229 lines
7.3 KiB
Python
229 lines
7.3 KiB
Python
"""Compare two HTML documents."""
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import re
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from html.parser import HTMLParser
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WHITESPACE = re.compile(r'\s+')
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def normalize_whitespace(string):
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return WHITESPACE.sub(' ', string)
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class Element:
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def __init__(self, name, attributes):
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self.name = name
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self.attributes = sorted(attributes)
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self.children = []
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def append(self, element):
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if isinstance(element, str):
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element = normalize_whitespace(element)
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if self.children:
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if isinstance(self.children[-1], str):
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self.children[-1] += element
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self.children[-1] = normalize_whitespace(self.children[-1])
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return
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elif self.children:
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# removing last children if it is only whitespace
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# this can result in incorrect dom representations since
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# whitespace between inline tags like <span> is significant
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if isinstance(self.children[-1], str):
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if self.children[-1].isspace():
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self.children.pop()
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if element:
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self.children.append(element)
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def finalize(self):
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def rstrip_last_element(children):
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if children:
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if isinstance(children[-1], str):
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children[-1] = children[-1].rstrip()
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if not children[-1]:
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children.pop()
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children = rstrip_last_element(children)
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return children
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rstrip_last_element(self.children)
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for i, child in enumerate(self.children):
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if isinstance(child, str):
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self.children[i] = child.strip()
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elif hasattr(child, 'finalize'):
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child.finalize()
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def __eq__(self, element):
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if not hasattr(element, 'name') or self.name != element.name:
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return False
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if len(self.attributes) != len(element.attributes):
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return False
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if self.attributes != element.attributes:
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# attributes without a value is same as attribute with value that
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# equals the attributes name:
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# <input checked> == <input checked="checked">
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for i in range(len(self.attributes)):
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attr, value = self.attributes[i]
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other_attr, other_value = element.attributes[i]
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if value is None:
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value = attr
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if other_value is None:
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other_value = other_attr
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if attr != other_attr or value != other_value:
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return False
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return self.children == element.children
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def __hash__(self):
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return hash((self.name,) + tuple(a for a in self.attributes))
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def _count(self, element, count=True):
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if not isinstance(element, str):
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if self == element:
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return 1
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if isinstance(element, RootElement):
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if self.children == element.children:
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return 1
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i = 0
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for child in self.children:
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# child is text content and element is also text content, then
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# make a simple "text" in "text"
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if isinstance(child, str):
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if isinstance(element, str):
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if count:
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i += child.count(element)
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elif element in child:
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return 1
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else:
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i += child._count(element, count=count)
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if not count and i:
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return i
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return i
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def __contains__(self, element):
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return self._count(element, count=False) > 0
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def count(self, element):
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return self._count(element, count=True)
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def __getitem__(self, key):
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return self.children[key]
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def __str__(self):
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output = '<%s' % self.name
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for key, value in self.attributes:
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if value:
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output += ' %s="%s"' % (key, value)
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else:
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output += ' %s' % key
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if self.children:
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output += '>\n'
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output += ''.join(str(c) for c in self.children)
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output += '\n</%s>' % self.name
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else:
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output += '>'
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return output
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def __repr__(self):
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return str(self)
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class RootElement(Element):
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def __init__(self):
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super().__init__(None, ())
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def __str__(self):
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return ''.join(str(c) for c in self.children)
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class HTMLParseError(Exception):
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pass
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class Parser(HTMLParser):
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SELF_CLOSING_TAGS = (
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'br', 'hr', 'input', 'img', 'meta', 'spacer', 'link', 'frame', 'base',
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'col',
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)
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def __init__(self):
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super().__init__(convert_charrefs=False)
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self.root = RootElement()
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self.open_tags = []
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self.element_positions = {}
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def error(self, msg):
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raise HTMLParseError(msg, self.getpos())
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def format_position(self, position=None, element=None):
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if not position and element:
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position = self.element_positions[element]
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if position is None:
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position = self.getpos()
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if hasattr(position, 'lineno'):
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position = position.lineno, position.offset
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return 'Line %d, Column %d' % position
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@property
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def current(self):
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if self.open_tags:
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return self.open_tags[-1]
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else:
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return self.root
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def handle_startendtag(self, tag, attrs):
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self.handle_starttag(tag, attrs)
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if tag not in self.SELF_CLOSING_TAGS:
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self.handle_endtag(tag)
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def handle_starttag(self, tag, attrs):
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# Special case handling of 'class' attribute, so that comparisons of DOM
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# instances are not sensitive to ordering of classes.
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attrs = [
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(name, " ".join(sorted(value.split(" "))))
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if name == "class"
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else (name, value)
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for name, value in attrs
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]
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element = Element(tag, attrs)
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self.current.append(element)
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if tag not in self.SELF_CLOSING_TAGS:
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self.open_tags.append(element)
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self.element_positions[element] = self.getpos()
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def handle_endtag(self, tag):
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if not self.open_tags:
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self.error("Unexpected end tag `%s` (%s)" % (
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tag, self.format_position()))
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element = self.open_tags.pop()
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while element.name != tag:
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if not self.open_tags:
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self.error("Unexpected end tag `%s` (%s)" % (
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tag, self.format_position()))
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element = self.open_tags.pop()
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def handle_data(self, data):
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self.current.append(data)
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def handle_charref(self, name):
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self.current.append('&%s;' % name)
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def handle_entityref(self, name):
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self.current.append('&%s;' % name)
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def parse_html(html):
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"""
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Take a string that contains *valid* HTML and turn it into a Python object
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structure that can be easily compared against other HTML on semantic
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equivalence. Syntactical differences like which quotation is used on
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arguments will be ignored.
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"""
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parser = Parser()
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parser.feed(html)
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parser.close()
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document = parser.root
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document.finalize()
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# Removing ROOT element if it's not necessary
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if len(document.children) == 1:
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if not isinstance(document.children[0], str):
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document = document.children[0]
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return document
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