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Diffstat (limited to 'genshi/template/interpolation.py')
| -rw-r--r-- | genshi/template/interpolation.py | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/genshi/template/interpolation.py b/genshi/template/interpolation.py new file mode 100644 index 0000000..1e1a385 --- /dev/null +++ b/genshi/template/interpolation.py @@ -0,0 +1,153 @@ +# -*- 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: + 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:] |