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parser.py
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"""A parser for HTML and XHTML.""" # This file is based on sgmllib.py, but the API is slightly different. # XXX There should be a way to distinguish between PCDATA (parsed # character data -- the normal case), RCDATA (replaceable character # data -- only char and entity references and end tags are special) # and CDATA (character data -- only end tags are special). import re import warnings import _markupbase from html import unescape __all__ = ['HTMLParser'] # Regular expressions used for parsing interesting_normal = re.compile('[&<]') incomplete = re.compile('&[a-zA-Z#]') entityref = re.compile('&([a-zA-Z][-.a-zA-Z0-9]*)[^a-zA-Z0-9]') charref = re.compile('&#(?:[0-9]+|[xX][0-9a-fA-F]+)[^0-9a-fA-F]') starttagopen = re.compile('<[a-zA-Z]') piclose = re.compile('>') commentclose = re.compile(r'--\s*>') # Note: # 1) the strict attrfind isn't really strict, but we can't make it # correctly strict without breaking backward compatibility; # 2) if you change tagfind/attrfind remember to update locatestarttagend too; # 3) if you change tagfind/attrfind and/or locatestarttagend the parser will # explode, so don't do it. tagfind = re.compile('([a-zA-Z][-.a-zA-Z0-9:_]*)(?:\s|/(?!>))*') # see http://www.w3.org/TR/html5/tokenization.html#tag-open-state # and http://www.w3.org/TR/html5/tokenization.html#tag-name-state tagfind_tolerant = re.compile('([a-zA-Z][^\t\n\r\f />\x00]*)(?:\s|/(?!>))*') attrfind = re.compile( r'\s*([a-zA-Z_][-.:a-zA-Z_0-9]*)(\s*=\s*' r'(\'[^\']*\'|"[^"]*"|[^\s"\'=<>`]*))?') attrfind_tolerant = re.compile( r'((?<=[\'"\s/])[^\s/>][^\s/=>]*)(\s*=+\s*' r'(\'[^\']*\'|"[^"]*"|(?![\'"])[^>\s]*))?(?:\s|/(?!>))*') locatestarttagend = re.compile(r""" <[a-zA-Z][-.a-zA-Z0-9:_]* # tag name (?:\s+ # whitespace before attribute name (?:[a-zA-Z_][-.:a-zA-Z0-9_]* # attribute name (?:\s*=\s* # value indicator (?:'[^']*' # LITA-enclosed value |\"[^\"]*\" # LIT-enclosed value |[^'\">\s]+ # bare value ) )? ) )* \s* # trailing whitespace """, re.VERBOSE) locatestarttagend_tolerant = re.compile(r""" <[a-zA-Z][^\t\n\r\f />\x00]* # tag name (?:[\s/]* # optional whitespace before attribute name (?:(?<=['"\s/])[^\s/>][^\s/=>]* # attribute name (?:\s*=+\s* # value indicator (?:'[^']*' # LITA-enclosed value |"[^"]*" # LIT-enclosed value |(?!['"])[^>\s]* # bare value ) (?:\s*,)* # possibly followed by a comma )?(?:\s|/(?!>))* )* )? \s* # trailing whitespace """, re.VERBOSE) endendtag = re.compile('>') # the HTML 5 spec, section 8.1.2.2, doesn't allow spaces between # </ and the tag name, so maybe this should be fixed endtagfind = re.compile('</\s*([a-zA-Z][-.a-zA-Z0-9:_]*)\s*>') class HTMLParseError(Exception): """Exception raised for all parse errors.""" def __init__(self, msg, position=(None, None)): assert msg self.msg = msg self.lineno = position[0] self.offset = position[1] def __str__(self): result = self.msg if self.lineno is not None: result = result + ", at line %d" % self.lineno if self.offset is not None: result = result + ", column %d" % (self.offset + 1) return result _default_sentinel = object() class HTMLParser(_markupbase.ParserBase): """Find tags and other markup and call handler functions. Usage: p = HTMLParser() p.feed(data) ... p.close() Start tags are handled by calling self.handle_starttag() or self.handle_startendtag(); end tags by self.handle_endtag(). The data between tags is passed from the parser to the derived class by calling self.handle_data() with the data as argument (the data may be split up in arbitrary chunks). If convert_charrefs is True the character references are converted automatically to the corresponding Unicode character (and self.handle_data() is no longer split in chunks), otherwise they are passed by calling self.handle_entityref() or self.handle_charref() with the string containing respectively the named or numeric reference as the argument. """ CDATA_CONTENT_ELEMENTS = ("script", "style") def __init__(self, strict=_default_sentinel, *, convert_charrefs=_default_sentinel): """Initialize and reset this instance. If convert_charrefs is True (default: False), all character references are automatically converted to the corresponding Unicode characters. If strict is set to False (the default) the parser will parse invalid markup, otherwise it will raise an error. Note that the strict mode and argument are deprecated. """ if strict is not _default_sentinel: warnings.warn("The strict argument and mode are deprecated.", DeprecationWarning, stacklevel=2) else: strict = False # default self.strict = strict if convert_charrefs is _default_sentinel: convert_charrefs = False # default warnings.warn("The value of convert_charrefs will become True in " "3.5. You are encouraged to set the value explicitly.", DeprecationWarning, stacklevel=2) self.convert_charrefs = convert_charrefs self.reset() def reset(self): """Reset this instance. Loses all unprocessed data.""" self.rawdata = '' self.lasttag = '???' self.interesting = interesting_normal self.cdata_elem = None _markupbase.ParserBase.reset(self) def feed(self, data): r"""Feed data to the parser. Call this as often as you want, with as little or as much text as you want (may include '\n'). """ self.rawdata = self.rawdata + data self.goahead(0) def close(self): """Handle any buffered data.""" self.goahead(1) def error(self, message): warnings.warn("The 'error' method is deprecated.", DeprecationWarning, stacklevel=2) raise HTMLParseError(message, self.getpos()) __starttag_text = None def get_starttag_text(self): """Return full source of start tag: '<...>'.""" return self.__starttag_text def set_cdata_mode(self, elem): self.cdata_elem = elem.lower() self.interesting = re.compile(r'</\s*%s\s*>' % self.cdata_elem, re.I) def clear_cdata_mode(self): self.interesting = interesting_normal self.cdata_elem = None # Internal -- handle data as far as reasonable. May leave state # and data to be processed by a subsequent call. If 'end' is # true, force handling all data as if followed by EOF marker. def goahead(self, end): rawdata = self.rawdata i = 0 n = len(rawdata) while i < n: if self.convert_charrefs and not self.cdata_elem: j = rawdata.find('<', i) if j < 0: # if we can't find the next <, either we are at the end # or there's more text incoming. If the latter is True, # we can't pass the text to handle_data in case we have # a charref cut in half at end. Try to determine if # this is the case before proceding by looking for an # & near the end and see if it's followed by a space or ;. amppos = rawdata.rfind('&', max(i, n-34)) if (amppos >= 0 and not re.compile(r'[\s;]').search(rawdata, amppos)): break # wait till we get all the text j = n else: match = self.interesting.search(rawdata, i) # < or & if match: j = match.start() else: if self.cdata_elem: break j = n if i < j: if self.convert_charrefs and not self.cdata_elem: self.handle_data(unescape(rawdata[i:j])) else: self.handle_data(rawdata[i:j]) i = self.updatepos(i, j) if i == n: break startswith = rawdata.startswith if startswith('<', i): if starttagopen.match(rawdata, i): # < + letter k = self.parse_starttag(i) elif startswith("</", i): k = self.parse_endtag(i) elif startswith("<!--", i): k = self.parse_comment(i) elif startswith("<?", i): k = self.parse_pi(i) elif startswith("<!", i): if self.strict: k = self.parse_declaration(i) else: k = self.parse_html_declaration(i) elif (i + 1) < n: self.handle_data("<") k = i + 1 else: break if k < 0: if not end: break if self.strict: self.error("EOF in middle of construct") k = rawdata.find('>', i + 1) if k < 0: k = rawdata.find('<', i + 1) if k < 0: k = i + 1 else: k += 1 if self.convert_charrefs and not self.cdata_elem: self.handle_data(unescape(rawdata[i:k])) else: self.handle_data(rawdata[i:k]) i = self.updatepos(i, k) elif startswith("&#", i): match = charref.match(rawdata, i) if match: name = match.group()[2:-1] self.handle_charref(name) k = match.end() if not startswith(';', k-1): k = k - 1 i = self.updatepos(i, k) continue else: if ";" in rawdata[i:]: # bail by consuming &# self.handle_data(rawdata[i:i+2]) i = self.updatepos(i, i+2) break elif startswith('&', i): match = entityref.match(rawdata, i) if match: name = match.group(1) self.handle_entityref(name) k = match.end() if not startswith(';', k-1): k = k - 1 i = self.updatepos(i, k) continue match = incomplete.match(rawdata, i) if match: # match.group() will contain at least 2 chars if end and match.group() == rawdata[i:]: if self.strict: self.error("EOF in middle of entity or char ref") else: k = match.end() if k <= i: k = n i = self.updatepos(i, i + 1) # incomplete break elif (i + 1) < n: # not the end of the buffer, and can't be confused # with some other construct self.handle_data("&") i = self.updatepos(i, i + 1) else: break else: assert 0, "interesting.search() lied" # end while if end and i < n and not self.cdata_elem: if self.convert_charrefs and not self.cdata_elem: self.handle_data(unescape(rawdata[i:n])) else: self.handle_data(rawdata[i:n]) i = self.updatepos(i, n) self.rawdata = rawdata[i:] # Internal -- parse html declarations, return length or -1 if not terminated # See w3.org/TR/html5/tokenization.html#markup-declaration-open-state # See also parse_declaration in _markupbase def parse_html_declaration(self, i): rawdata = self.rawdata assert rawdata[i:i+2] == '<!', ('unexpected call to ' 'parse_html_declaration()') if rawdata[i:i+4] == '<!--': # this case is actually already handled in goahead() return self.parse_comment(i) elif rawdata[i:i+3] == '<![': return self.parse_marked_section(i) elif rawdata[i:i+9].lower() == '<!doctype': # find the closing > gtpos = rawdata.find('>', i+9) if gtpos == -1: return -1 self.handle_decl(rawdata[i+2:gtpos]) return gtpos+1 else: return self.parse_bogus_comment(i) # Internal -- parse bogus comment, return length or -1 if not terminated # see http://www.w3.org/TR/html5/tokenization.html#bogus-comment-state def parse_bogus_comment(self, i, report=1): rawdata = self.rawdata assert rawdata[i:i+2] in ('<!', '</'), ('unexpected call to ' 'parse_comment()') pos = rawdata.find('>', i+2) if pos == -1: return -1 if report: self.handle_comment(rawdata[i+2:pos]) return pos + 1 # Internal -- parse processing instr, return end or -1 if not terminated def parse_pi(self, i): rawdata = self.rawdata assert rawdata[i:i+2] == '<?', 'unexpected call to parse_pi()' match = piclose.search(rawdata, i+2) # > if not match: return -1 j = match.start() self.handle_pi(rawdata[i+2: j]) j = match.end() return j # Internal -- handle starttag, return end or -1 if not terminated def parse_starttag(self, i): self.__starttag_text = None endpos = self.check_for_whole_start_tag(i) if endpos < 0: return endpos rawdata = self.rawdata self.__starttag_text = rawdata[i:endpos] # Now parse the data between i+1 and j into a tag and attrs attrs = [] if self.strict: match = tagfind.match(rawdata, i+1) else: match = tagfind_tolerant.match(rawdata, i+1) assert match, 'unexpected call to parse_starttag()' k = match.end() self.lasttag = tag = match.group(1).lower() while k < endpos: if self.strict: m = attrfind.match(rawdata, k) else: m = attrfind_tolerant.match(rawdata, k) if not m: break attrname, rest, attrvalue = m.group(1, 2, 3) if not rest: attrvalue = None elif attrvalue[:1] == '\'' == attrvalue[-1:] or \ attrvalue[:1] == '"' == attrvalue[-1:]: attrvalue = attrvalue[1:-1] if attrvalue: attrvalue = unescape(attrvalue) attrs.append((attrname.lower(), attrvalue)) k = m.end() end = rawdata[k:endpos].strip() if end not in (">", "/>"): lineno, offset = self.getpos() if "\n" in self.__starttag_text: lineno = lineno + self.__starttag_text.count("\n") offset = len(self.__starttag_text) \ - self.__starttag_text.rfind("\n") else: offset = offset + len(self.__starttag_text) if self.strict: self.error("junk characters in start tag: %r" % (rawdata[k:endpos][:20],)) self.handle_data(rawdata[i:endpos]) return endpos if end.endswith('/>'): # XHTML-style empty tag: <span attr="value" /> self.handle_startendtag(tag, attrs) else: self.handle_starttag(tag, attrs) if tag in self.CDATA_CONTENT_ELEMENTS: self.set_cdata_mode(tag) return endpos # Internal -- check to see if we have a complete starttag; return end # or -1 if incomplete. def check_for_whole_start_tag(self, i): rawdata = self.rawdata if self.strict: m = locatestarttagend.match(rawdata, i) else: m = locatestarttagend_tolerant.match(rawdata, i) if m: j = m.end() next = rawdata[j:j+1] if next == ">": return j + 1 if next == "/": if rawdata.startswith("/>", j): return j + 2 if rawdata.startswith("/", j): # buffer boundary return -1 # else bogus input if self.strict: self.updatepos(i, j + 1) self.error("malformed empty start tag") if j > i: return j else: return i + 1 if next == "": # end of input return -1 if next in ("abcdefghijklmnopqrstuvwxyz=/" "ABCDEFGHIJKLMNOPQRSTUVWXYZ"): # end of input in or before attribute value, or we have the # '/' from a '/>' ending return -1 if self.strict: self.updatepos(i, j) self.error("malformed start tag") if j > i: return j else: return i + 1 raise AssertionError("we should not get here!") # Internal -- parse endtag, return end or -1 if incomplete def parse_endtag(self, i): rawdata = self.rawdata assert rawdata[i:i+2] == "</", "unexpected call to parse_endtag" match = endendtag.search(rawdata, i+1) # > if not match: return -1 gtpos = match.end() match = endtagfind.match(rawdata, i) # </ + tag + > if not match: if self.cdata_elem is not None: self.handle_data(rawdata[i:gtpos]) return gtpos if self.strict: self.error("bad end tag: %r" % (rawdata[i:gtpos],)) # find the name: w3.org/TR/html5/tokenization.html#tag-name-state namematch = tagfind_tolerant.match(rawdata, i+2) if not namematch: # w3.org/TR/html5/tokenization.html#end-tag-open-state if rawdata[i:i+3] == '</>': return i+3 else: return self.parse_bogus_comment(i) tagname = namematch.group(1).lower() # consume and ignore other stuff between the name and the > # Note: this is not 100% correct, since we might have things like # </tag attr=">">, but looking for > after tha name should cover # most of the cases and is much simpler gtpos = rawdata.find('>', namematch.end()) self.handle_endtag(tagname) return gtpos+1 elem = match.group(1).lower() # script or style if self.cdata_elem is not None: if elem != self.cdata_elem: self.handle_data(rawdata[i:gtpos]) return gtpos self.handle_endtag(elem.lower()) self.clear_cdata_mode() return gtpos # Overridable -- finish processing of start+end tag: <tag.../> def handle_startendtag(self, tag, attrs): self.handle_starttag(tag, attrs) self.handle_endtag(tag) # Overridable -- handle start tag def handle_starttag(self, tag, attrs): pass # Overridable -- handle end tag def handle_endtag(self, tag): pass # Overridable -- handle character reference def handle_charref(self, name): pass # Overridable -- handle entity reference def handle_entityref(self, name): pass # Overridable -- handle data def handle_data(self, data): pass # Overridable -- handle comment def handle_comment(self, data): pass # Overridable -- handle declaration def handle_decl(self, decl): pass # Overridable -- handle processing instruction def handle_pi(self, data): pass def unknown_decl(self, data): if self.strict: self.error("unknown declaration: %r" % (data,)) # Internal -- helper to remove special character quoting def unescape(self, s): warnings.warn('The unescape method is deprecated and will be removed ' 'in 3.5, use html.unescape() instead.', DeprecationWarning, stacklevel=2) return unescape(s)