From cf87ba4ba7a43727b94eaafa25bf9fcd368b43c2 Mon Sep 17 00:00:00 2001
From: Lukas Trippe <lkstrp@pm.me>
Date: Mon, 28 Oct 2024 22:57:12 +0100
Subject: [PATCH] Raise `ValueError` for unmatching chunks length in
 `DataArray.chunk()` (#9689)

* add `ValueError`

* add test
---
 xarray/core/dataarray.py       | 5 +++++
 xarray/tests/test_dataarray.py | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index db7824d8c90..c6bc082f5ed 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -1444,6 +1444,11 @@ def chunk(
                 "It will raise an error in the future. Instead use a dict with dimension names as keys.",
                 category=DeprecationWarning,
             )
+            if len(chunks) != len(self.dims):
+                raise ValueError(
+                    f"chunks must have the same number of elements as dimensions. "
+                    f"Expected {len(self.dims)} elements, got {len(chunks)}."
+                )
             chunk_mapping = dict(zip(self.dims, chunks, strict=True))
         else:
             chunk_mapping = either_dict_or_kwargs(chunks, chunks_kwargs, "chunk")
diff --git a/xarray/tests/test_dataarray.py b/xarray/tests/test_dataarray.py
index 78db39c194e..bff5ca8298d 100644
--- a/xarray/tests/test_dataarray.py
+++ b/xarray/tests/test_dataarray.py
@@ -897,6 +897,9 @@ def test_chunk(self) -> None:
             assert blocked.chunks == ((3,), (3, 1))
             assert blocked.data.name != first_dask_name
 
+            with pytest.raises(ValueError):
+                blocked.chunk(chunks=(3, 3, 3))
+
         # name doesn't change when rechunking by same amount
         # this fails if ReprObject doesn't have __dask_tokenize__ defined
         assert unblocked.chunk(2).data.name == unblocked.chunk(2).data.name