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import os
from collections import Counter, OrderedDict
from django.apps import apps
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.utils import lru_cache
from django.utils._os import upath
from django.utils.functional import cached_property
from django.utils.module_loading import import_string
class InvalidTemplateEngineError(ImproperlyConfigured):
pass
class EngineHandler(object):
def __init__(self, templates=None):
"""
templates is an optional list of template engine definitions
(structured like settings.TEMPLATES).
"""
self._templates = templates
self._engines = {}
@cached_property
def templates(self):
if self._templates is None:
self._templates = settings.TEMPLATES
templates = OrderedDict()
backend_names = []
for tpl in self._templates:
tpl = tpl.copy()
try:
# This will raise an exception if 'BACKEND' doesn't exist or
# isn't a string containing at least one dot.
default_name = tpl['BACKEND'].rsplit('.', 2)[-2]
except Exception:
invalid_backend = tpl.get('BACKEND', '<not defined>')
raise ImproperlyConfigured(
"Invalid BACKEND for a template engine: {}. Check "
"your TEMPLATES setting.".format(invalid_backend))
tpl.setdefault('NAME', default_name)
tpl.setdefault('DIRS', [])
tpl.setdefault('APP_DIRS', False)
tpl.setdefault('OPTIONS', {})
templates[tpl['NAME']] = tpl
backend_names.append(tpl['NAME'])
counts = Counter(backend_names)
duplicates = [alias for alias, count in counts.most_common() if count > 1]
if duplicates:
raise ImproperlyConfigured(
"Template engine aliases aren't unique, duplicates: {}. "
"Set a unique NAME for each engine in settings.TEMPLATES."
.format(", ".join(duplicates)))
return templates
def __getitem__(self, alias):
try:
return self._engines[alias]
except KeyError:
try:
params = self.templates[alias]
except KeyError:
raise InvalidTemplateEngineError(
"Could not find config for '{}' "
"in settings.TEMPLATES".format(alias))
# If importing or initializing the backend raises an exception,
# self._engines[alias] isn't set and this code may get executed
# again, so we must preserve the original params. See #24265.
params = params.copy()
backend = params.pop('BACKEND')
engine_cls = import_string(backend)
engine = engine_cls(params)
self._engines[alias] = engine
return engine
def __iter__(self):
return iter(self.templates)
def all(self):
return [self[alias] for alias in self]
@lru_cache.lru_cache()
def get_app_template_dirs(dirname):
"""
Return an iterable of paths of directories to load app templates from.
dirname is the name of the subdirectory containing templates inside
installed applications.
"""
template_dirs = []
for app_config in apps.get_app_configs():
if not app_config.path:
continue
template_dir = os.path.join(app_config.path, dirname)
if os.path.isdir(template_dir):
template_dirs.append(upath(template_dir))
# Immutable return value because it will be cached and shared by callers.
return tuple(template_dirs)
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