Source code for django.template.engine
import functools
from django.core.exceptions import ImproperlyConfigured
from django.utils.functional import cached_property
from django.utils.module_loading import import_string
from .base import Template
from .context import Context, _builtin_context_processors
from .exceptions import TemplateDoesNotExist
from .library import import_library
[docs]
class Engine:
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,
autoescape=True,
):
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"]
loaders = [("django.template.loaders.cached.Loader", loaders)]
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.autoescape = autoescape
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)
def __repr__(self):
return (
"<%s:%s app_dirs=%s%s debug=%s loaders=%s string_if_invalid=%s "
"file_charset=%s%s%s autoescape=%s>"
) % (
self.__class__.__qualname__,
"" if not self.dirs else " dirs=%s" % repr(self.dirs),
self.app_dirs,
(
""
if not self.context_processors
else " context_processors=%s" % repr(self.context_processors)
),
self.debug,
repr(self.loaders),
repr(self.string_if_invalid),
repr(self.file_charset),
"" if not self.libraries else " libraries=%s" % repr(self.libraries),
"" if not self.builtins else " builtins=%s" % repr(self.builtins),
repr(self.autoescape),
)
[docs]
@staticmethod
@functools.lru_cache
def get_default():
"""
Return the first DjangoTemplates backend that's configured, or raise
ImproperlyConfigured if none are configured.
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
for engine in engines.all():
if isinstance(engine, DjangoTemplates):
return engine.engine
raise ImproperlyConfigured("No DjangoTemplates backend is configured.")
@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)):
loader, *args = loader
else:
args = []
if isinstance(loader, str):
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:
try:
template = loader.get_template(name, skip=skip)
return template, template.origin
except TemplateDoesNotExist as e:
tried.extend(e.tried)
raise TemplateDoesNotExist(name, tried=tried)
[docs]
def from_string(self, template_code):
"""
Return a compiled Template object for the given template code,
handling template inheritance recursively.
"""
return Template(template_code, engine=self)
[docs]
def get_template(self, template_name):
"""
Return 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, autoescape=self.autoescape))
[docs]
def select_template(self, template_name_list):
"""
Given a list of template names, return 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))
