path: root/lib/mako/lexer.py

# lexer.py
# Copyright (C) 2006, 2007, 2008 Michael Bayer mike_mp@zzzcomputing.com
#
# This module is part of Mako and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

"""provides the Lexer class for parsing template strings into parse trees."""

import re, codecs
from mako import parsetree, exceptions
from mako.pygen import adjust_whitespace

_regexp_cache = {}

class Lexer(object):
    def __init__(self, text, filename=None, disable_unicode=False, input_encoding=None, preprocessor=None):
        self.text = text
        self.filename = filename
        self.template = parsetree.TemplateNode(self.filename)
        self.matched_lineno = 1
        self.matched_charpos = 0
        self.lineno = 1
        self.match_position = 0
        self.tag = []
        self.control_line = []
        self.disable_unicode = disable_unicode
        self.encoding = input_encoding
        if preprocessor is None:
            self.preprocessor = []
        elif not hasattr(preprocessor, '__iter__'):
            self.preprocessor = [preprocessor]
        else:
            self.preprocessor = preprocessor
            
    exception_kwargs = property(lambda self:{'source':self.text, 'lineno':self.matched_lineno, 'pos':self.matched_charpos, 'filename':self.filename})
    
    def match(self, regexp, flags=None):
        """match the given regular expression string and flags to the current text position.
        
        if a match occurs, update the current text and line position."""
        mp = self.match_position
        try:
            reg = _regexp_cache[(regexp, flags)]
        except KeyError:
            if flags:
                reg = re.compile(regexp, flags)
            else:
                reg = re.compile(regexp)
            _regexp_cache[(regexp, flags)] = reg

        match = reg.match(self.text, self.match_position)
        if match:
            (start, end) = match.span()
            if end == start:
                self.match_position = end + 1
            else:
                self.match_position = end
            self.matched_lineno = self.lineno
            lines = re.findall(r"\n", self.text[mp:self.match_position])
            cp = mp - 1
            while (cp >= 0 and cp<self.textlength and self.text[cp] != '\n'):
                cp -=1
            self.matched_charpos = mp - cp
            self.lineno += len(lines)
            #print "MATCHED:", match.group(0), "LINE START:", self.matched_lineno, "LINE END:", self.lineno
        #print "MATCH:", regexp, "\n", self.text[mp : mp + 15], (match and "TRUE" or "FALSE")
        return match
    
    def parse_until_text(self, *text):
        startpos = self.match_position
        while True:
            match = self.match(r'#.*\n')
            if match:
                continue
            match = self.match(r'(\"\"\"|\'\'\'|\"|\')')
            if match:
                m = self.match(r'.*?%s' % match.group(1), re.S)
                if not m:
                    raise exceptions.SyntaxException("Unmatched '%s'" % match.group(1), **self.exception_kwargs)
            else:
                match = self.match(r'(%s)' % r'|'.join(text))
                if match:
                    return (self.text[startpos:self.match_position-len(match.group(1))], match.group(1))
                else:
                    match = self.match(r".*?(?=\"|\'|#|%s)" % r'|'.join(text), re.S)
                    if not match:
                        raise exceptions.SyntaxException("Expected: %s" % ','.join(text), **self.exception_kwargs)
                
    def append_node(self, nodecls, *args, **kwargs):
        kwargs.setdefault('source', self.text)
        kwargs.setdefault('lineno', self.matched_lineno)
        kwargs.setdefault('pos', self.matched_charpos)
        kwargs['filename'] = self.filename
        node = nodecls(*args, **kwargs)
        if len(self.tag):
            self.tag[-1].nodes.append(node)
        else:
            self.template.nodes.append(node)
        if isinstance(node, parsetree.Tag):
            if len(self.tag):
                node.parent = self.tag[-1]
            self.tag.append(node)
        elif isinstance(node, parsetree.ControlLine):
            if node.isend:
                self.control_line.pop()
            elif node.is_primary:
                self.control_line.append(node)
            elif len(self.control_line) and not self.control_line[-1].is_ternary(node.keyword):
                raise exceptions.SyntaxException("Keyword '%s' not a legal ternary for keyword '%s'" % (node.keyword, self.control_line[-1].keyword), **self.exception_kwargs)

    def escape_code(self, text):
        if not self.disable_unicode and self.encoding:
            return text.encode('ascii', 'backslashreplace')
        else:
            return text
            
    def parse(self):
        for preproc in self.preprocessor:
            self.text = preproc(self.text)
        if not isinstance(self.text, unicode) and self.text.startswith(codecs.BOM_UTF8):
            self.text = self.text[len(codecs.BOM_UTF8):]
            parsed_encoding = 'utf-8'
            me = self.match_encoding()
            if me is not None and me != 'utf-8':
                raise exceptions.CompileException("Found utf-8 BOM in file, with conflicting magic encoding comment of '%s'" % me, self.text.decode('utf-8', 'ignore'), 0, 0, self.filename)
        else:
            parsed_encoding = self.match_encoding()
        if parsed_encoding:
            self.encoding = parsed_encoding
        if not self.disable_unicode and not isinstance(self.text, unicode):
            if self.encoding:
                try:
                    self.text = self.text.decode(self.encoding)
                except UnicodeDecodeError, e:
                    raise exceptions.CompileException("Unicode decode operation of encoding '%s' failed" % self.encoding, self.text.decode('utf-8', 'ignore'), 0, 0, self.filename)
            else:
                try:
                    self.text = self.text.decode()
                except UnicodeDecodeError, e:
                    raise exceptions.CompileException("Could not read template using encoding of 'ascii'.  Did you forget a magic encoding comment?", self.text.decode('utf-8', 'ignore'), 0, 0, self.filename)

        self.textlength = len(self.text)
            
        while (True):
            if self.match_position > self.textlength: 
                break
        
            if self.match_end():
                break
            if self.match_expression():
                continue
            if self.match_control_line():
                continue
            if self.match_comment():
                continue
            if self.match_tag_start(): 
                continue
            if self.match_tag_end():
                continue
            if self.match_python_block():
                continue
            if self.match_text(): 
                continue
            
            if self.match_position > self.textlength: 
                break
            raise exceptions.CompileException("assertion failed")
            
        if len(self.tag):
            raise exceptions.SyntaxException("Unclosed tag: <%%%s>" % self.tag[-1].keyword, **self.exception_kwargs)
        if len(self.control_line):
            raise exceptions.SyntaxException("Unterminated control keyword: '%s'" % self.control_line[-1].keyword, self.text, self.control_line[-1].lineno, self.control_line[-1].pos, self.filename)
        return self.template

    def match_encoding(self):
        match = self.match(r'#.*coding[:=]\s*([-\w.]+).*\r?\n')
        if match:
            return match.group(1)
        else:
            return None
            
    def match_tag_start(self):
        match = self.match(r'''
            \<%     # opening tag
            
            (\w+)   # keyword
            
            ((?:\s+\w+|=|".*?"|'.*?')*)  # attrname, = sign, string expression
            
            \s*     # more whitespace
            
            (/)?>   # closing
            
            ''', 
            
            re.I | re.S | re.X)
            
        if match:
            (keyword, attr, isend) = (match.group(1).lower(), match.group(2), match.group(3))
            self.keyword = keyword
            attributes = {}
            if attr:
                for att in re.findall(r"\s*(\w+)\s*=\s*(?:'([^']*)'|\"([^\"]*)\")", attr):
                    (key, val1, val2) = att
                    text = val1 or val2
                    text = text.replace('\r\n', '\n')
                    attributes[key] = self.escape_code(text)
            self.append_node(parsetree.Tag, keyword, attributes)
            if isend:
                self.tag.pop()
            else:
                if keyword == 'text':
                    match = self.match(r'(.*?)(?=\</%text>)',  re.S)
                    if not match:
                        raise exceptions.SyntaxException("Unclosed tag: <%%%s>" % self.tag[-1].keyword, **self.exception_kwargs)
                    self.append_node(parsetree.Text, match.group(1))
                    return self.match_tag_end()
            return True
        else: 
            return False
        
    def match_tag_end(self):
        match = self.match(r'\</%[\t ]*(.+?)[\t ]*>')
        if match:
            if not len(self.tag):
                raise exceptions.SyntaxException("Closing tag without opening tag: </%%%s>" % match.group(1), **self.exception_kwargs)
            elif self.tag[-1].keyword != match.group(1):
                raise exceptions.SyntaxException("Closing tag </%%%s> does not match tag: <%%%s>" % (match.group(1), self.tag[-1].keyword), **self.exception_kwargs)
            self.tag.pop()
            return True
        else:
            return False
            
    def match_end(self):
        match = self.match(r'\Z', re.S)
        if match:
            string = match.group()
            if string:
                return string
            else:
                return True
        else:
            return False
    
    def match_text(self):
        match = self.match(r"""
                (.*?)         # anything, followed by:
                (
                 (?<=\n)(?=[ \t]*(?=%|\#\#)) # an eval or line-based comment preceded by a consumed \n and whitespace
                 |
                 (?=\${)   # an expression
                 |
                 (?=\#\*) # multiline comment
                 |
                 (?=</?[%&])  # a substitution or block or call start or end
                                              # - don't consume
                 |
                 (\\\r?\n)         # an escaped newline  - throw away
                 |
                 \Z           # end of string
                )""", re.X | re.S)
        
        if match:
            text = match.group(1)
            self.append_node(parsetree.Text, text)
            return True
        else:
            return False
    
    def match_python_block(self):
        match = self.match(r"<%(!)?")
        if match:
            (line, pos) = (self.matched_lineno, self.matched_charpos)
            (text, end) = self.parse_until_text(r'%>')
            text = adjust_whitespace(text) + "\n"   # the trailing newline helps compiler.parse() not complain about indentation
            self.append_node(parsetree.Code, self.escape_code(text), match.group(1)=='!', lineno=line, pos=pos)
            return True
        else:
            return False
            
    def match_expression(self):
        match = self.match(r"\${")
        if match:
            (line, pos) = (self.matched_lineno, self.matched_charpos)
            (text, end) = self.parse_until_text(r'\|', r'}')
            if end == '|':
                (escapes, end) = self.parse_until_text(r'}')
            else:
                escapes = ""
            text = text.replace('\r\n', '\n')
            self.append_node(parsetree.Expression, self.escape_code(text), escapes.strip(), lineno=line, pos=pos)
            return True
        else:
            return False

    def match_control_line(self):
        match = self.match(r"(?<=^)[\t ]*(%|##)[\t ]*((?:(?:\\r?\n)|[^\r\n])*)(?:\r?\n|\Z)", re.M)
        if match:
            operator = match.group(1)
            text = match.group(2)
            if operator == '%':
                m2 = re.match(r'(end)?(\w+)\s*(.*)', text)
                if not m2:
                    raise exceptions.SyntaxException("Invalid control line: '%s'" % text, **self.exception_kwargs)
                (isend, keyword) = m2.group(1, 2)
                isend = (isend is not None)
                
                if isend:
                    if not len(self.control_line):
                        raise exceptions.SyntaxException("No starting keyword '%s' for '%s'" % (keyword, text), **self.exception_kwargs)
                    elif self.control_line[-1].keyword != keyword:
                        raise exceptions.SyntaxException("Keyword '%s' doesn't match keyword '%s'" % (text, self.control_line[-1].keyword), **self.exception_kwargs)
                self.append_node(parsetree.ControlLine, keyword, isend, self.escape_code(text))
            else:
                self.append_node(parsetree.Comment, text)
            return True
        else:
            return False

    def match_comment(self):
        """matches the multiline version of a comment"""
        match = self.match(r"<%doc>(.*?)</%doc>", re.S)
        if match:
            self.append_node(parsetree.Comment, match.group(1))
            return True
        else:
            return False