first comit

venv/lib/python3.10/site-packages/django/template/backends/base.py

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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