# -*- coding: utf-8 -*- """ jinja.lexer ~~~~~~~~~~~ This module implements a Jinja / Python combination lexer. The `Lexer` class provided by this module is used to do some preprocessing for Jinja. On the one hand it filters out invalid operators like the bitshift operators we don't allow in templates. On the other hand it separates template code and python code in expressions. Because of some limitations in the compiler package which are just natural but annoying for Jinja, the lexer also "escapes" non names that are not keywords. The Jinja parser then removes those escaping marks again. This is required in order to make "class" and some other python keywords we don't use valid identifiers. :copyright: 2007 by Armin Ronacher. :license: BSD, see LICENSE for more details. """ import re import unicodedata from jinja.datastructure import TokenStream, Token from jinja.exceptions import TemplateSyntaxError from jinja.utils import set, sorted from weakref import WeakValueDictionary __all__ = ['Lexer', 'Failure', 'keywords'] # cache for the lexers. Exists in order to be able to have multiple # environments with the same lexer _lexer_cache = WeakValueDictionary() # static regular expressions whitespace_re = re.compile(r'\s+(?um)') name_re = re.compile(r'[a-zA-Z_][a-zA-Z0-9_]*') string_re = re.compile(r"('([^'\\]*(?:\\.[^'\\]*)*)'" r'|"([^"\\]*(?:\\.[^"\\]*)*)")(?ms)') integer_re = re.compile(r'\d+') float_re = re.compile(r'\d+\.\d+') regex_re = re.compile(r'@/([^/\\]*(?:\\.[^/\\]*)*)*/[a-z]*(?ms)') # set of used keywords keywords = set(['and', 'block', 'cycle', 'elif', 'else', 'endblock', 'endfilter', 'endfor', 'endif', 'endmacro', 'endraw', 'endtrans', 'extends', 'filter', 'for', 'if', 'in', 'include', 'is', 'macro', 'not', 'or', 'pluralize', 'raw', 'recursive', 'set', 'trans', 'print', 'call', 'endcall']) # bind operators to token types operators = { '+': 'add', '-': 'sub', '/': 'div', '//': 'floordiv', '*': 'mul', '%': 'mod', '**': 'pow', '~': 'tilde', '!': 'bang', '@': 'at', '[': 'lbracket', ']': 'rbracket', '(': 'lparen', ')': 'rparen', '{': 'lbrace', '}': 'rbrace', '==': 'eq', '!=': 'ne', '>': 'gt', '>=': 'gteq', '<': 'lt', '<=': 'lteq', '=': 'assign', '.': 'dot', ':': 'colon', '|': 'pipe', ',': 'comma' } reverse_operators = dict([(v, k) for k, v in operators.iteritems()]) assert len(operators) == len(reverse_operators), 'operators dropped' operator_re = re.compile('(%s)' % '|'.join([re.escape(x) for x in sorted(operators, key=lambda x: -len(x))])) def unescape_string(lineno, filename, s): r""" Unescape a string. Supported escapes: \a, \n, \r\, \f, \v, \\, \", \', \0 \x00, \u0000, \U00000000, \N{...} Not supported are \101 because imho redundant. """ result = [] write = result.append simple_escapes = { 'a': '\a', 'n': '\n', 'r': '\r', 'f': '\f', 't': '\t', 'v': '\v', '\\': '\\', '"': '"', "'": "'", '0': '\x00' } unicode_escapes = { 'x': 2, 'u': 4, 'U': 8 } chariter = iter(s) next_char = chariter.next try: for char in chariter: if char == '\\': char = next_char() if char in simple_escapes: write(simple_escapes[char]) elif char in unicode_escapes: seq = [next_char() for x in xrange(unicode_escapes[char])] try: write(unichr(int(''.join(seq), 16))) except ValueError: raise TemplateSyntaxError('invalid unicode codepoint', lineno, filename) elif char == 'N': if next_char() != '{': raise TemplateSyntaxError('no name for codepoint', lineno, filename) seq = [] while True: char = next_char() if char == '}': break seq.append(char) try: write(unicodedata.lookup(u''.join(seq))) except KeyError: raise TemplateSyntaxError('unknown character name', lineno, filename) else: write('\\' + char) else: write(char) except StopIteration: raise TemplateSyntaxError('invalid string escape', lineno, filename) return u''.join(result) def unescape_regex(s): """ Unescape rules for regular expressions. """ buffer = [] write = buffer.append in_escape = False for char in s: if in_escape: in_escape = False if char not in safe_chars: write('\\' + char) continue write(char) return u''.join(buffer) class Failure(object): """ Class that raises a `TemplateSyntaxError` if called. Used by the `Lexer` to specify known errors. """ def __init__(self, message, cls=TemplateSyntaxError): self.message = message self.error_class = cls def __call__(self, lineno, filename): raise self.error_class(self.message, lineno, filename) class LexerMeta(type): """ Metaclass for the lexer that caches instances for the same configuration in a weak value dictionary. """ def __call__(cls, environment): key = hash((environment.block_start_string, environment.block_end_string, environment.variable_start_string, environment.variable_end_string, environment.comment_start_string, environment.comment_end_string, environment.trim_blocks)) # use the cached lexer if possible if key in _lexer_cache: return _lexer_cache[key] # create a new lexer and cache it lexer = type.__call__(cls, environment) _lexer_cache[key] = lexer return lexer class Lexer(object): """ Class that implements a lexer for a given environment. Automatically created by the environment class, usually you don't have to do that. Note that the lexer is not automatically bound to an environment. Multiple environments can share the same lexer. """ __metaclass__ = LexerMeta def __init__(self, environment): # shortcuts c = lambda x: re.compile(x, re.M | re.S) e = re.escape # lexing rules for tags tag_rules = [ (whitespace_re, None, None), (float_re, 'float', None), (integer_re, 'integer', None), (name_re, 'name', None), (string_re, 'string', None), (regex_re, 'regex', None), (operator_re, 'operator', None) ] #: if variables and blocks have the same delimiters we won't #: receive any variable blocks in the parser. This variable is `True` #: if we need that. self.no_variable_block = ( (environment.variable_start_string is environment.variable_end_string is None) or (environment.variable_start_string == environment.block_start_string and environment.variable_end_string == environment.block_end_string) ) # assamble the root lexing rule. because "|" is ungreedy # we have to sort by length so that the lexer continues working # as expected when we have parsing rules like <% for block and # <%= for variables. (if someone wants asp like syntax) # variables are just part of the rules if variable processing # is required. root_tag_rules = [ ('comment', environment.comment_start_string), ('block', environment.block_start_string) ] if not self.no_variable_block: root_tag_rules.append(('variable', environment.variable_start_string)) root_tag_rules.sort(lambda a, b: cmp(len(b[1]), len(a[1]))) # block suffix if trimming is enabled block_suffix_re = environment.trim_blocks and '\\n?' or '' # global lexing rules self.rules = { 'root': [ # directives (c('(.*?)(?:%s)' % '|'.join( ['(?P(?:\s*%s\-|%s)\s*raw\s*%s)' % ( e(environment.block_start_string), e(environment.block_start_string), e(environment.block_end_string) )] + [ '(?P<%s_begin>\s*%s\-|%s)' % (n, e(r), e(r)) for n, r in root_tag_rules ])), ('data', '#bygroup'), '#bygroup'), # data (c('.+'), 'data', None) ], # comments 'comment_begin': [ (c(r'(.*?)((?:\-%s\s*|%s)%s)' % ( e(environment.comment_end_string), e(environment.comment_end_string), block_suffix_re )), ('comment', 'comment_end'), '#pop'), (c('(.)'), (Failure('Missing end of comment tag'),), None) ], # blocks 'block_begin': [ (c('(?:\-%s\s*|%s)%s' % ( e(environment.block_end_string), e(environment.block_end_string), block_suffix_re )), 'block_end', '#pop'), ] + tag_rules, # raw block 'raw_begin': [ (c('(.*?)((?:\s*%s\-|%s)\s*endraw\s*(?:\-%s\s*|%s%s))' % ( e(environment.block_start_string), e(environment.block_start_string), e(environment.block_end_string), e(environment.block_end_string), block_suffix_re )), ('data', 'raw_end'), '#pop'), (c('(.)'), (Failure('Missing end of raw directive'),), None) ] } # only add the variable rules to the list if we process variables # the variable_end_string variable could be None and break things. if not self.no_variable_block: self.rules['variable_begin'] = [ (c('\-%s\s*|%s' % ( e(environment.variable_end_string), e(environment.variable_end_string) )), 'variable_end', '#pop') ] + tag_rules def tokenize(self, source, filename=None): """ Works like `tokeniter` but returns a tokenstream of tokens and not a generator or token tuples. Additionally all token values are already converted into types and postprocessed. For example keywords are already keyword tokens, not named tokens, comments are removed, integers and floats converted, strings unescaped etc. """ def generate(): for lineno, token, value in self.tokeniter(source, filename): if token in ('comment_begin', 'comment', 'comment_end'): continue elif token == 'data': try: value = str(value) except UnicodeError: pass elif token == 'name': value = str(value) if value in keywords: token = value value = '' elif token == 'string': value = unescape_string(lineno, filename, value[1:-1]) try: value = str(value) except UnicodeError: pass elif token == 'regex': args = value[value.rfind('/') + 1:] value = unescape_regex(value[2:-(len(args) + 1)]) if args: value = '(?%s)%s' % (args, value) elif token == 'integer': value = int(value) elif token == 'float': value = float(value) elif token == 'operator': token = operators[value] value = '' yield Token(lineno, token, value) return TokenStream(generate(), filename) def tokeniter(self, source, filename=None): """ This method tokenizes the text and returns the tokens in a generator. Use this method if you just want to tokenize a template. The output you get is not compatible with the input the jinja parser wants. The parser uses the `tokenize` function with returns a `TokenStream` and keywords instead of just names. """ source = '\n'.join(source.splitlines()) pos = 0 lineno = 1 stack = ['root'] statetokens = self.rules['root'] source_length = len(source) balancing_stack = [] while True: # tokenizer loop for regex, tokens, new_state in statetokens: m = regex.match(source, pos) # if no match we try again with the next rule if not m: continue # we only match blocks and variables if brances / parentheses # are balanced. continue parsing with the lower rule which # is the operator rule. do this only if the end tags look # like operators if balancing_stack and \ tokens in ('variable_end', 'block_end'): continue # tuples support more options if isinstance(tokens, tuple): for idx, token in enumerate(tokens): # hidden group if token is None: g = m.group(idx) if g: lineno += g.count('\n') continue # failure group elif token.__class__ is Failure: raise token(lineno, filename) # bygroup is a bit more complex, in that case we # yield for the current token the first named # group that matched elif token == '#bygroup': for key, value in m.groupdict().iteritems(): if value is not None: yield lineno, key, value lineno += value.count('\n') break else: raise RuntimeError('%r wanted to resolve ' 'the token dynamically' ' but no group matched' % regex) # normal group else: data = m.group(idx + 1) if data: yield lineno, token, data lineno += data.count('\n') # strings as token just are yielded as it, but just # if the data is not empty else: data = m.group() # update brace/parentheses balance if tokens == 'operator': if data == '{': balancing_stack.append('}') elif data == '(': balancing_stack.append(')') elif data == '[': balancing_stack.append(']') elif data in ('}', ')', ']'): if not balancing_stack: raise TemplateSyntaxError('unexpected "%s"' % data, lineno, filename) expected_op = balancing_stack.pop() if expected_op != data: raise TemplateSyntaxError('unexpected "%s", ' 'expected "%s"' % (data, expected_op), lineno, filename) # yield items if tokens is not None: if data: yield lineno, tokens, data lineno += data.count('\n') # fetch new position into new variable so that we can check # if there is a internal parsing error which would result # in an infinite loop pos2 = m.end() # handle state changes if new_state is not None: # remove the uppermost state if new_state == '#pop': stack.pop() # resolve the new state by group checking elif new_state == '#bygroup': for key, value in m.groupdict().iteritems(): if value is not None: stack.append(key) break else: raise RuntimeError('%r wanted to resolve the ' 'new state dynamically but' ' no group matched' % regex) # direct state name given else: stack.append(new_state) statetokens = self.rules[stack[-1]] # we are still at the same position and no stack change. # this means a loop without break condition, avoid that and # raise error elif pos2 == pos: raise RuntimeError('%r yielded empty string without ' 'stack change' % regex) # publish new function and start again pos = pos2 break # if loop terminated without break we havn't found a single match # either we are at the end of the file or we have a problem else: # end of text if pos >= source_length: return # something went wrong raise TemplateSyntaxError('unexpected char %r at %d' % (source[pos], pos), lineno, filename)