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from django.core.exceptions import ImproperlyConfigured
from django.utils import lru_cache, six
from django.utils.functional import cached_property
from django.utils.module_loading import import_string
from .base import Context, Template
from .context import _builtin_context_processors
from .exceptions import TemplateDoesNotExist
from .library import import_library
class Engine(object):
default_builtins = [
'django.template.defaulttags',
'django.template.defaultfilters',
'django.template.loader_tags',
]
def __init__(self, dirs=None, app_dirs=False, context_processors=None,
debug=False, loaders=None, string_if_invalid='',
file_charset='utf-8', libraries=None, builtins=None):
if dirs is None:
dirs = []
if context_processors is None:
context_processors = []
if loaders is None:
loaders = ['django.template.loaders.filesystem.Loader']
if app_dirs:
loaders += ['django.template.loaders.app_directories.Loader']
else:
if app_dirs:
raise ImproperlyConfigured(
"app_dirs must not be set when loaders is defined.")
if libraries is None:
libraries = {}
if builtins is None:
builtins = []
self.dirs = dirs
self.app_dirs = app_dirs
self.context_processors = context_processors
self.debug = debug
self.loaders = loaders
self.string_if_invalid = string_if_invalid
self.file_charset = file_charset
self.libraries = libraries
self.template_libraries = self.get_template_libraries(libraries)
self.builtins = self.default_builtins + builtins
self.template_builtins = self.get_template_builtins(self.builtins)
@staticmethod
@lru_cache.lru_cache()
def get_default():
"""
When only one DjangoTemplates backend is configured, returns it.
Raises ImproperlyConfigured otherwise.
This is required for preserving historical APIs that rely on a
globally available, implicitly configured engine such as:
>>> from django.template import Context, Template
>>> template = Template("Hello {{ name }}!")
>>> context = Context({'name': "world"})
>>> template.render(context)
'Hello world!'
"""
# Since Engine is imported in django.template and since
# DjangoTemplates is a wrapper around this Engine class,
# local imports are required to avoid import loops.
from django.template import engines
from django.template.backends.django import DjangoTemplates
django_engines = [engine for engine in engines.all()
if isinstance(engine, DjangoTemplates)]
if len(django_engines) == 1:
# Unwrap the Engine instance inside DjangoTemplates
return django_engines[0].engine
elif len(django_engines) == 0:
raise ImproperlyConfigured(
"No DjangoTemplates backend is configured.")
else:
raise ImproperlyConfigured(
"Several DjangoTemplates backends are configured. "
"You must select one explicitly.")
@cached_property
def template_context_processors(self):
context_processors = _builtin_context_processors
context_processors += tuple(self.context_processors)
return tuple(import_string(path) for path in context_processors)
def get_template_builtins(self, builtins):
return [import_library(x) for x in builtins]
def get_template_libraries(self, libraries):
loaded = {}
for name, path in libraries.items():
loaded[name] = import_library(path)
return loaded
@cached_property
def template_loaders(self):
return self.get_template_loaders(self.loaders)
def get_template_loaders(self, template_loaders):
loaders = []
for template_loader in template_loaders:
loader = self.find_template_loader(template_loader)
if loader is not None:
loaders.append(loader)
return loaders
def find_template_loader(self, loader):
if isinstance(loader, (tuple, list)):
args = list(loader[1:])
loader = loader[0]
else:
args = []
if isinstance(loader, six.string_types):
loader_class = import_string(loader)
return loader_class(self, *args)
else:
raise ImproperlyConfigured(
"Invalid value in template loaders configuration: %r" % loader)
def find_template(self, name, dirs=None, skip=None):
tried = []
for loader in self.template_loaders:
if loader.supports_recursion:
try:
template = loader.get_template(
name, template_dirs=dirs, skip=skip,
)
return template, template.origin
except TemplateDoesNotExist as e:
tried.extend(e.tried)
else:
# RemovedInDjango20Warning: Use old api for non-recursive
# loaders.
try:
return loader(name, dirs)
except TemplateDoesNotExist:
pass
raise TemplateDoesNotExist(name, tried=tried)
def from_string(self, template_code):
"""
Returns a compiled Template object for the given template code,
handling template inheritance recursively.
"""
return Template(template_code, engine=self)
def get_template(self, template_name):
"""
Returns a compiled Template object for the given template name,
handling template inheritance recursively.
"""
template, origin = self.find_template(template_name)
if not hasattr(template, 'render'):
# template needs to be compiled
template = Template(template, origin, template_name, engine=self)
return template
def render_to_string(self, template_name, context=None):
"""
Render the template specified by template_name with the given context.
For use in Django's test suite.
"""
if isinstance(template_name, (list, tuple)):
t = self.select_template(template_name)
else:
t = self.get_template(template_name)
# Django < 1.8 accepted a Context in `context` even though that's
# unintended. Preserve this ability but don't rewrap `context`.
if isinstance(context, Context):
return t.render(context)
else:
return t.render(Context(context))
def select_template(self, template_name_list):
"""
Given a list of template names, returns the first that can be loaded.
"""
if not template_name_list:
raise TemplateDoesNotExist("No template names provided")
not_found = []
for template_name in template_name_list:
try:
return self.get_template(template_name)
except TemplateDoesNotExist as exc:
if exc.args[0] not in not_found:
not_found.append(exc.args[0])
continue
# If we get here, none of the templates could be loaded
raise TemplateDoesNotExist(', '.join(not_found))
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