Fix bug where newaxis with full slices doesn't add new axes (#559)

Author: tomwhite

cubed/core/ops.py

@@ -466,43 +466,45 @@ def merged_chunk_len_for_indexer(ia, c):
         return (c // ia.step) * ia.step
 
     shape = idx.newshape(x.shape)
+
     if shape == x.shape:
-        # no op case
-        return x
-    dtype = x.dtype
-    chunks = tuple(
-        chunk_len_for_indexer(ia, c)
-        for ia, c in zip(idx.args, x.chunksize)
-        if not isinstance(ia, ndindex.Integer)
-    )
+        # no op case (except possibly newaxis applied below)
+        out = x
+    else:
+        dtype = x.dtype
+        chunks = tuple(
+            chunk_len_for_indexer(ia, c)
+            for ia, c in zip(idx.args, x.chunksize)
+            if not isinstance(ia, ndindex.Integer)
+        )
 
-    target_chunks = normalize_chunks(chunks, shape, dtype=dtype)
+        target_chunks = normalize_chunks(chunks, shape, dtype=dtype)
 
-    # memory allocated by reading one chunk from input array
-    # note that although the output chunk will overlap multiple input chunks, zarr will
-    # read the chunks in series, reusing the buffer
-    extra_projected_mem = x.chunkmem
+        # memory allocated by reading one chunk from input array
+        # note that although the output chunk will overlap multiple input chunks, zarr will
+        # read the chunks in series, reusing the buffer
+        extra_projected_mem = x.chunkmem
 
-    out = map_direct(
-        _read_index_chunk,
-        x,
-        shape=shape,
-        dtype=dtype,
-        chunks=target_chunks,
-        extra_projected_mem=extra_projected_mem,
-        target_chunks=target_chunks,
-        selection=selection,
-    )
+        out = map_direct(
+            _read_index_chunk,
+            x,
+            shape=shape,
+            dtype=dtype,
+            chunks=target_chunks,
+            extra_projected_mem=extra_projected_mem,
+            target_chunks=target_chunks,
+            selection=selection,
+        )
 
-    # merge chunks for any dims with step > 1 so they are
-    # the same size as the input (or slightly smaller due to rounding)
-    merged_chunks = tuple(
-        merged_chunk_len_for_indexer(ia, c)
-        for ia, c in zip(idx.args, x.chunksize)
-        if not isinstance(ia, ndindex.Integer)
-    )
-    if chunks != merged_chunks:
-        out = merge_chunks(out, merged_chunks)
+        # merge chunks for any dims with step > 1 so they are
+        # the same size as the input (or slightly smaller due to rounding)
+        merged_chunks = tuple(
+            merged_chunk_len_for_indexer(ia, c)
+            for ia, c in zip(idx.args, x.chunksize)
+            if not isinstance(ia, ndindex.Integer)
+        )
+        if chunks != merged_chunks:
+            out = merge_chunks(out, merged_chunks)
 
     for axis in where_newaxis:
         from cubed.array_api.manipulation_functions import expand_dims

cubed/tests/test_indexing.py

@@ -20,6 +20,8 @@ def spec(tmp_path):
         [6, 7, 2, 9, 10],
         ([6, 7, 2, 9, 10], xp.newaxis),
         (xp.newaxis, [6, 7, 2, 9, 10]),
+        (slice(None), xp.newaxis),
+        (xp.newaxis, slice(None)),
     ],
 )
 def test_int_array_index_1d(spec, ind):
@@ -36,6 +38,9 @@ def test_int_array_index_1d(spec, ind):
         (xp.newaxis, slice(None), [2, 1]),
         (slice(None), xp.newaxis, [2, 1]),
         (slice(None), [2, 1], xp.newaxis),
+        (xp.newaxis, slice(None), slice(None)),
+        (slice(None), xp.newaxis, slice(None)),
+        (slice(None), slice(None), xp.newaxis),
     ],
 )
 def test_int_array_index_2d(spec, ind):