Raise error for Dataset.open() if dataset is not found. (#1246)

* Raise error for Dataset.open() if dataset is not found.

* Update changelog.

* Move path validation to Dataset.open()

Author: markbader

webknossos/Changelog.md

@@ -19,6 +19,7 @@ For upgrade instructions, please check the respective _Breaking Changes_ section
 ### Changed
 
 ### Fixed
+- Fixed a misleading error message when Dataset.open() can't find a valid dataset. [#1246](https://github.com/scalableminds/webknossos-libs/pull/1246)
 
 
 ## [0.16.6](https://github.com/scalableminds/webknossos-libs/releases/tag/v0.16.6) - 2025-02-03
@@ -39,7 +40,6 @@ For upgrade instructions, please check the respective _Breaking Changes_ section
 - Fixed a bug with loading metadata lists. [#1247](https://github.com/scalableminds/webknossos-libs/pull/1247)
 
 
-
 ## [0.16.4](https://github.com/scalableminds/webknossos-libs/releases/tag/v0.16.4) - 2025-01-23
 [Commits](https://github.com/scalableminds/webknossos-libs/compare/v0.16.3...v0.16.4)
 
@@ -70,7 +70,6 @@ For upgrade instructions, please check the respective _Breaking Changes_ section
 - Fixed an issue when shallow copying datasets with a remote mag. [#1224](https://github.com/scalableminds/webknossos-libs/pull/1224)
 
 
-
 ## [0.16.2](https://github.com/scalableminds/webknossos-libs/releases/tag/v0.16.2) - 2024-12-18
 [Commits](https://github.com/scalableminds/webknossos-libs/compare/v0.16.1...v0.16.2)
 

webknossos/tests/dataset/test_dataset.py

@@ -2802,3 +2802,8 @@ def test_remote_dataset_urls() -> None:
         f"http://localhost:9000/datasets/l4_sample-{dataset_id}/view#2786,4326,1816,0,3"
     )
     assert ds6.url == ds.url
+
+
+def test_dataset_open_wrong_path() -> None:
+    with pytest.raises(FileNotFoundError):
+        Dataset.open("wrong_path")

webknossos/webknossos/dataset/dataset.py

@@ -467,10 +467,16 @@ def open(cls, dataset_path: Union[str, PathLike]) -> "Dataset":
 
         The `dataset_path` refers to the top level directory of the dataset (excluding layer or magnification names).
         """
-        return cls(
-            dataset_path,
-            voxel_size_with_unit=_UNSPECIFIED_SCALE_FROM_OPEN,
-            exist_ok=True,
+        if (
+            path := strip_trailing_slash(UPath(dataset_path)) / PROPERTIES_FILE_NAME
+        ).exists():
+            return cls(
+                dataset_path,
+                voxel_size_with_unit=_UNSPECIFIED_SCALE_FROM_OPEN,
+                exist_ok=True,
+            )
+        raise FileNotFoundError(
+            f"Could not find a valid `datasource-properties.json` file at {path}."
         )
 
     @classmethod