Fix add_symlink_layer properties lookup (#365)

Author: fm3

Changelog.md

@@ -18,6 +18,7 @@ For upgrade instructions, please check the respective *Breaking Changes* section
 ### Changed
 
 ### Fixed
+- Fixed a bug where Dataset.add_symlink_layer(make_relative=True) failed to look up dataset properties. [#365](https://github.com/scalableminds/webknossos-cuber/pull/365)
 
 ## [0.8.4](https://github.com/scalableminds/webknossos-cuber/releases/tag/v0.8.4) - 2021-07-26
 [Commits](https://github.com/scalableminds/webknossos-cuber/compare/v0.8.3...v0.8.4)

wkcuber/api/dataset.py

@@ -419,15 +419,18 @@ def add_symlink_layer(
         If make_relative is True, the symlink is made relative to the current dataset path.
         """
         foreign_layer_path = Path(os.path.abspath(foreign_layer_path))
-        if make_relative:
-            foreign_layer_path = Path(os.path.relpath(foreign_layer_path, self.path))
         layer_name = foreign_layer_path.name
         if layer_name in self.layers.keys():
             raise IndexError(
                 f"Cannot create symlink to {foreign_layer_path}. This dataset already has a layer called {layer_name}."
             )
 
-        os.symlink(foreign_layer_path, join(self.path, layer_name))
+        foreign_layer_symlink_path = (
+            Path(os.path.relpath(foreign_layer_path, self.path))
+            if make_relative
+            else foreign_layer_path
+        )
+        os.symlink(foreign_layer_symlink_path, join(self.path, layer_name))
 
         # copy the properties of the layer into the properties of this dataset
         layer_properties = Dataset(foreign_layer_path.parent).properties.data_layers[