Django template tag that allows inline code.

code.py

"""
Add {% code %}{% endcode %} tags to template.

Note: it will only run if it is in a block that is rendered.
"""

from __future__ import absolute_import, division, print_function, unicode_literals

import re
import sys
import traceback

from django import template
from django.template.base import TemplateSyntaxError, Token


register = template.Library()


indent_re = re.compile('^\n*([ \t]*)[^ \t]')
line_re = re.compile('^.*$', re.MULTILINE)


@register.tag
def code(parser, token):
    # read source
    nodelist = parser.parse('endpython')
    if nodelist.contains_nontext:
        raise TemplateSyntaxError('Python block must only contain text.')
    parser.delete_first_token()
    source = nodelist.render(None)

    # get indent
    try:
        indent = len(indent_re.match(source).group(1))
    except AttributeError:  # No match
        indent = 0

    # fix indent, compile and return node
    source = '\n'.join(line.group()[indent:] for line in line_re.finditer(source))
    code = compile(source, parser.origin.name, 'exec')
    return CodeNode(code)


class CodeNode(template.Node):
    def __init__(self, code):
        self.code = code

    def render(self, context):
        exec self.code

    def render_annotated(self, context):
        try:
            return self.render(context)
        except Exception as e:
            if context.template.engine.debug and not hasattr(e, 'template_debug'):
                e.template_debug = self.get_exception_info(context, e)
            raise

    def get_exception_info(self, context, e):
        tb = sys.exc_info()[2]
        print(traceback.extract_tb(tb)[-1])
        lineno = traceback.extract_tb(tb)[-1][1] - 1
        del tb
        code_start = self.token.position[1]

        for i, line in enumerate(line_re.finditer(context.template.source[code_start:])):
            if i == lineno:
                start, end = line.span()
                start += code_start
                end += code_start
                break

        return context.template.get_exception_info(e, Token(None, None, position=(start, end)))