From 2e1c06bc36ceb881f349ed3758e88b9d9cd405ba Mon Sep 17 00:00:00 2001
From: Mayeul d'Avezac <2745737+mdavezac@users.noreply.github.com>
Date: Wed, 10 Apr 2019 10:57:52 +0100
Subject: [PATCH 1/4] Indexing with an empty array

Closes #2882
---
 xarray/core/dataset.py         |  4 +++-
 xarray/tests/test_dataarray.py | 12 ++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index cf6631fa5ba..769e976a527 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -8,7 +8,7 @@
 from distutils.version import LooseVersion
 from numbers import Number
 from typing import (
-    Any, Callable, Dict, List, Optional, Set, Tuple, TypeVar, Union)
+    Any, Callable, Dict, List, Optional, Set, Tuple, TypeVar, Union, Sequence)
 
 import numpy as np
 import pandas as pd
@@ -1516,6 +1516,8 @@ def _validate_indexers(
                 v = as_variable(v)
             elif isinstance(v, Dataset):
                 raise TypeError('cannot use a Dataset as an indexer')
+            elif isinstance(v, Sequence) and len(v) == 0:
+                v = IndexVariable((k, ), np.asarray(v, dtype='int64'))
             else:
                 v = np.asarray(v)
 
diff --git a/xarray/tests/test_dataarray.py b/xarray/tests/test_dataarray.py
index b1ecf160533..99a1dfdddae 100644
--- a/xarray/tests/test_dataarray.py
+++ b/xarray/tests/test_dataarray.py
@@ -501,6 +501,18 @@ def test_getitem_dataarray(self):
         assert_equal(da[ind], da[[0, 1]])
         assert_equal(da[ind], da[ind.values])
 
+    def test_getitem_empty_index(self):
+        da = DataArray(np.arange(12).reshape((3, 4)), dims=['x', 'y'])
+        assert da[{'x': []}].size == 0
+        assert da[{'x': []}].x.size == 0
+        assert da[{'x': []}].y.size == da.y.size
+
+        assert da.loc[{'x': []}].size == 0
+        assert da.loc[{'x': []}].x.size == 0
+        assert da.loc[{'x': []}].y.size == da.y.size
+
+        assert da[[]].shape == da.values[[]].shape
+
     def test_setitem(self):
         # basic indexing should work as numpy's indexing
         tuples = [(0, 0), (0, slice(None, None)),

From abc4b38d4ea77dc1d6f6b24546d8b714579da9c5 Mon Sep 17 00:00:00 2001
From: Mayeul d'Avezac <2745737+mdavezac@users.noreply.github.com>
Date: Wed, 10 Apr 2019 11:15:30 +0100
Subject: [PATCH 2/4] Adds 2882 resolution to whats-new.rst

---
 doc/whats-new.rst | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 4c126196469..f67cf2a7c02 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -24,6 +24,9 @@ Enhancements
 Bug fixes
 ~~~~~~~~~
 
+- indexing with an empty list creates an object with zero-length axis (:issue:`2882`)
+  By `Mayeul d'Avezac <https://github.com/mdavezac>`_.
+
 .. _whats-new.0.12.1:
 
 v0.12.1 (4 April 2019)

From 5412729988431d92ef5b0847e64198ccfe3dc412 Mon Sep 17 00:00:00 2001
From: Mayeul d'Avezac <2745737+mdavezac@users.noreply.github.com>
Date: Thu, 11 Apr 2019 09:12:53 +0100
Subject: [PATCH 3/4] Create empty indexing array directly

---
 xarray/core/dataset.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 769e976a527..1a866bf7781 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -1517,7 +1517,7 @@ def _validate_indexers(
             elif isinstance(v, Dataset):
                 raise TypeError('cannot use a Dataset as an indexer')
             elif isinstance(v, Sequence) and len(v) == 0:
-                v = IndexVariable((k, ), np.asarray(v, dtype='int64'))
+                v = IndexVariable((k, ), np.zeros((0,), dtype='int64'))
             else:
                 v = np.asarray(v)
 

From cf0052f9863a597cddc6b34ff8d8b983774c8618 Mon Sep 17 00:00:00 2001
From: Mayeul d'Avezac <2745737+mdavezac@users.noreply.github.com>
Date: Thu, 11 Apr 2019 09:17:12 +0100
Subject: [PATCH 4/4] assert xxx -> asset_identical

---
 xarray/tests/test_dataarray.py | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/xarray/tests/test_dataarray.py b/xarray/tests/test_dataarray.py
index 99a1dfdddae..58eb6a1d6dc 100644
--- a/xarray/tests/test_dataarray.py
+++ b/xarray/tests/test_dataarray.py
@@ -503,15 +503,11 @@ def test_getitem_dataarray(self):
 
     def test_getitem_empty_index(self):
         da = DataArray(np.arange(12).reshape((3, 4)), dims=['x', 'y'])
-        assert da[{'x': []}].size == 0
-        assert da[{'x': []}].x.size == 0
-        assert da[{'x': []}].y.size == da.y.size
-
-        assert da.loc[{'x': []}].size == 0
-        assert da.loc[{'x': []}].x.size == 0
-        assert da.loc[{'x': []}].y.size == da.y.size
-
-        assert da[[]].shape == da.values[[]].shape
+        assert_identical(da[{'x': []}],
+                         DataArray(np.zeros((0, 4)), dims=['x', 'y']))
+        assert_identical(da.loc[{'y': []}],
+                         DataArray(np.zeros((3, 0)), dims=['x', 'y']))
+        assert_identical(da[[]], DataArray(np.zeros((0, 4)), dims=['x', 'y']))
 
     def test_setitem(self):
         # basic indexing should work as numpy's indexing