From e3fe2491dead8a4537d1ec3a0360a84229113a46 Mon Sep 17 00:00:00 2001
From: Joseph K Aicher <4666753+jaicher@users.noreply.github.com>
Date: Thu, 26 Aug 2021 15:43:33 -0400
Subject: [PATCH 1/3] Added test_save_emptydim for zarr backends, which fails
 when chunking

Added test that fails when saving to zarr a dataset with a chunked array
that has a dimension of length zero (Issue #5741)
---
 xarray/tests/test_backends.py | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/xarray/tests/test_backends.py b/xarray/tests/test_backends.py
index 3ca20cade56..adb8e19f6d0 100644
--- a/xarray/tests/test_backends.py
+++ b/xarray/tests/test_backends.py
@@ -2186,6 +2186,16 @@ def test_to_zarr_append_compute_false_roundtrip(self):
                 with self.open(store) as actual:
                     assert_identical(xr.concat([ds, ds_to_append], dim="time"), actual)
 
+    @pytest.mark.parametrize("chunk", [False, True])
+    def test_save_emptydim(self, chunk):
+        if chunk and not has_dask:
+            pytest.skip("requires dask")
+        ds = Dataset({"x": (("a", "b"), np.empty((5, 0))), "y": ("a", [1, 2, 5, 8, 9])})
+        if chunk:
+            ds = ds.chunk({})  # chunk dataset to save dask array
+        with self.roundtrip(ds) as ds_reload:
+            assert_identical(ds, ds_reload)
+
     @pytest.mark.parametrize("consolidated", [False, True])
     @pytest.mark.parametrize("compute", [False, True])
     @pytest.mark.parametrize("use_dask", [False, True])

From cc01b35f1137db55a7cb5d415aa4c3df55d8d866 Mon Sep 17 00:00:00 2001
From: Joseph K Aicher <4666753+jaicher@users.noreply.github.com>
Date: Thu, 26 Aug 2021 15:57:29 -0400
Subject: [PATCH 2/3] Load all variables with zero entries before saving
 to_zarr

This addresses Issue #5741 and allows `test_save_emptydim` to pass. We
get around `to_zarr` not liking dask arrays with zero length dimensions
by giving it numpy arrays, which works for some reason
---
 xarray/backends/api.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/xarray/backends/api.py b/xarray/backends/api.py
index 2c9b25f860f..7b9980e035f 100644
--- a/xarray/backends/api.py
+++ b/xarray/backends/api.py
@@ -1327,6 +1327,11 @@ def to_zarr(
     See `Dataset.to_zarr` for full API docs.
     """
 
+    # Load empty arrays to avoid bug saving zero length dimensions (Issue #5741)
+    for v in dataset.variables.values():
+        if v.size == 0:
+            v.load()
+
     # expand str and Path arguments
     store = _normalize_path(store)
     chunk_store = _normalize_path(chunk_store)

From 09e39870afd19107e4beaac40b48f2ec55e9cc7f Mon Sep 17 00:00:00 2001
From: Joseph K Aicher <4666753+jaicher@users.noreply.github.com>
Date: Thu, 26 Aug 2021 16:06:14 -0400
Subject: [PATCH 3/3] Updated whats-new.rst with information about fix for
 #5741

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

diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 348188cbd26..b4c26b278f1 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -57,6 +57,9 @@ Deprecations
 Bug fixes
 ~~~~~~~~~
 
+- Fix ZeroDivisionError from saving dask array with empty dimension (:issue: `5741`).
+  By `Joseph K Aicher <https://github.com/jaicher>`_.
+
 
 Documentation
 ~~~~~~~~~~~~~