raise error if passed base is not a zipfile or dir

my/core/structure.py

@@ -118,6 +118,10 @@ def match_structure(
             zf = zipfile.ZipFile(base)
             zf.extractall(path=sd)
 
+        else:
+            if not searchdir.is_dir():
+                raise NotADirectoryError(f"Expected either a zipfile or a directory, received {searchdir}")
+
         matches: List[Path] = []
         possible_targets: List[Path] = [searchdir]
 

tests/core/test_structure.py

@@ -1,7 +1,10 @@
-from my.core.structure import match_structure
+import pytest
 
 from pathlib import Path
 
+from my.core.structure import match_structure
+
+
 structure_data: Path = Path(__file__).parent / "structure_data"
 
 gdpr_expected = ("comments", "messages/index.csv", "profile")
@@ -25,3 +28,10 @@ def test_gdpr_unzip() -> None:
     # make sure the temporary directory this created no longer exists
     assert not extracted.exists()
 
+
+def test_not_directory() -> None:
+    with pytest.raises(NotADirectoryError, match=r"Expected either a zipfile or a directory"):
+        with match_structure(
+            structure_data / "messages/index.csv", expected=gdpr_expected
+        ):
+            pass