Switch to ButlerURI for relative path calculation.

lsst · Nov 17, 2020 · eebffa6 · eebffa6
1 parent 5da0cb0
commit eebffa6
Showing 1 changed file with 5 additions and 4 deletions.
diff --git a/python/lsst/obs/base/gen2to3/convertRepo.py b/python/lsst/obs/base/gen2to3/convertRepo.py
@@ -30,6 +30,7 @@
 
 from lsst.daf.butler import (
     Butler as Butler3,
+    ButlerURI,
     CollectionType,
     SkyPixDimension
 )
@@ -138,10 +139,10 @@ def guessCollectionNames(self, instrument: Instrument, root: str) -> None:
             return
         if self.chainName is None:
             if os.path.isabs(self.path):
-                if not os.path.isabs(root):
-                    root = os.path.abspath(root)
-                chainName = os.path.relpath(self.path, root)
-                if chainName.startswith(".."):
+                rerunURI = ButlerURI(self.path)
+                rootURI = ButlerURI(root)
+                chainName = rerunURI.relative_to(rootURI)
+                if chainName is None:
                     raise ValueError(
                         f"Cannot guess run name collection for rerun at '{self.path}': "
                         f"no clear relationship to root '{root}'."