Mercurial > genshi > mirror
view genshi/template/interpolation.py @ 991:0d4e1bafad8f stable-0.6.x
Merge r1213 from trunk (fix infinite loop in interpolation brace matching caused by a change in 2.7).
author | hodgestar |
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date | Sat, 26 Jan 2013 11:59:30 +0000 |
parents | f3d998cc941e |
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# -*- coding: utf-8 -*- # # Copyright (C) 2007-2009 Edgewall Software # All rights reserved. # # This software is licensed as described in the file COPYING, which # you should have received as part of this distribution. The terms # are also available at http://genshi.edgewall.org/wiki/License. # # This software consists of voluntary contributions made by many # individuals. For the exact contribution history, see the revision # history and logs, available at http://genshi.edgewall.org/log/. """String interpolation routines, i.e. the splitting up a given text into some parts that are literal strings, and others that are Python expressions. """ from itertools import chain import os import re from tokenize import PseudoToken from genshi.core import TEXT from genshi.template.base import TemplateSyntaxError, EXPR from genshi.template.eval import Expression __all__ = ['interpolate'] __docformat__ = 'restructuredtext en' NAMESTART = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_' NAMECHARS = NAMESTART + '.0123456789' PREFIX = '$' token_re = re.compile('%s|%s(?s)' % ( r'[uU]?[rR]?("""|\'\'\')((?<!\\)\\\1|.)*?\1', PseudoToken )) def interpolate(text, filepath=None, lineno=-1, offset=0, lookup='strict'): """Parse the given string and extract expressions. This function is a generator that yields `TEXT` events for literal strings, and `EXPR` events for expressions, depending on the results of parsing the string. >>> for kind, data, pos in interpolate("hey ${foo}bar"): ... print('%s %r' % (kind, data)) TEXT 'hey ' EXPR Expression('foo') TEXT 'bar' :param text: the text to parse :param filepath: absolute path to the file in which the text was found (optional) :param lineno: the line number at which the text was found (optional) :param offset: the column number at which the text starts in the source (optional) :param lookup: the variable lookup mechanism; either "lenient" (the default), "strict", or a custom lookup class :return: a list of `TEXT` and `EXPR` events :raise TemplateSyntaxError: when a syntax error in an expression is encountered """ pos = [filepath, lineno, offset] textbuf = [] textpos = None for is_expr, chunk in chain(lex(text, pos, filepath), [(True, '')]): if is_expr: if textbuf: yield TEXT, ''.join(textbuf), textpos del textbuf[:] textpos = None if chunk: try: expr = Expression(chunk.strip(), pos[0], pos[1], lookup=lookup) yield EXPR, expr, tuple(pos) except SyntaxError, err: raise TemplateSyntaxError(err, filepath, pos[1], pos[2] + (err.offset or 0)) else: textbuf.append(chunk) if textpos is None: textpos = tuple(pos) if '\n' in chunk: lines = chunk.splitlines() pos[1] += len(lines) - 1 pos[2] += len(lines[-1]) else: pos[2] += len(chunk) def lex(text, textpos, filepath): offset = pos = 0 end = len(text) escaped = False while 1: if escaped: offset = text.find(PREFIX, offset + 2) escaped = False else: offset = text.find(PREFIX, pos) if offset < 0 or offset == end - 1: break next = text[offset + 1] if next == '{': if offset > pos: yield False, text[pos:offset] pos = offset + 2 level = 1 while level: match = token_re.match(text, pos) if match is None or not match.group(): # if there isn't a match or the match is the empty # string, we're not going to match up braces ever raise TemplateSyntaxError('invalid syntax', filepath, *textpos[1:]) pos = match.end() tstart, tend = match.regs[3] token = text[tstart:tend] if token == '{': level += 1 elif token == '}': level -= 1 yield True, text[offset + 2:pos - 1] elif next in NAMESTART: if offset > pos: yield False, text[pos:offset] pos = offset pos += 1 while pos < end: char = text[pos] if char not in NAMECHARS: break pos += 1 yield True, text[offset + 1:pos].strip() elif not escaped and next == PREFIX: if offset > pos: yield False, text[pos:offset] escaped = True pos = offset + 1 else: yield False, text[pos:offset + 1] pos = offset + 1 if pos < end: yield False, text[pos:]