--- contrib/python/Jinja2/py3/jinja2/loaders.py	(index)
+++ contrib/python/Jinja2/py3/jinja2/loaders.py	(working tree)
@@ -5,6 +5,7 @@ sources.
 import os
 import posixpath
 import sys
+import pkgutil
 import typing as t
 import weakref
 import zipimport
@@ -21,6 +22,8 @@ if t.TYPE_CHECKING:
     from .environment import Environment
     from .environment import Template
 
+import __res as arcadia_res
+
 
 def split_template_path(template: str) -> t.List[str]:
     """Split a path into segments and perform a sanity check.  If it detects
@@ -288,19 +291,22 @@ class PackageLoader(BaseLoader):
 
         # Make sure the package exists. This also makes namespace
         # packages work, otherwise get_loader returns None.
-        import_module(package_name)
+        package = import_module(package_name)
         spec = importlib.util.find_spec(package_name)
         assert spec is not None, "An import spec was not found for the package."
         loader = spec.loader
         assert loader is not None, "A loader was not found for the package."
         self._loader = loader
         self._archive = None
+        self._package = package
         template_root = None
 
         if isinstance(loader, zipimport.zipimporter):
             self._archive = loader.archive
             pkgdir = next(iter(spec.submodule_search_locations))  # type: ignore
             template_root = os.path.join(pkgdir, package_path).rstrip(os.path.sep)
+        elif hasattr(loader, "arcadia_source_finder"):
+            template_root = os.path.dirname(package.__file__).rstrip(os.path.sep)
         else:
             roots: t.List[str] = []
 
@@ -338,7 +341,16 @@ class PackageLoader(BaseLoader):
         p = posixpath.join(self._template_root, *split_template_path(template))
         up_to_date: t.Optional[t.Callable[[], bool]]
 
-        if self._archive is None:
+        if self._archive is None and hasattr(self, "_package"):
+            try:
+                source = pkgutil.get_data(self.package_name, os.path.join(self.package_path, *split_template_path(template)))
+            except OSError:
+                raise TemplateNotFound(template)
+
+            def up_to_date() -> bool:
+                return True
+
+        elif self._archive is None:
             # Package is a directory.
             if not os.path.isfile(p):
                 raise TemplateNotFound(template)
@@ -368,7 +380,12 @@ class PackageLoader(BaseLoader):
     def list_templates(self) -> t.List[str]:
         results: t.List[str] = []
 
-        if self._archive is None:
+        if self._archive is None and hasattr(self, "_package"):
+            prefix = os.path.join(self._template_root, self.package_path).encode() + b"/"
+            for name in arcadia_res.resfs_files(prefix):
+                results.append(name.removeprefix(prefix).decode())
+
+        elif self._archive is None:
             # Package is a directory.
             offset = len(self._template_root)
 
--- contrib/python/Jinja2/py3/jinja2/loaders.py	(index)
+++ contrib/python/Jinja2/py3/jinja2/loaders.py	(working tree)
@@ -279,6 +279,7 @@ class PackageLoader(BaseLoader):
         package_name: str,
         package_path: "str" = "templates",
         encoding: str = "utf-8",
+        skip_unknown_package: bool = False,
     ) -> None:
         package_path = os.path.normpath(package_path).rstrip(os.path.sep)
 
@@ -291,6 +292,7 @@ class PackageLoader(BaseLoader):
         self.package_path = package_path
         self.package_name = package_name
         self.encoding = encoding
+        self.skip_unknown_package = skip_unknown_package
 
         # Make sure the package exists. This also makes namespace
         # packages work, otherwise get_loader returns None.
@@ -339,6 +341,9 @@ class PackageLoader(BaseLoader):
     def get_source(
         self, environment: "Environment", template: str
     ) -> t.Tuple[str, str, t.Optional[t.Callable[[], bool]]]:
+        if self._template_root is None and self.skip_unknown_package:
+            raise TemplateNotFound(template)
+
         # Use posixpath even on Windows to avoid "drive:" or UNC
         # segments breaking out of the search directory. Use normpath to
         # convert Windows altsep to sep.
@@ -386,6 +391,9 @@ class PackageLoader(BaseLoader):
     def list_templates(self) -> t.List[str]:
         results: t.List[str] = []
 
+        if self._template_root is None and self.skip_unknown_package:
+            return results
+
         if self._archive is None and hasattr(self, "_package"):
             prefix = os.path.join(self._template_root, self.package_path).encode() + b"/"
             for name in arcadia_res.resfs_files(prefix):
--- contrib/python/Jinja2/py3/jinja2/loaders.py	(index)
+++ contrib/python/Jinja2/py3/jinja2/loaders.py	(working tree)
@@ -296,7 +296,13 @@ class PackageLoader(BaseLoader):
 
         # Make sure the package exists. This also makes namespace
         # packages work, otherwise get_loader returns None.
-        package = import_module(package_name)
+        try:
+            package = import_module(package_name)
+        except ModuleNotFoundError:
+            if skip_unknown_package:
+                self._template_root = None
+                return
+            raise
         spec = importlib.util.find_spec(package_name)
         assert spec is not None, "An import spec was not found for the package."
         loader = spec.loader