Load templates (even included & extended templates) based on Mezzanine HOST_THEME

host_template_loader.py

import os
import sys
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.template.base import TemplateDoesNotExist
from django.template.loaders.app_directories import Loader as BaseLoader
from django.utils._os import safe_join
from django.utils.importlib import import_module
from django.utils import six
from mezzanine.core.request import current_request

try:
    from collections import OrderedDict
except ImportError:
    from django.utils.datastructures import SortedDict as OrderedDict

# Copied from django.template.loaders.app_directories
# At compile time, cache the directories to search.
def get_template_dir(app):
    try:
        mod = import_module(app)
    except ImportError as e:
        raise ImproperlyConfigured('ImportError %s: %s' % (app, e.args[0]))
    template_dir = os.path.join(os.path.dirname(mod.__file__), 'templates')
    if os.path.isdir(template_dir):
        if six.PY2:
            template_dir = template_dir.decode(fs_encoding)
        return template_dir

if six.PY2:
    fs_encoding = sys.getfilesystemencoding() or sys.getdefaultencoding()
app_template_dirs = tuple(filter(os.path.isdir, filter(None, map(get_template_dir, settings.INSTALLED_APPS))))

class Loader(BaseLoader):
    is_usable = True

    def get_template_sources(self, template_name, template_dirs=None):
        HOST_THEMES = getattr(settings, 'HOST_THEMES', None)
        if not HOST_THEMES:
            return

        HOST_THEMES = OrderedDict(HOST_THEMES)

        assert len(HOST_THEMES) >= 1, "There should be at least one item defined in HOST_THEMES"

        host_name = current_request().get_host().split(':')[0].lower()
        if host_name not in HOST_THEMES:
            return

        host_template_dir = get_template_dir(HOST_THEMES[host_name])

        if not template_dirs:
            template_dirs = app_template_dirs

        # Here is the magic: we add the path of the host theme before any other app
        template_dirs = (host_template_dir,) + template_dirs
        for template_dir in super(Loader, self).get_template_sources(template_name, template_dirs):
            yield template_dir

settings.py

# `host_template_loader` needs to be the 1st entry in `TEMPLATE_LOADERS`
TEMPLATE_LOADERS = (
    "host_template_loader.Loader",
    "django.template.loaders.filesystem.Loader",
    "django.template.loaders.app_directories.Loader",
)

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',

    'host_theme',

    # You need to add the theme apps in `INSTALLED_APPS`
    'english',
    'arabic',

)

# Now you can set `HOST_THEMES` as usual
HOST_THEMES = (
    # Host URL, Host theme app
    ('ar.localtest.me', 'arabic'),
    ('en.localtest.me', 'english'),
)