Revert regression: escape=True also escapes path separators

Author: shreve

nbgrader/coursedir.py

@@ -310,6 +310,13 @@ def format_path(
         assignment_id: str = '.',
         escape: bool = False
     ) -> str:
+        """
+        Produce an absolute path to an assignment directory.
+
+        When escape=True, the non-passed elements of the path are regex-escaped, so the
+        resulting string can be used as a pattern to match path components.
+        """
+
         kwargs = dict(
             nbgrader_step=nbgrader_step,
             student_id=student_id,
@@ -323,7 +330,10 @@ def format_path(
 
         path = base / self.directory_structure.format(**kwargs)
 
-        return str(path)
+        if escape:
+            return path.anchor + re.escape(os.path.sep).join(path.parts[1:])
+        else:
+            return str(path)
 
     def find_assignments(self,
         nbgrader_step: str = "*",

nbgrader/tests/test_coursedir.py

@@ -20,24 +20,25 @@ def test_coursedir_configurable(conf, course_dir):
     assert coursedir.root == course_dir
 
 
-def test_coursedir_format_path(conf):
+@pytest.mark.parametrize("root", [None, os.path.sep + "[special]~root"])
+def test_coursedir_format_path(conf, root):
+    if root is not None:
+        conf.CourseDirectory.root = root
     coursedir = CourseDirectory(config=conf)
 
-    expected = os.path.join(coursedir.root, "step", "student_id", "assignment_id")
-    assert coursedir.format_path("step", "student_id", "assignment_id") == expected
+    # The default includes the un-escaped root
+    path = os.path.join(coursedir.root, "step", "student_id", "assignment1")
+    assert coursedir.format_path("step", "student_id", "assignment1") == path
 
+    # The escape=True option escapes the root and path separators
     escaped = Path(re.escape(coursedir.root))
-    expected = str(escaped / "step" / "student_id" / "assignment_id")
-    assert coursedir.format_path("step", "student_id", "assignment_id", escape=True) == expected
+    expected = escaped.anchor + re.escape(os.path.sep).join(
+        (escaped / "step" / "student_id" / "(?P<assignment_id>.*)").parts[1:])
 
+    actual = coursedir.format_path("step", "student_id", "(?P<assignment_id>.*)", escape=True)
+    assert actual == expected
 
-def test_coursedir_format_path_with_specials(conf):
-    conf.CourseDirectory.root = "/[test] root"
-    coursedir = CourseDirectory(config=conf)
-
-    expected = os.path.join("/[test] root", "step", "student_id", "assignment_id")
-    assert coursedir.format_path("step", "student_id", "assignment_id") == expected
-
-    escaped = Path(re.escape(coursedir.root))
-    expected = str(escaped / "step" / "student_id" / "assignment_id")
-    assert coursedir.format_path("step", "student_id", "assignment_id", escape=True) == expected
+    # The escape=True option produces a regex pattern which can match paths
+    match = re.match(actual, path)
+    assert match is not None
+    assert match.group("assignment_id") == "assignment1"