Fix _dump_mag_path with paths of different file systems (#1298)

* Only check for relative path on same file system

* Write changelog

* Extract into utils function

Author: Tobias314

webknossos/Changelog.md

@@ -20,6 +20,7 @@ For upgrade instructions, please check the respective _Breaking Changes_ section
 
 ### Fixed
 - Fixed an issue with `Dataset.get_remote_datasets()` that causes value lookups to fail. [#1286](https://github.com/scalableminds/webknossos-libs/pull/1286)
+- Fixed issue with adding remote mags to local dataset due to some UPath checks failing for paths from different file systems. [#1298](https://github.com/scalableminds/webknossos-libs/pull/1298)
 
 
 ## [2.3.2](https://github.com/scalableminds/webknossos-libs/releases/tag/v2.3.2) - 2025-04-25

webknossos/webknossos/dataset/layer.py

@@ -53,6 +53,7 @@
     named_partial,
     resolve_if_fs_path,
     rmtree,
+    safe_is_relative_to,
     warn_deprecated,
 )
 from .defaults import (
@@ -230,7 +231,7 @@ def _dump_mag_path(path: Path, dataset_path: Path) -> str:
     path = resolve_if_fs_path(path)
     if str(path).startswith(str(dataset_path)):
         return str(path).removeprefix(str(dataset_path)).lstrip("/")
-    if path.is_relative_to(dataset_path):
+    if safe_is_relative_to(path, dataset_path):
         return str(path.relative_to(dataset_path))
     if isinstance(path, UPath) and path.protocol == "s3":
         return f"s3://{urlparse(path.storage_options['client_kwargs']['endpoint_url']).netloc}/{path.path}"

webknossos/webknossos/utils.py

@@ -466,3 +466,12 @@ def check_version_in_thread() -> None:
     # Start the check in a daemon thread so it won't block program exit
     t = Thread(target=check_version_in_thread, daemon=True)
     t.start()
+
+
+def safe_is_relative_to(path: Path, base_path: Path) -> bool:
+    if (
+        (is_fs_path(path) and is_fs_path(base_path))
+        or UPath(path).protocol == UPath(base_path).protocol
+    ) and path.is_relative_to(base_path):
+        return True
+    return False