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- from django.core.exceptions import (
- ImproperlyConfigured, SuspiciousFileOperation,
- )
- from django.template.utils import get_app_template_dirs
- from django.utils._os import safe_join
- from django.utils.functional import cached_property
-
-
- class BaseEngine:
-
- # Core methods: engines have to provide their own implementation
- # (except for from_string which is optional).
-
- def __init__(self, params):
- """
- Initialize the template engine.
-
- `params` is a dict of configuration settings.
- """
- params = params.copy()
- self.name = params.pop('NAME')
- self.dirs = list(params.pop('DIRS'))
- self.app_dirs = params.pop('APP_DIRS')
- if params:
- raise ImproperlyConfigured(
- "Unknown parameters: {}".format(", ".join(params)))
-
- @property
- def app_dirname(self):
- raise ImproperlyConfigured(
- "{} doesn't support loading templates from installed "
- "applications.".format(self.__class__.__name__))
-
- def from_string(self, template_code):
- """
- Create and return a template for the given source code.
-
- This method is optional.
- """
- raise NotImplementedError(
- "subclasses of BaseEngine should provide "
- "a from_string() method")
-
- def get_template(self, template_name):
- """
- Load and return a template for the given name.
-
- Raise TemplateDoesNotExist if no such template exists.
- """
- raise NotImplementedError(
- "subclasses of BaseEngine must provide "
- "a get_template() method")
-
- # Utility methods: they are provided to minimize code duplication and
- # security issues in third-party backends.
-
- @cached_property
- def template_dirs(self):
- """
- Return a list of directories to search for templates.
- """
- # Immutable return value because it's cached and shared by callers.
- template_dirs = tuple(self.dirs)
- if self.app_dirs:
- template_dirs += get_app_template_dirs(self.app_dirname)
- return template_dirs
-
- def iter_template_filenames(self, template_name):
- """
- Iterate over candidate files for template_name.
-
- Ignore files that don't lie inside configured template dirs to avoid
- directory traversal attacks.
- """
- for template_dir in self.template_dirs:
- try:
- yield safe_join(template_dir, template_name)
- except SuspiciousFileOperation:
- # The joined path was located outside of this template_dir
- # (it might be inside another one, so this isn't fatal).
- pass
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