fix: apply path normalization to fsspec store

changes/3924.bugfix.md

@@ -0,0 +1 @@
+Apply path normalization to the `path` attribute of `FsspecStore`.

src/zarr/storage/_fsspec.py

@@ -16,7 +16,7 @@
 )
 from zarr.core.buffer import Buffer
 from zarr.errors import ZarrUserWarning
-from zarr.storage._utils import _join_paths
+from zarr.storage._utils import _join_paths, normalize_path
 
 if TYPE_CHECKING:
     from collections.abc import AsyncIterator, Iterable
@@ -127,7 +127,7 @@ def __init__(
     ) -> None:
         super().__init__(read_only=read_only)
         self.fs = fs
-        self.path = path
+        self.path = normalize_path(path)
         self.allowed_exceptions = allowed_exceptions
 
         if not self.fs.async_impl:

tests/test_store/test_fsspec.py

@@ -17,6 +17,7 @@
 from zarr.errors import ZarrUserWarning
 from zarr.storage import FsspecStore
 from zarr.storage._fsspec import _make_async
+from zarr.storage._utils import normalize_path
 from zarr.testing.store import StoreTests
 
 if TYPE_CHECKING:
@@ -286,6 +287,27 @@ def array_roundtrip(store: FsspecStore) -> None:
     np.testing.assert_array_equal(arr[:], data)
 
 
+@pytest.mark.skipif(
+    parse_version(fsspec.__version__) < parse_version("2024.12.0"),
+    reason="No AsyncFileSystemWrapper",
+)
+@pytest.mark.parametrize("path", ["", "/", "//", "foo", "foo/", "/foo", "/foo/", "//foo//"])
+def test_fsspec_store_path_normalization(path: str) -> None:
+    """`FsspecStore.path` is normalized to the canonical form, matching
+    `normalize_path`, regardless of the surface representation the caller
+    supplies.
+
+    Regression test for https://github.com/zarr-developers/zarr-python/issues/3922
+    -- when a caller passed `path="/"` the leading slash flowed through
+    unmodified to subsequent `_join_paths([self.path, key])` calls, producing
+    `"//key"` and missing the underlying object.
+    """
+    sync_fs = fsspec.filesystem("memory")
+    fs = _make_async(sync_fs)
+    store = FsspecStore(fs=fs, path=path)
+    assert store.path == normalize_path(path)
+
+
 @pytest.mark.skipif(
     parse_version(fsspec.__version__) < parse_version("2024.12.0"),
     reason="No AsyncFileSystemWrapper",