fix/group no error

src/zarr/api/asynchronous.py

@@ -673,13 +673,6 @@ async def group(
 
     zarr_format = _handle_zarr_version_or_format(zarr_version=zarr_version, zarr_format=zarr_format)
 
-    mode: AccessModeLiteral
-    if overwrite:
-        mode = "w"
-    else:
-        mode = "r+"
-    store_path = await make_store_path(store, path=path, mode=mode, storage_options=storage_options)
-
     if chunk_store is not None:
         warnings.warn("chunk_store is not yet implemented", ZarrRuntimeWarning, stacklevel=2)
     if cache_attrs is not None:
@@ -689,20 +682,7 @@ async def group(
     if meta_array is not None:
         warnings.warn("meta_array is not yet implemented", ZarrRuntimeWarning, stacklevel=2)
 
-    if attributes is None:
-        attributes = {}
-
-    try:
-        return await AsyncGroup.open(store=store_path, zarr_format=zarr_format)
-    except (KeyError, FileNotFoundError):
-        _zarr_format = zarr_format or _default_zarr_format()
-        return await AsyncGroup.from_store(
-            store=store_path,
-            zarr_format=_zarr_format,
-            overwrite=overwrite,
-            attributes=attributes,
-        )
-
+    return await create_group(store=store, path=path, overwrite=overwrite, zarr_format=zarr_format, attributes=attributes, storage_options=storage_options)
 
 async def create_group(
     *,
@@ -742,9 +722,7 @@ async def create_group(
     if zarr_format is None:
         zarr_format = _default_zarr_format()
 
-    mode: Literal["a"] = "a"
-
-    store_path = await make_store_path(store, path=path, mode=mode, storage_options=storage_options)
+    store_path = await make_store_path(store, path=path, mode="a", storage_options=storage_options)
 
     return await AsyncGroup.from_store(
         store=store_path,

tests/test_api/test_asynchronous.py

@@ -8,10 +8,12 @@
 import pytest
 
 from zarr import create_array
-from zarr.api.asynchronous import _get_shape_chunks, _like_args, open
+from zarr.api.asynchronous import _get_shape_chunks, _like_args, group, open
 from zarr.core.buffer.core import default_buffer_prototype
+from zarr.errors import ContainsGroupError
 
 if TYPE_CHECKING:
+    from pathlib import Path
     from typing import Any
 
     import numpy.typing as npt
@@ -103,3 +105,27 @@ async def test_open_no_array() -> None:
         TypeError, match=r"open_group\(\) got an unexpected keyword argument 'shape'"
     ):
         await open(store=store, shape=(1,))
+
+
+async def test_open_group_new_path(tmp_path: Path) -> None:
+    """
+    Test that zarr.api.asynchronous.group properly handles a string representation of a local file
+    path that does not yet exist.
+
+    See https://github.com/zarr-developers/zarr-python/issues/3406
+    """
+    # tmp_path exists, but tmp_path / "test.zarr" will not, which is important for this test
+    store = tmp_path / "test.zarr"
+    await group(store=store)
+
+
+async def test_open_group_old_path(tmp_path: Path) -> None:
+    """
+    Test that zarr.api.asynchronous.group will not overwrite an existing file.
+
+    See https://github.com/zarr-developers/zarr-python/issues/3406
+    """
+    store = tmp_path
+    await group(store=store, overwrite=True, attributes={"existing_group": True})
+    with pytest.raises(ContainsGroupError):
+        await group(store=store)

tests/test_group.py

@@ -2159,7 +2159,7 @@ def test_group_members_performance(store: Store) -> None:
 
     latency_store = LatencyStore(store, get_latency=get_latency)
     # create a group with some latency on get operations
-    group_read = zarr.group(store=latency_store)
+    group_read = zarr.open_group(store=latency_store)
 
     # check how long it takes to iterate over the groups
     # if .members is sensitive to IO latency,