check folder structure for correct format

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - fix: use a-z for sms mfa index to disambiguate with mfa code with leading zeros [#925](https://github.com/icloud-photos-downloader/icloud_photos_downloader/issues/925)
+- fix: report proper error on bad `--folder-structure` value [#937](https://github.com/icloud-photos-downloader/icloud_photos_downloader/issues/937)
 
 ## 1.23.0 (2024-07-25)
 

src/icloudpd/base.py

@@ -671,6 +671,13 @@ def main(
             print("Webui must be the last --password-provider")
             sys.exit(2)
 
+        if folder_structure != "none":
+            try:
+                folder_structure.format(datetime.datetime.now())
+            except:  # noqa E722
+                print("Format specified in --folder-structure is incorrect")
+                sys.exit(2)
+
         status_exchange = StatusExchange()
         config = Config(
             directory=directory,

tests/test_folder_structure.py

@@ -209,3 +209,38 @@ def test_folder_structure_de_posix(self) -> None:
             assert os.path.exists(
                 os.path.join(data_dir, os.path.normpath(file_name))
             ), f"File {file_name} expected, but does not exist"
+
+    def test_folder_structure_bad_format(self) -> None:
+        base_dir = os.path.join(self.fixtures_path, inspect.stack()[0][3])
+
+        files_to_create: List[Tuple[str, str, int]] = []
+        files_to_download: List[Tuple[str, str]] = []
+
+        # Note - This test uses the same cassette as test_download_photos.py
+        data_dir, result = run_icloudpd_test(
+            self.assertEqual,
+            self.vcr_path,
+            base_dir,
+            "listing_photos.yml",
+            files_to_create,
+            files_to_download,
+            [
+                "--username",
+                "[email protected]",
+                "--password",
+                "password1",
+                "--recent",
+                "5",
+                "--only-print-filenames",
+                "--folder-structure={%Y}{%Y}",
+                "--no-progress-bar",
+                "--threads-num",
+                "1",
+            ],
+        )
+
+        assert result.exit_code == 2
+
+        messages = result.output.splitlines()
+
+        self.assertTrue("Format specified in --folder-structure is incorrect" in messages)