Move preserve_chunks call out of normalize_chunks

Author: jsignell

xarray/namedarray/daskmanager.py

@@ -55,18 +55,6 @@ def normalize_chunks(
         """Called by open_dataset"""
         from dask.array.core import normalize_chunks
 
-        if any(c == "preserve" for c in chunks) and any(c == "auto" for c in chunks):
-            raise ValueError('chunks cannot use a combination of "auto" and "preserve"')
-
-        if shape and previous_chunks and any(c == "preserve" for c in chunks):
-            chunks = self.preserve_chunks(
-                chunks,
-                shape=shape,
-                target=self.get_auto_chunk_size(),
-                typesize=getattr(dtype, "itemsize", 8),
-                previous_chunks=previous_chunks,
-            )
-
         return normalize_chunks(
             chunks,
             shape=shape,

xarray/namedarray/utils.py

@@ -236,6 +236,20 @@ def _get_chunk(  # type: ignore[no-untyped-def]
         limit = None
         dtype = data.dtype
 
+    if any(c == "preserve" for c in chunk_shape) and any(
+        c == "auto" for c in chunk_shape
+    ):
+        raise ValueError('chunks cannot use a combination of "auto" and "preserve"')
+
+    if shape and preferred_chunk_shape and any(c == "preserve" for c in chunk_shape):
+        chunk_shape = chunkmanager.preserve_chunks(
+            chunk_shape,
+            shape=shape,
+            target=chunkmanager.get_auto_chunk_size(),
+            typesize=getattr(dtype, "itemsize", 8),
+            previous_chunks=preferred_chunk_shape,
+        )
+
     chunk_shape = chunkmanager.normalize_chunks(
         chunk_shape,
         shape=shape,