added deprecation warning

Author: Lily Wang

xarray/backends/zarr.py

@@ -1,5 +1,7 @@
 from __future__ import absolute_import, division, print_function
 
+import warnings
+
 from distutils.version import LooseVersion
 
 import numpy as np
@@ -327,11 +329,11 @@ def sync(self):
         pass
 
 
-def open_zarr(store, group=None, synchronizer=None, chunks=None,
+def open_zarr(store, group=None, synchronizer=None, chunks='auto',
               decode_cf=True, mask_and_scale=True, decode_times=True,
               concat_characters=True, decode_coords=True,
-              drop_variables=None, auto_chunk=True,
-              overwrite_encoded_chunks=False):
+              drop_variables=None, overwrite_encoded_chunks=False, 
+              **kwargs):
     """Load and decode a dataset from a Zarr store.
 
     .. note:: Experimental
@@ -354,13 +356,8 @@ def open_zarr(store, group=None, synchronizer=None, chunks=None,
     chunks : int or dict or {None, 'auto'}, optional
         Chunk sizes along each dimension, e.g., ``5`` or
         ``{'x': 5, 'y': 5}``. If `chunks='auto'`, dask chunks are created
-        based on the variable's zarr chunks. If `chunks=None` and
-        `auto_chunk=False`, zarr array data will lazily convert to numpy
-        arrays upon access.
-    auto_chunk : bool, optional
-        Whether to automatically create dask chunks corresponding to each
-        variable's zarr chunks. If `chunks=None`, this overrides `chunks`.
-        Equivalent to `chunks='auto'.` (Default: True)
+        based on the variable's zarr chunks. If `chunks=None`, zarr array
+        data will lazily convert to numpy arrays upon access.
     overwrite_encoded_chunks: bool, optional
         Whether to drop the zarr chunks encoded for each variable when a
         dataset is loaded with specified chunk sizes (default: False)
@@ -404,9 +401,19 @@ def open_zarr(store, group=None, synchronizer=None, chunks=None,
     ----------
     http://zarr.readthedocs.io/
     """
-
-    if auto_chunk and chunks is None:
-        chunks = 'auto'  # maintain backwards compatibility
+    if 'auto_chunk' in kwargs:
+        auto_chunk = kwargs.pop('auto_chunk')
+        if auto_chunk == True:
+            chunks = 'auto'  # maintain backwards compatibility
+        elif auto_chunk == False:
+            chunks = None
+
+        warnings.warn("auto_chunk is deprecated. Use chunks='auto' instead.",
+                      FutureWarning, stacklevel=2)
+
+    if kwargs:
+        raise TypeError("open_zarr() got unexpected keyword arguments " +
+                        ",".join(kwargs.keys()))
 
     if not isinstance(chunks, (int, dict)):
         if chunks != 'auto' and chunks is not None:

xarray/tests/test_backends.py

@@ -1325,15 +1325,15 @@ def test_auto_chunk(self):
         original = create_test_data().chunk()
 
         with self.roundtrip(
-                original, open_kwargs={'auto_chunk': False}) as actual:
+                original, open_kwargs={'chunks': None}) as actual:
             for k, v in actual.variables.items():
                 # only index variables should be in memory
                 assert v._in_memory == (k in actual.dims)
                 # there should be no chunks
                 assert v.chunks is None
 
         with self.roundtrip(
-                original, open_kwargs={'auto_chunk': True}) as actual:
+                original, open_kwargs={'chunks': 'auto'}) as actual:
             for k, v in actual.variables.items():
                 # only index variables should be in memory
                 assert v._in_memory == (k in actual.dims)
@@ -1346,7 +1346,7 @@ def test_manual_chunk(self):
         # All of these should return non-chunked arrays
         NO_CHUNKS = (None, 0, {})
         for no_chunk in NO_CHUNKS:
-            open_kwargs = {'chunks': no_chunk, 'auto_chunk': False}
+            open_kwargs = {'chunks': no_chunk}
             with self.roundtrip(original, open_kwargs=open_kwargs) as actual:
                 for k, v in actual.variables.items():
                     # only index variables should be in memory
@@ -1380,13 +1380,33 @@ def test_manual_chunk(self):
 
                 assert_identical(actual, auto)
                 assert_identical(actual.load(), auto.load())
+    
+    def test_deprecate_auto_chunk(self):
+        original = create_test_data().chunk()
+        with pytest.warns(FutureWarning):
+            with self.roundtrip(
+                original, open_kwargs={'auto_chunk': True}) as actual:
+                for k, v in actual.variables.items():
+                    # only index variables should be in memory
+                    assert v._in_memory == (k in actual.dims)
+                    # chunk size should be the same as original
+                    assert v.chunks == original[k].chunks
+        
+        with pytest.warns(FutureWarning):
+            with self.roundtrip(
+                original, open_kwargs={'auto_chunk': False}) as actual:
+                for k, v in actual.variables.items():
+                    # only index variables should be in memory
+                    assert v._in_memory == (k in actual.dims)
+                    # there should be no chunks
+                    assert v.chunks is None
+            
 
     def test_write_uneven_dask_chunks(self):
         # regression for GH#2225
         original = create_test_data().chunk({'dim1': 3, 'dim2': 4, 'dim3': 3})
-
         with self.roundtrip(
-                original, open_kwargs={'auto_chunk': True}) as actual:
+                original, open_kwargs={'chunks': 'auto'}) as actual:
             for k, v in actual.data_vars.items():
                 print(k)
                 assert v.chunks == actual[k].chunks