normpath on final template filename

CHANGES.rst

@@ -5,6 +5,9 @@ Version 3.1.1
 
 Unreleased
 
+-   The template filename on Windows uses the primary path separator.
+    :issue:`1637`
+
 
 Version 3.1.0
 -------------

src/jinja2/loaders.py

@@ -3,6 +3,7 @@
 """
 import importlib.util
 import os
+import pathlib
 import posixpath
 import sys
 import typing as t
@@ -213,7 +214,8 @@ def uptodate() -> bool:
                 except OSError:
                     return False
 
-            return contents, filename, uptodate
+            # Use normpath to convert Windows altsep to sep.
+            return contents, os.path.normpath(filename), uptodate
         raise TemplateNotFound(template)
 
     def list_templates(self) -> t.List[str]:
@@ -330,8 +332,11 @@ def get_source(
         self, environment: "Environment", template: str
     ) -> t.Tuple[str, str, t.Optional[t.Callable[[], bool]]]:
         # Use posixpath even on Windows to avoid "drive:" or UNC
-        # segments breaking out of the search directory.
-        p = posixpath.join(self._template_root, *split_template_path(template))
+        # segments breaking out of the search directory. Use normpath to
+        # convert Windows altsep to sep.
+        p = os.path.normpath(
+            posixpath.join(self._template_root, *split_template_path(template))
+        )
         up_to_date: t.Optional[t.Callable[[], bool]]
 
         if self._archive is None:

tests/test_loader.py

@@ -172,6 +172,15 @@ def test_uses_specified_encoding(self, encoding, expect):
         t = e.get_template("mojibake.txt")
         assert t.render() == expect
 
+    def test_filename_normpath(self):
+        """Nested template names should only contain ``os.sep`` in the
+        loaded filename.
+        """
+        loader = loaders.FileSystemLoader(self.searchpath)
+        e = Environment(loader=loader)
+        t = e.get_template("foo/test.html")
+        assert t.filename == str(self.searchpath / "foo" / "test.html")
+
 
 class TestModuleLoader:
     archive = None