Backwards compatibility shim

Author: maxrjones

src/zarr/core/chunk_grids.py

@@ -762,3 +762,28 @@ def _auto_partition(
             _shards_out = cast("tuple[int, ...]", shard_shape)
 
     return _shards_out, _chunks_out
+
+
+# -- Backwards-compatibility shim --
+# Downstream packages (tifffile, cubed, ismip-indexing) import RegularChunkGrid
+# from this module. Emit a deprecation warning and redirect to the metadata class.
+
+_DEPRECATED_NAMES = {
+    "RegularChunkGrid": "RegularChunkGridMetadata",
+    "RectilinearChunkGrid": "RectilinearChunkGridMetadata",
+}
+
+
+def __getattr__(name: str) -> Any:
+    if name in _DEPRECATED_NAMES:
+        new_name = _DEPRECATED_NAMES[name]
+        import zarr.core.metadata.v3 as v3_mod
+
+        warnings.warn(
+            f"Importing {name} from zarr.core.chunk_grids is deprecated. "
+            f"Use zarr.core.metadata.v3.{new_name} instead.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return getattr(v3_mod, new_name)
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")

tests/test_unified_chunk_grid.py

@@ -2735,3 +2735,37 @@ def test_property_block_indexing_rectilinear(data: st.DataObject) -> None:
             a[tuple(sel)],
             err_msg=f"dim={dim}, block={block_ix}",
         )
+
+
+# ---------------------------------------------------------------------------
+# Backwards-compatibility: import RegularChunkGrid from zarr.core.chunk_grids
+# ---------------------------------------------------------------------------
+# Downstream packages (tifffile, cubed, ismip-indexing) use this pattern:
+#   from zarr.core.chunk_grids import RegularChunkGrid
+#   RegularChunkGrid(chunk_shape=(...))
+
+
+def test_regular_chunk_grid_import_from_chunk_grids() -> None:
+    """RegularChunkGrid can be imported from zarr.core.chunk_grids with deprecation warning."""
+    with pytest.warns(DeprecationWarning, match="RegularChunkGrid"):
+        from zarr.core.chunk_grids import RegularChunkGrid
+
+    assert RegularChunkGrid is RegularChunkGridMetadata
+
+
+def test_regular_chunk_grid_construction_from_chunk_grids() -> None:
+    """RegularChunkGrid(chunk_shape=...) works when imported from zarr.core.chunk_grids."""
+    with pytest.warns(DeprecationWarning, match="RegularChunkGrid"):
+        from zarr.core.chunk_grids import RegularChunkGrid
+
+    grid = RegularChunkGrid(chunk_shape=(10, 20))
+    assert grid.chunk_shape == (10, 20)
+
+
+def test_regular_chunk_grid_isinstance_from_chunk_grids() -> None:
+    """isinstance check works for RegularChunkGrid imported from zarr.core.chunk_grids."""
+    with pytest.warns(DeprecationWarning, match="RegularChunkGrid"):
+        from zarr.core.chunk_grids import RegularChunkGrid
+
+    grid = RegularChunkGrid(chunk_shape=(10, 20))
+    assert isinstance(grid, RegularChunkGrid)