Django command for getting info about template tags and filters within your project

tag_info.py

# coding: utf-8
'''Django command for getting info about template tags and filters within your project

It suports two output formats: human readable (with extra doc) and vim quickfix format

Usage: ./manage.py tag_info tag_or_filter_name
'''

import os
import sys
from optparse import make_option
import inspect
import textwrap

from django.core.management.base import BaseCommand, CommandError
from django.template import get_templatetags_modules, get_library, InvalidTemplateLibrary, builtins
from django.utils.importlib import import_module

FORMATS = {
    'vim': '{path}:{line}:{name}',
    'human': '{name} in line {line} of {path}',
}

class Command(BaseCommand):
    help = 'Show all signals receivers'
    option_list = BaseCommand.option_list + (
        make_option('--format',
            dest='line_format',
            default='human',
            choices=FORMATS.keys(),
            help='Line format (available choices: {0})'.format(', '.join(FORMATS)),
        ),
        make_option('--show-doc',
            action='store_true',
            dest='show_doc',
            help='Show docstring for found tag or filter, if --format=human (default: False)',
        ),
    )
    def handle(self, name, *args, **options):
        line_format = options['line_format']
        show_doc = options['show_doc']
        if line_format not in FORMATS:
            raise CommandError('format must be on of {0}, not {1}'.format(line_format, FORMATS.keys()))
        msg = FORMATS[line_format]

        libraries = set(builtins[:])
        for module in set(get_templatetags_modules()):
            templatetags_module = import_module(module)
            files = os.listdir(os.path.dirname(templatetags_module.__file__))
            lib_names = [lib_name for lib_name, ext in map(os.path.splitext, files) if ext == '.py' and not lib_name.startswith('_')]
            for lib_name in lib_names:
                try:
                    libraries.add(get_library(lib_name))
                except InvalidTemplateLibrary:
                    pass

        def print_info(obj):
            # Here be dragons
            # 
            # Very strange Python and Django magic: `inclusion_tag` and
            # `simple_tag` returns curried function named `generic_tag_compiler`
            # that has Node as it fourth arg and Node has `render` method with
            # free variables containing our original functions
            # 
            # After that knowledge other is very easy but lil’ tricky
            template = None
            if obj.func_name == '_curried':
                cls = obj.func_closure[0].cell_contents[3]
                # It evaluates to string for inslusion_tag
                template = cls.render.im_func.func_closure[0].cell_contents
                orig = cls.render.im_func.func_closure[1].cell_contents
                obj = orig

                # import ipdb; ipdb.set_trace()

            if line_format == 'human' and show_doc:
                args, varargs, keywords, defaults = inspect.getargspec(obj)
                doc = inspect.getdoc(obj)

                spec = []
                if args:
                    if defaults:
                        spec.append(', '.join(args[:len(defaults)]))
                        spec.append(', '.join('{0}={1!r}'.format(key, value) for key, value in zip(args[len(defaults):], defaults)))
                    else:
                        spec.append(', '.join(args))
                if varargs:
                    spec.append('*' + varargs)
                if keywords:
                    spec.append('**' + keywords)

                print '{name}({spec})'.format(name=obj.func_name, spec=', '.join(spec)),
                if template:
                    print '- decorated by inclusion_tag("{template}")'.format(template=template)
                else:
                    print

                print '    # Line {line} of {path}'.format(name=obj.func_name, line=inspect.getsourcelines(obj)[1], path=inspect.getsourcefile(obj))
                if doc:
                    for line in doc.splitlines():
                        print '    ' + line
            else:
                print msg.format(name=obj.func_name, line=inspect.getsourcelines(obj)[1], path=inspect.getsourcefile(obj))

        for lib in libraries:
            if name in lib.tags:
                print_info(lib.tags[name])
            if name in lib.filters:
                print_info(lib.filters[name])