Allow rechunk to take a dict for chunks (#226)

cubed/core/ops.py

@@ -590,16 +590,19 @@ def wrap(*a, block_id=None, **kw):
 
 
 def rechunk(x, chunks, target_store=None):
-    if x.chunks == normalize_chunks(chunks, x.shape, dtype=x.dtype):
+    normalized_chunks = normalize_chunks(chunks, x.shape, dtype=x.dtype)
+    if x.chunks == normalized_chunks:
         return x
+    # normalizing takes care of dict args for chunks
+    target_chunks = to_chunksize(normalized_chunks)
     name = gensym()
     spec = x.spec
     if target_store is None:
         target_store = new_temp_path(name=name, spec=spec)
     temp_store = new_temp_path(name=f"{name}-intermediate", spec=spec)
     pipeline = primitive_rechunk(
         x.zarray_maybe_lazy,
-        target_chunks=chunks,
+        target_chunks=target_chunks,
         allowed_mem=spec.allowed_mem,
         reserved_mem=spec.reserved_mem,
         target_store=target_store,

cubed/primitive/rechunk.py

@@ -7,11 +7,7 @@
 from cubed.runtime.pipeline import spec_to_pipeline
 from cubed.storage.zarr import lazy_empty
 from cubed.vendor.rechunker.algorithm import rechunking_plan
-from cubed.vendor.rechunker.api import (
-    _get_dims_from_zarr_array,
-    _shape_dict_to_tuple,
-    _validate_options,
-)
+from cubed.vendor.rechunker.api import _validate_options
 
 
 def rechunk(
@@ -119,16 +115,6 @@ def _setup_array_rechunk(
         # this is just a pass-through copy
         target_chunks = source_chunks
 
-    if isinstance(target_chunks, dict):
-        array_dims = _get_dims_from_zarr_array(source_array)
-        try:
-            target_chunks = _shape_dict_to_tuple(array_dims, target_chunks)
-        except KeyError:
-            raise KeyError(
-                "You must explicitly specify each dimension size in target_chunks. "
-                f"Got array_dims {array_dims}, target_chunks {target_chunks}."
-            )
-
     # TODO: rewrite to avoid the hard dependency on dask
     max_mem = cubed.vendor.dask.utils.parse_bytes(max_mem)
 

cubed/tests/test_core.py

@@ -197,9 +197,10 @@ def test_multiple_ops(spec, executor):
     )
 
 
-def test_rechunk(spec, executor):
+@pytest.mark.parametrize("new_chunks", [(1, 2), {0: 1, 1: 2}])
+def test_rechunk(spec, executor, new_chunks):
     a = xp.asarray([[1, 2, 3], [4, 5, 6], [7, 8, 9]], chunks=(2, 1), spec=spec)
-    b = a.rechunk((1, 2))
+    b = a.rechunk(new_chunks)
     assert_array_equal(
         b.compute(executor=executor),
         np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]),