mirror of
https://github.com/Kozea/WeasyPrint.git
synced 2024-10-05 16:37:47 +03:00
360 lines
12 KiB
Python
360 lines
12 KiB
Python
"""Specific handling for some HTML elements, especially replaced elements.
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Replaced elements (eg. <img> elements) are rendered externally and behave as an
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atomic opaque box in CSS. In general, they may or may not have intrinsic
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dimensions. But the only replaced elements currently supported in WeasyPrint
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are images with intrinsic dimensions.
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"""
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try:
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# Available in Python 3.9+
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from importlib.resources import files
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except ImportError: # pragma: no cover
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# Deprecated in Python 3.11+
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from importlib.resources import read_text
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else:
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def read_text(package, resource):
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return (files(package) / resource).read_text('utf-8')
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import re
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from . import CSS, Attachment, css
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from .css import get_child_text
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from .css.counters import CounterStyle
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from .formatting_structure import boxes
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from .images import SVGImage
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from .logger import LOGGER
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from .urls import get_url_attribute
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HTML5_UA_COUNTER_STYLE = CounterStyle()
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HTML5_UA = read_text(css, 'html5_ua.css')
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HTML5_UA_FORM = read_text(css, 'html5_ua_form.css')
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HTML5_PH = read_text(css, 'html5_ph.css')
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HTML5_UA_STYLESHEET = CSS(
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string=HTML5_UA, counter_style=HTML5_UA_COUNTER_STYLE)
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HTML5_UA_FORM_STYLESHEET = CSS(
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string=HTML5_UA_FORM, counter_style=HTML5_UA_COUNTER_STYLE)
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HTML5_PH_STYLESHEET = CSS(string=HTML5_PH)
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# https://html.spec.whatwg.org/multipage/#space-character
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HTML_WHITESPACE = ' \t\n\f\r'
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HTML_SPACE_SEPARATED_TOKENS_RE = re.compile(f'[^{HTML_WHITESPACE}]+')
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def ascii_lower(string):
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r"""Transform (only) ASCII letters to lower case: A-Z is mapped to a-z.
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This is used for `ASCII case-insensitive
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<https://whatwg.org/C#ascii-case-insensitive>`_ matching.
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This is different from the :meth:`str.lower` method of Unicode strings
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which also affect non-ASCII characters,
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sometimes mapping them into the ASCII range:
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>>> keyword = 'Bac\N{KELVIN SIGN}ground'
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>>> assert keyword.lower() == 'background'
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>>> assert ascii_lower(keyword) != keyword.lower()
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>>> assert ascii_lower(keyword) == 'bac\N{KELVIN SIGN}ground'
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"""
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# This turns out to be faster than unicode.translate()
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return string.encode().lower().decode()
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def element_has_link_type(element, link_type):
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"""Return whether element has a ``rel`` attribute with given link type."""
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tokens = HTML_SPACE_SEPARATED_TOKENS_RE.findall(element.get('rel', ''))
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return any(ascii_lower(token) == link_type for token in tokens)
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# Maps HTML tag names to function taking an HTML element and returning a Box.
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HTML_HANDLERS = {}
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def handle_element(element, box, get_image_from_uri, base_url):
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"""Handle HTML elements that need special care.
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:returns: a (possibly empty) list of boxes.
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"""
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if box.element_tag in HTML_HANDLERS:
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return HTML_HANDLERS[element.tag](
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element, box, get_image_from_uri, base_url)
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else:
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return [box]
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def handler(tag):
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"""Return a decorator registering a function handling ``tag`` elements."""
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def decorator(function):
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"""Decorator registering a function handling ``tag`` elements."""
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HTML_HANDLERS[tag] = function
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return function
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return decorator
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def make_replaced_box(element, box, image):
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"""Wrap an image in a replaced box.
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That box is either block-level or inline-level, depending on what the
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element should be.
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"""
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type_ = (
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boxes.BlockReplacedBox if 'block' in box.style['display']
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else boxes.InlineReplacedBox)
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new_box = type_(element.tag, box.style, element, image)
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# TODO: check other attributes that need to be copied
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# TODO: find another solution
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new_box.string_set = box.string_set
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new_box.bookmark_label = box.bookmark_label
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return new_box
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@handler('img')
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def handle_img(element, box, get_image_from_uri, base_url):
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"""Handle ``<img>`` elements.
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Return either an image or the alt-text.
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See: https://www.w3.org/TR/html5/embedded-content-1.html#the-img-element
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"""
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src = get_url_attribute(element, 'src', base_url)
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alt = element.get('alt')
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if src:
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image = get_image_from_uri(
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url=src, orientation=box.style['image_orientation'])
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if image is not None:
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return [make_replaced_box(element, box, image)]
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else:
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# Invalid image, use the alt-text.
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if alt:
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box.children = [boxes.TextBox.anonymous_from(box, alt)]
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return [box]
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elif alt == '':
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# The element represents nothing
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return []
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else:
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assert alt is None
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# TODO: find some indicator that an image is missing.
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# For now, just remove the image.
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return []
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else:
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if alt:
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box.children = [boxes.TextBox.anonymous_from(box, alt)]
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return [box]
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else:
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return []
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@handler('embed')
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def handle_embed(element, box, get_image_from_uri, base_url):
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"""Handle ``<embed>`` elements, return either an image or nothing.
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See: https://www.w3.org/TR/html5/embedded-content-0.html#the-embed-element
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"""
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src = get_url_attribute(element, 'src', base_url)
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type_ = element.get('type', '').strip()
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if src:
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image = get_image_from_uri(
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url=src, forced_mime_type=type_,
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orientation=box.style['image_orientation'])
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if image is not None:
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return [make_replaced_box(element, box, image)]
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# No fallback.
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return []
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@handler('object')
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def handle_object(element, box, get_image_from_uri, base_url):
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"""Handle ``<object>`` elements, return either an image or the fallback.
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See: https://www.w3.org/TR/html5/embedded-content-0.html#the-object-element
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"""
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data = get_url_attribute(element, 'data', base_url)
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type_ = element.get('type', '').strip()
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if data:
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image = get_image_from_uri(
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url=data, forced_mime_type=type_,
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orientation=box.style['image_orientation'])
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if image is not None:
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return [make_replaced_box(element, box, image)]
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# The element’s children are the fallback.
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return [box]
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@handler('colgroup')
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def handle_colgroup(element, box, _get_image_from_uri, _base_url):
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"""Handle the ``span`` attribute."""
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if isinstance(box, boxes.TableColumnGroupBox):
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if not any(child.tag == 'col' for child in element):
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box.children = [
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boxes.TableColumnBox.anonymous_from(box, [])
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for _ in range(box.span)]
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return [box]
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@handler('col')
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def handle_col(element, box, _get_image_from_uri, _base_url):
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"""Handle the ``span`` attribute."""
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if isinstance(box, boxes.TableColumnBox) and box.span > 1:
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# Generate multiple boxes
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# https://lists.w3.org/Archives/Public/www-style/2011Nov/0293.html
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return [box.copy() for _i in range(box.span)]
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return [box]
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@handler('{http://www.w3.org/2000/svg}svg')
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def handle_svg(element, box, get_image_from_uri, base_url):
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"""Handle ``<svg>`` elements.
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Return either an image or the fallback content.
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"""
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# TODO: handle href base for inline svg tags
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url_fetcher = get_image_from_uri.keywords['url_fetcher']
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context = get_image_from_uri.keywords['context']
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try:
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image = SVGImage(element, base_url, url_fetcher, context)
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except Exception as exception: # pragma: no cover
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LOGGER.error('Failed to load inline SVG: %s', exception)
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LOGGER.debug('Error while loading inline SVG:', exc_info=exception)
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return []
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else:
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return [make_replaced_box(element, box, image)]
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def get_html_metadata(html):
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"""Get metadata dictionary out of HTML object.
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Relevant specs:
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https://www.whatwg.org/html#the-title-element
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https://www.whatwg.org/html#standard-metadata-names
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https://wiki.whatwg.org/wiki/MetaExtensions
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https://microformats.org/wiki/existing-rel-values#HTML5_link_type_extensions
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"""
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title = None
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description = None
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generator = None
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keywords = []
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authors = []
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created = None
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modified = None
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attachments = []
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custom = {}
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lang = html.etree_element.attrib.get('lang', None)
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for element in html.wrapper_element.query_all('title', 'meta', 'link'):
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element = element.etree_element
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if element.tag == 'title' and title is None:
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title = get_child_text(element)
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elif element.tag == 'meta':
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name = ascii_lower(element.get('name', ''))
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content = element.get('content', '')
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if name == 'keywords':
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for keyword in map(strip_whitespace, content.split(',')):
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if keyword not in keywords:
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keywords.append(keyword)
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elif name == 'author':
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authors.append(content)
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elif name == 'description':
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if description is None:
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description = content
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elif name == 'generator':
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if generator is None:
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generator = content
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elif name == 'dcterms.created':
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if created is None:
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created = parse_w3c_date(name, content)
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elif name == 'dcterms.modified':
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if modified is None:
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modified = parse_w3c_date(name, content)
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elif name and name not in custom:
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custom[name] = content
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elif element.tag == 'link' and element_has_link_type(
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element, 'attachment'):
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url = get_url_attribute(element, 'href', html.base_url)
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attachment_title = element.get('title', None)
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if url is None:
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LOGGER.error('Missing href in <link rel="attachment">')
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else:
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attachment = Attachment(
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url=url, description=attachment_title,
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url_fetcher=html.url_fetcher)
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attachments.append(attachment)
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return {
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'title': title,
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'description': description,
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'generator': generator,
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'keywords': keywords,
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'authors': authors,
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'created': created,
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'modified': modified,
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'attachments': attachments,
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'lang': lang,
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'custom': custom,
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}
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def strip_whitespace(string):
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"""Use the HTML definition of "space character",
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not all Unicode Whitespace.
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https://www.whatwg.org/html#strip-leading-and-trailing-whitespace
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https://www.whatwg.org/html#space-character
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"""
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return string.strip(HTML_WHITESPACE)
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# YYYY (eg 1997)
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# YYYY-MM (eg 1997-07)
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# YYYY-MM-DD (eg 1997-07-16)
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# YYYY-MM-DDThh:mmTZD (eg 1997-07-16T19:20+01:00)
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# YYYY-MM-DDThh:mm:ssTZD (eg 1997-07-16T19:20:30+01:00)
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# YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)
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W3C_DATE_RE = re.compile('''
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^
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[ \t\n\f\r]*
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(?P<year>\\d\\d\\d\\d)
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(?:
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-(?P<month>0\\d|1[012])
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(?:
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-(?P<day>[012]\\d|3[01])
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(?:
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T(?P<hour>[01]\\d|2[0-3])
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:(?P<minute>[0-5]\\d)
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(?:
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:(?P<second>[0-5]\\d)
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(?:\\.\\d+)? # Second fraction, ignored
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)?
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(?:
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Z | # UTC
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(?P<tz_hour>[+-](?:[01]\\d|2[0-3]))
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:(?P<tz_minute>[0-5]\\d)
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)
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)?
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)?
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)?
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[ \t\n\f\r]*
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$
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''', re.VERBOSE)
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def parse_w3c_date(meta_name, string):
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"""Parse datetimes as defined by the W3C.
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See https://www.w3.org/TR/NOTE-datetime
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"""
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if W3C_DATE_RE.match(string):
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return string
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else:
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LOGGER.warning(
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'Invalid date in <meta name="%s"> %r', meta_name, string)
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