.feed(markup)
            parser.close()
        except AssertionError as e:
            # html.parser raises AssertionError in rare cases to
            # indicate a fatal problem with the markup, especially
            # when there's an error in the doctype declaration.
            raise ParserRejectedMarkup(e)
        parser.already_closed_empty_element = []