[BUGFIX] Fix overrides failing validation in datetime vars (#209)

src/ytdl_sub/validators/string_datetime.py

@@ -22,7 +22,7 @@ class StringDatetimeValidator(OverridesStringFormatterValidator):
     def apply_formatter(self, variable_dict: Dict[str, str]) -> str:
         output = super().apply_formatter(variable_dict)
         try:
-            _ = datetime_from_str(self._value)
+            _ = datetime_from_str(output)
         except Exception as exc:
             raise self._validation_exception(f"Invalid datetime string: {str(exc)}")
         return output

tests/unit/config/test_preset.py

@@ -135,6 +135,24 @@ class TestPreset:
             "key-3": "this-preset",
         }
 
+    def test_preset_datetime_with_override(self, config_file, youtube_video, output_options):
+        preset = Preset(
+            config=config_file,
+            name="test",
+            value={
+                "youtube": youtube_video,
+                "output_options": dict(
+                    output_options,
+                    **{"maintain_download_archive": True, "keep_files_after": "today-{ttl}"}
+                ),
+                "overrides": {"ttl": "2months"},
+            },
+        )
+        assert (
+            preset.overrides.apply_formatter(formatter=preset.output_options.keep_files_after)
+            == "today-2months"
+        )
+
     @pytest.mark.parametrize(
         "parent_preset", ["preset_self_loop", "preset_loop_0", "preset_loop_1"]
     )