literal.py

from django.template import Parser, Lexer, Token, Context, TextNode, TOKEN_BLOCK, TOKEN_COMMENT, TOKEN_TEXT, TOKEN_VAR
from django.conf import settings

LITERAL_DELIMITER = '8====D'

class LiteralNode(TextNode):
    pass

def parse(parser):
    depth = 0
    while parser.tokens:
        token = parser.next_token()
        if token.token_type == TOKEN_BLOCK:
            if token.contents == 'literal':
                depth += 1
            elif token.contents == 'endliteral':
                depth -= 1
        if depth < 0:
            break
        yield token
    if not parser.tokens and depth >= 0:
        parser.unclosed_block_tag(('endliteral',))

def do_literal(parser, token):
    literal = ''.join({
        TOKEN_BLOCK: '{%% %s %%}',
        TOKEN_VAR: '{{ %s }}',
        TOKEN_COMMENT: '{# %s #}',
        TOKEN_TEXT: '%s',
    }[token.token_type] % token.contents for token in parse(parser))
    literal = '%s%s%s' % (LITERAL_DELIMITER, literal, LITERAL_DELIMITER)
    return LiteralNode(literal)

def first_pass(data):
    lexer = Lexer(data, None)
    parser = Parser(lexer.tokenize())
    parser.tags['literal'] = do_literal
    context = Context({'a_var': 'foo!'})
    nodes = parser.parse()
    rendered = ''.join(node.render(context) for node in nodes)
    return rendered

def second_pass(data):
    bits = data.split(LITERAL_DELIMITER)
    parser = Parser([])
    context = Context({'a_var': 'foo!'})
    for index, bit in enumerate(bits):
        if index % 2:
            parser.tokens += Lexer(bit, None).tokenize()
        else:
            parser.tokens.append(Token( TOKEN_TEXT, bit))
    nodes = parser.parse()
    rendered = ''.join(node.render(context) for node in nodes)
    return rendered

if __name__ == '__main__':
    data = """
        before
        {{ a_var }}

        {% templatetag openblock %} scary UGC hack {% templatetag closeblock %}
        {% literal %}
            {% if 1 %}
                this is literal
                {# comment #}
                {{ a_var|upper }}
            {% endif %}
        {% endliteral %}

        between

        {% literal %}
            second literal bit
            {{ a_var }}
        {% endliteral %}

        after
        """
    settings.configure()
    pass1 = first_pass(data)
    pass2 = second_pass(pass1)
    print '=======AFTER PASS1========'
    print pass1
    print '=======AFTER PASS2========'
    print pass2