Only inspect alternate node type if desired isn't present (#696)

Co-authored-by: Josh Moore <j.a.moore@dundee.ac.uk>

Author: manzt

zarr/creation.py

@@ -507,9 +507,9 @@ def open_array(
     # ensure store is initialized
 
     if mode in ['r', 'r+']:
-        if contains_group(store, path=path):
-            raise ContainsGroupError(path)
-        elif not contains_array(store, path=path):
+        if not contains_array(store, path=path):
+            if contains_group(store, path=path):
+                raise ContainsGroupError(path)
             raise ArrayNotFoundError(path)
 
     elif mode == 'w':
@@ -519,9 +519,9 @@ def open_array(
                    object_codec=object_codec, chunk_store=chunk_store)
 
     elif mode == 'a':
-        if contains_group(store, path=path):
-            raise ContainsGroupError(path)
-        elif not contains_array(store, path=path):
+        if not contains_array(store, path=path):
+            if contains_group(store, path=path):
+                raise ContainsGroupError(path)
             init_array(store, shape=shape, chunks=chunks, dtype=dtype,
                        compressor=compressor, fill_value=fill_value,
                        order=order, filters=filters, path=path,

zarr/hierarchy.py

@@ -1162,18 +1162,18 @@ def open_group(store=None, mode='a', cache_attrs=True, synchronizer=None, path=N
     # ensure store is initialized
 
     if mode in ['r', 'r+']:
-        if contains_array(store, path=path):
-            raise ContainsArrayError(path)
-        elif not contains_group(store, path=path):
+        if not contains_group(store, path=path):
+            if contains_array(store, path=path):
+                raise ContainsArrayError(path)
             raise GroupNotFoundError(path)
 
     elif mode == 'w':
         init_group(store, overwrite=True, path=path, chunk_store=chunk_store)
 
     elif mode == 'a':
-        if contains_array(store, path=path):
-            raise ContainsArrayError(path)
         if not contains_group(store, path=path):
+            if contains_array(store, path=path):
+                raise ContainsArrayError(path)
             init_group(store, path=path, chunk_store=chunk_store)
 
     elif mode in ['w-', 'x']: