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fix: validate that dask-style chunks have regular shapes #3779

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fix: validate that dask-style chunks have regular shapes #3779

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90da488
fix: validate that dask-style chunks have regular shapes
maxrjones Mar 13, 2026
293977e
Apply suggestion from @dcherian
maxrjones Mar 13, 2026
9ad42a6
Fix shortcircuit option
maxrjones Mar 13, 2026
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13 changes: 8 additions & 5 deletions src/zarr/core/chunk_grids.py
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Original file line number Diff line number Diff line change
Expand Up @@ -126,11 +126,14 @@ def normalize_chunks(chunks: Any, shape: tuple[int, ...], typesize: int) -> tupl
chunks = tuple(int(chunks) for _ in shape)

# handle dask-style chunks (iterable of iterables)
if all(isinstance(c, (tuple | list)) for c in chunks):
# take first chunk size for each dimension
chunks = tuple(
c[0] for c in chunks
) # TODO: check/error/warn for irregular chunks (e.g. if c[0] != c[1:-1])
if all(isinstance(c, (tuple, list)) for c in chunks):
for i, c in enumerate(chunks):
if any(x != y for x, y in itertools.pairwise(c[:-1])) or (len(c) > 1 and c[-1] > c[0]):
raise ValueError(
f"Irregular chunk sizes in dimension {i}: {tuple(c)}. "
"Only uniform chunks (with an optional smaller final chunk) are supported."
)
chunks = tuple(c[0] for c in chunks)

# handle bad dimensionality
if len(chunks) > len(shape):
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9 changes: 9 additions & 0 deletions tests/test_chunk_grids.py
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,10 @@ def test_guess_chunks(shape: tuple[int, ...], itemsize: int) -> None:
((30, None, None), (100, 20, 10), 1, (30, 20, 10)),
((30, 20, None), (100, 20, 10), 1, (30, 20, 10)),
((30, 20, 10), (100, 20, 10), 1, (30, 20, 10)),
# dask-style chunks (uniform with optional smaller final chunk)
(((100, 100, 100), (50, 50)), (300, 100), 1, (100, 50)),
(((100, 100, 50),), (250,), 1, (100,)),
(((100,),), (100,), 1, (100,)),
# auto chunking
(None, (100,), 1, (100,)),
(-1, (100,), 1, (100,)),
Expand All @@ -52,3 +56,8 @@ def test_normalize_chunks_errors() -> None:
normalize_chunks("foo", (100,), 1)
with pytest.raises(ValueError):
normalize_chunks((100, 10), (100,), 1)
# dask-style irregular chunks should raise
with pytest.raises(ValueError, match="Irregular chunk sizes"):
normalize_chunks(((10, 20, 30),), (60,), 1)
with pytest.raises(ValueError, match="Irregular chunk sizes"):
normalize_chunks(((100, 100), (10, 20)), (200, 30), 1)
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