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parser.py20.7 KB · 542 lines
"""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 reimport _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]')endtagopen = re.compile('</[a-zA-Z]')piclose = re.compile('>')commentclose = re.compile(r'--!?>')commentabruptclose = re.compile(r'-?>')# Note:#  1) if you change tagfind/attrfind remember to update locatetagend too;#  2) if you change tagfind/attrfind and/or locatetagend the parser will#     explode, so don't do it.# see the HTML5 specs section "13.2.5.6 Tag open state",# "13.2.5.8 Tag name state" and "13.2.5.33 Attribute name state".# https://html.spec.whatwg.org/multipage/parsing.html#tag-open-state# https://html.spec.whatwg.org/multipage/parsing.html#tag-name-state# https://html.spec.whatwg.org/multipage/parsing.html#attribute-name-statetagfind_tolerant = re.compile(r'([a-zA-Z][^\t\n\r\f />]*)(?:[\t\n\r\f ]|/(?!>))*')attrfind_tolerant = re.compile(r"""  (    (?<=['"\t\n\r\f /])[^\t\n\r\f />][^\t\n\r\f /=>]*  # attribute name   )  ([\t\n\r\f ]*=[\t\n\r\f ]*        # value indicator    ('[^']*'                        # LITA-enclosed value    |"[^"]*"                        # LIT-enclosed value    |(?!['"])[^>\t\n\r\f ]*         # bare value    )   )?  (?:[\t\n\r\f ]|/(?!>))*           # possibly followed by a space""", re.VERBOSE)locatetagend = re.compile(r"""  [a-zA-Z][^\t\n\r\f />]*           # tag name  [\t\n\r\f /]*                     # optional whitespace before attribute name  (?:(?<=['"\t\n\r\f /])[^\t\n\r\f />][^\t\n\r\f /=>]*  # attribute name    (?:[\t\n\r\f ]*=[\t\n\r\f ]*    # value indicator      (?:'[^']*'                    # LITA-enclosed value        |"[^"]*"                    # LIT-enclosed value        |(?!['"])[^>\t\n\r\f ]*     # bare value       )     )?    [\t\n\r\f /]*                   # possibly followed by a space   )*   >?""", re.VERBOSE)# The following variables are not used, but are temporarily left for# backward compatibility.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 space       )?(?:\s|/(?!>))*     )*   )?  \s*                                # trailing whitespace""", re.VERBOSE)endendtag = re.compile('>')endtagfind = re.compile(r'</\s*([a-zA-Z][-.a-zA-Z0-9:_]*)\s*>')   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.    """     # See the HTML5 specs section "13.4 Parsing HTML fragments".    # https://html.spec.whatwg.org/multipage/parsing.html#parsing-html-fragments    # CDATA_CONTENT_ELEMENTS are parsed in RAWTEXT mode    CDATA_CONTENT_ELEMENTS = ("script", "style", "xmp", "iframe", "noembed", "noframes")    RCDATA_CONTENT_ELEMENTS = ("textarea", "title")     def __init__(self, *, convert_charrefs=True, scripting=False):        """Initialize and reset this instance.         If convert_charrefs is true (the default), all character references        are automatically converted to the corresponding Unicode characters.         If *scripting* is false (the default), the content of the        ``noscript`` element is parsed normally; if it's true,        it's returned as is without being parsed.        """        self.convert_charrefs = convert_charrefs        self.scripting = scripting        self.reset()     def reset(self):        """Reset this instance.  Loses all unprocessed data."""        self.rawdata = ''        self.lasttag = '???'        self.interesting = interesting_normal        self.cdata_elem = None        self._support_cdata = True        self._escapable = True        _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)     __starttag_text = None     def get_starttag_text(self):        """Return full source of start tag: '<...>'."""        return self.__starttag_text     def set_cdata_mode(self, elem, *, escapable=False):        self.cdata_elem = elem.lower()        self._escapable = escapable        if self.cdata_elem == 'plaintext':            self.interesting = re.compile(r'\Z')        elif escapable and not self.convert_charrefs:            self.interesting = re.compile(r'&|</%s(?=[\t\n\r\f />])' % self.cdata_elem,                                          re.IGNORECASE|re.ASCII)        else:            self.interesting = re.compile(r'</%s(?=[\t\n\r\f />])' % self.cdata_elem,                                          re.IGNORECASE|re.ASCII)     def clear_cdata_mode(self):        self.interesting = interesting_normal        self.cdata_elem = None        self._escapable = True     def _set_support_cdata(self, flag=True):        """Enable or disable support of the CDATA sections.        If enabled, "<[CDATA[" starts a CDATA section which ends with "]]>".        If disabled, "<[CDATA[" starts a bogus comments which ends with ">".         This method is not called by default. Its purpose is to be called        in custom handle_starttag() and handle_endtag() methods, with        value that depends on the adjusted current node.        See https://html.spec.whatwg.org/multipage/parsing.html#markup-declaration-open-state        for details.        """        self._support_cdata = flag     # 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 proceeding 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'[\t\n\r\f ;]').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 self._escapable:                    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):                    k = self.parse_html_declaration(i)                elif (i + 1) < n or end:                    self.handle_data("<")                    k = i + 1                else:                    break                if k < 0:                    if not end:                        break                    if starttagopen.match(rawdata, i):  # < + letter                        pass                    elif startswith("</", i):                        if i + 2 == n:                            self.handle_data("</")                        elif endtagopen.match(rawdata, i):  # </ + letter                            pass                        else:                            # bogus comment                            self.handle_comment(rawdata[i+2:])                    elif startswith("<!--", i):                        j = n                        for suffix in ("--!", "--", "-"):                            if rawdata.endswith(suffix, i+4):                                j -= len(suffix)                                break                        self.handle_comment(rawdata[i+4:j])                    elif startswith("<![CDATA[", i) and self._support_cdata:                        self.unknown_decl(rawdata[i+3:])                    elif rawdata[i:i+9].lower() == '<!doctype':                        self.handle_decl(rawdata[i+2:])                    elif startswith("<!", i):                        # bogus comment                        self.handle_comment(rawdata[i+2:])                    elif startswith("<?", i):                        self.handle_pi(rawdata[i+2:])                    else:                        raise AssertionError("we should not get here!")                    k = n                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:]:                        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:            if self.convert_charrefs and self._escapable:                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+9] == '<![CDATA[' and self._support_cdata:            j = rawdata.find(']]>', i+9)            if j < 0:                return -1            self.unknown_decl(rawdata[i+3: j])            return j + 3        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        elif rawdata[i:i+3] == '<![':            j = rawdata.find('>', i+3)            if j < 0:                return -1            if rawdata[j-1] == ']':                self.unknown_decl(rawdata[i+3: j-1])            else:                self.handle_comment(rawdata[i+2: j])            return j + 1        else:            return self.parse_bogus_comment(i)     # Internal -- parse comment, return length or -1 if not terminated    # see https://html.spec.whatwg.org/multipage/parsing.html#comment-start-state    def parse_comment(self, i, report=True):        rawdata = self.rawdata        assert rawdata.startswith('<!--', i), 'unexpected call to parse_comment()'        match = commentclose.search(rawdata, i+4)        if not match:            match = commentabruptclose.match(rawdata, i+4)            if not match:                return -1        if report:            j = match.start()            self.handle_comment(rawdata[i+4: j])        return match.end()     # Internal -- parse bogus comment, return length or -1 if not terminated    # see https://html.spec.whatwg.org/multipage/parsing.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):        # See the HTML5 specs section "13.2.5.8 Tag name state"        # https://html.spec.whatwg.org/multipage/parsing.html#tag-name-state        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 = []        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:            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)            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 or                (self.scripting and tag == "noscript") or                tag == "plaintext"):                self.set_cdata_mode(tag, escapable=False)            elif tag in self.RCDATA_CONTENT_ELEMENTS:                self.set_cdata_mode(tag, escapable=True)        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        match = locatetagend.match(rawdata, i+1)        assert match        j = match.end()        if rawdata[j-1] != ">":            return -1        return j     # Internal -- parse endtag, return end or -1 if incomplete    def parse_endtag(self, i):        # See the HTML5 specs section "13.2.5.7 End tag open state"        # https://html.spec.whatwg.org/multipage/parsing.html#end-tag-open-state        rawdata = self.rawdata        assert rawdata[i:i+2] == "</", "unexpected call to parse_endtag"        if rawdata.find('>', i+2) < 0:  # fast check            return -1        if not endtagopen.match(rawdata, i):  # </ + letter            if rawdata[i+2:i+3] == '>':  # </> is ignored                # "missing-end-tag-name" parser error                return i+3            else:                return self.parse_bogus_comment(i)         match = locatetagend.match(rawdata, i+2)        assert match        j = match.end()        if rawdata[j-1] != ">":            return -1         # find the name: "13.2.5.8 Tag name state"        # https://html.spec.whatwg.org/multipage/parsing.html#tag-name-state        match = tagfind_tolerant.match(rawdata, i+2)        assert match        tag = match.group(1).lower()        self.handle_endtag(tag)        self.clear_cdata_mode()        return j     # 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):        pass