Fix distributed.Client.compute applied to DataArray (#3173)

* Fix distributed.Client.compute applied to DataArray

* type annotations

Author: crusaderky

doc/whats-new.rst

@@ -55,8 +55,11 @@ Bug fixes
   due to a ``datetime`` issue in NumPy (:issue:`2334`).
   By `Graham Inggs <https://github.com/ginggs>`_.
 - Fixed bug in ``combine_by_coords()`` causing a `ValueError` if the input had
-  an unused dimension with coordinates which were not monotonic (:issue`3150`).
+  an unused dimension with coordinates which were not monotonic (:issue:`3150`).
   By `Tom Nicholas <http://github.com/TomNicholas>`_.
+- Fixed crash when applying ``distributed.Client.compute()`` to a DataArray
+  (:issue:`3171`). By `Guido Imperiale <https://github.com/crusaderky>`_.
+
 
 .. _whats-new.0.12.3:
 

xarray/core/dataarray.py

@@ -300,7 +300,7 @@ def _replace(
         self,
         variable: Variable = None,
         coords=None,
-        name: Union[Hashable, None, ReprObject] = __default,
+        name: Optional[Hashable] = __default,
     ) -> 'DataArray':
         if variable is None:
             variable = self.variable
@@ -313,7 +313,7 @@ def _replace(
     def _replace_maybe_drop_dims(
             self,
             variable: Variable,
-            name: Union[str, None, utils.ReprObject] = __default
+            name: Optional[Hashable] = __default
     ) -> 'DataArray':
         if variable.dims == self.dims and variable.shape == self.shape:
             coords = self._coords.copy()
@@ -356,7 +356,7 @@ def _to_temp_dataset(self) -> Dataset:
     def _from_temp_dataset(
         self,
         dataset: Dataset,
-        name: Union[Hashable, ReprObject] = __default
+        name: Hashable = __default
     ) -> 'DataArray':
         variable = dataset._variables.pop(_THIS_ARRAY)
         coords = dataset._variables

xarray/core/utils.py

@@ -462,12 +462,22 @@ def __repr__(self: Any) -> str:
 class ReprObject:
     """Object that prints as the given value, for use with sentinel values.
     """
+    __slots__ = ('_value', )
+
     def __init__(self, value: str):
         self._value = value
 
     def __repr__(self) -> str:
         return self._value
 
+    def __eq__(self, other) -> bool:
+        if isinstance(other, ReprObject):
+            return self._value == other._value
+        return False
+
+    def __hash__(self) -> int:
+        return hash((ReprObject, self._value))
+
 
 @contextlib.contextmanager
 def close_on_error(f):

xarray/tests/test_utils.py

@@ -1,5 +1,6 @@
 from collections import OrderedDict
 from datetime import datetime
+from typing import Hashable
 
 import numpy as np
 import pandas as pd
@@ -179,6 +180,21 @@ def test_sorted_keys_dict(self):
 def test_repr_object():
     obj = utils.ReprObject('foo')
     assert repr(obj) == 'foo'
+    assert isinstance(obj, Hashable)
+    assert not isinstance(obj, str)
+
+
+def test_repr_object_magic_methods():
+    o1 = utils.ReprObject('foo')
+    o2 = utils.ReprObject('foo')
+    o3 = utils.ReprObject('bar')
+    o4 = 'foo'
+    assert o1 == o2
+    assert o1 != o3
+    assert o1 != o4
+    assert hash(o1) == hash(o2)
+    assert hash(o1) != hash(o3)
+    assert hash(o1) != hash(o4)
 
 
 def test_is_remote_uri():