simplify

Author: TomAugspurger

src/zarr/store/memory.py

@@ -114,17 +114,15 @@ async def list_dir(self, prefix: str) -> AsyncGenerator[str, None]:
 
         if prefix == "":
             keys_unique = set(k.split("/")[0] for k in self._store_dict.keys())
-            for key in keys_unique:
-                yield key
         else:
             # Our dictionary doesn't contain directory markers, but we want to include
             # a pseudo directory when there's a nested item and we're listing an
             # intermediate level.
-            n = prefix.count("/") + 2
             keys_unique = {
-                "/".join(k.split("/", n)[:n])
-                for k in self._store_dict
-                if k.startswith(prefix + "/")
+                key.removeprefix(prefix + "/").split("/")[0]
+                for key in self._store_dict
+                if key.startswith(prefix + "/") and key != prefix
             }
-            for key in keys_unique:
-                yield key.removeprefix(prefix + "/").split("/")[0]
+
+        for key in keys_unique:
+            yield key