From a2d293765693bc826cbe6ed7a2d531d6b2f9401e Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Tue, 3 Mar 2020 21:19:38 -0500
Subject: [PATCH 01/10] allow ellipsis to be used in stack

---
 doc/reshaping.rst              | 7 +++++++
 xarray/core/dataset.py         | 2 ++
 xarray/tests/test_dataarray.py | 3 +++
 xarray/tests/test_dataset.py   | 6 ++++++
 4 files changed, 18 insertions(+)

diff --git a/doc/reshaping.rst b/doc/reshaping.rst
index 455a24f9216..251c01b6339 100644
--- a/doc/reshaping.rst
+++ b/doc/reshaping.rst
@@ -109,6 +109,12 @@ implemented :py:meth:`~xarray.DataArray.stack` and
     stacked
     stacked.unstack('z')
 
+As elsewhere in xarray, an ellipsis (`...`) can be used to represent all dimensions:
+
+.. ipython:: python
+    stacked = array.stack(z=...)
+    stacked
+
 These methods are modeled on the :py:class:`pandas.DataFrame` methods of the
 same name, although in xarray they always create new dimensions rather than
 adding to the existing index or columns.
@@ -164,6 +170,7 @@ like this:
                       'b': ('x', [6, 7])},
             coords={'y': ['u', 'v', 'w']}
         )
+        data
         stacked = data.to_stacked_array("z", sample_dims=['x'])
         stacked
         unstacked = stacked.to_unstacked_dataset("z")
diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 7252dd2f3df..3f5cf93a03b 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -3235,6 +3235,8 @@ def reorder_levels(
         return self._replace(variables, indexes=indexes)
 
     def _stack_once(self, dims, new_dim):
+        if dims == ... or dims == [...]:
+            dims = self.dims
         variables = {}
         for name, var in self.variables.items():
             if name not in dims:
diff --git a/xarray/tests/test_dataarray.py b/xarray/tests/test_dataarray.py
index 0a622d279ba..8f2332f9229 100644
--- a/xarray/tests/test_dataarray.py
+++ b/xarray/tests/test_dataarray.py
@@ -2040,6 +2040,9 @@ def test_stack_unstack(self):
         actual = orig.stack(z=["x", "y"]).unstack("z").drop_vars(["x", "y"])
         assert_identical(orig, actual)
 
+        actual = orig.stack(z=...).unstack("z").drop_vars(["x", "y"])
+        assert_identical(orig, actual)
+
         dims = ["a", "b", "c", "d", "e"]
         orig = xr.DataArray(np.random.rand(1, 2, 3, 2, 1), dims=dims)
         stacked = orig.stack(ab=["a", "b"], cd=["c", "d"])
diff --git a/xarray/tests/test_dataset.py b/xarray/tests/test_dataset.py
index 7bcf9379ae8..86bd1eb5f31 100644
--- a/xarray/tests/test_dataset.py
+++ b/xarray/tests/test_dataset.py
@@ -2868,6 +2868,12 @@ def test_stack(self):
         actual = ds.stack(z=["x", "y"])
         assert_identical(expected, actual)
 
+        actual = ds.stack(z=[...])
+        assert_identical(expected, actual)
+
+        actual = ds.stack(z=...)
+        assert_identical(expected, actual)
+
         exp_index = pd.MultiIndex.from_product([["a", "b"], [0, 1]], names=["y", "x"])
         expected = Dataset(
             {"a": ("z", [0, 1, 0, 1]), "b": ("z", [0, 2, 1, 3]), "z": exp_index}

From 875c3b999c1ad639c320eb8acb2388e4b1501b51 Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Tue, 3 Mar 2020 22:01:44 -0500
Subject: [PATCH 02/10] doc fix

---
 doc/reshaping.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/reshaping.rst b/doc/reshaping.rst
index 251c01b6339..881f841ea72 100644
--- a/doc/reshaping.rst
+++ b/doc/reshaping.rst
@@ -112,6 +112,7 @@ implemented :py:meth:`~xarray.DataArray.stack` and
 As elsewhere in xarray, an ellipsis (`...`) can be used to represent all dimensions:
 
 .. ipython:: python
+
     stacked = array.stack(z=...)
     stacked
 

From 48809a0684685f3d0bb81cc632ef91fcb5b57dfa Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Wed, 4 Mar 2020 07:19:03 -0500
Subject: [PATCH 03/10] support ellipsis only as part of an iterable

---
 xarray/core/dataset.py         | 2 +-
 xarray/tests/test_dataarray.py | 2 +-
 xarray/tests/test_dataset.py   | 3 ++-
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 3f5cf93a03b..51debd1e61d 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -3235,7 +3235,7 @@ def reorder_levels(
         return self._replace(variables, indexes=indexes)
 
     def _stack_once(self, dims, new_dim):
-        if dims == ... or dims == [...]:
+        if list(dims) == [...]:
             dims = self.dims
         variables = {}
         for name, var in self.variables.items():
diff --git a/xarray/tests/test_dataarray.py b/xarray/tests/test_dataarray.py
index 8f2332f9229..3d4bae18f94 100644
--- a/xarray/tests/test_dataarray.py
+++ b/xarray/tests/test_dataarray.py
@@ -2040,7 +2040,7 @@ def test_stack_unstack(self):
         actual = orig.stack(z=["x", "y"]).unstack("z").drop_vars(["x", "y"])
         assert_identical(orig, actual)
 
-        actual = orig.stack(z=...).unstack("z").drop_vars(["x", "y"])
+        actual = orig.stack(z=[...]).unstack("z").drop_vars(["x", "y"])
         assert_identical(orig, actual)
 
         dims = ["a", "b", "c", "d", "e"]
diff --git a/xarray/tests/test_dataset.py b/xarray/tests/test_dataset.py
index 86bd1eb5f31..d789e0c067b 100644
--- a/xarray/tests/test_dataset.py
+++ b/xarray/tests/test_dataset.py
@@ -2871,7 +2871,8 @@ def test_stack(self):
         actual = ds.stack(z=[...])
         assert_identical(expected, actual)
 
-        actual = ds.stack(z=...)
+        # non list dims with ellipsis
+        actual = ds.stack(z=(...,))
         assert_identical(expected, actual)
 
         exp_index = pd.MultiIndex.from_product([["a", "b"], [0, 1]], names=["y", "x"])

From b1b3e909d2014a8a456de7c6ced97149b968dec5 Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Wed, 4 Mar 2020 07:20:21 -0500
Subject: [PATCH 04/10] docs

---
 doc/reshaping.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/reshaping.rst b/doc/reshaping.rst
index 881f841ea72..90a6efe3414 100644
--- a/doc/reshaping.rst
+++ b/doc/reshaping.rst
@@ -113,7 +113,7 @@ As elsewhere in xarray, an ellipsis (`...`) can be used to represent all dimensi
 
 .. ipython:: python
 
-    stacked = array.stack(z=...)
+    stacked = array.stack(z=[...])
     stacked
 
 These methods are modeled on the :py:class:`pandas.DataFrame` methods of the

From d7cac819c83ebae9474e170a4d3a514c1ec833ac Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Wed, 4 Mar 2020 07:27:23 -0500
Subject: [PATCH 05/10] whatsnew

---
 doc/whats-new.rst | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 4a6083522ba..b2bd579beb6 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -36,14 +36,19 @@ New Features
   By `Justus Magin <https://github.com/keewis>`_.
 - :py:meth:`Dataset.groupby` and :py:meth:`DataArray.groupby` now raise a 
   `TypeError` on multiple string arguments. Receiving multiple string arguments
-  often means a user is attempting to pass multiple dimensions to group over
-  and should instead pass a list.
+  often means a user is attempting to pass multiple dimensions as seeparate
+  argument and should instead pass a list.
+  (:pull:`3802`)
   By `Maximilian Roos <https://github.com/max-sixty>`_
 - The new ``Dataset._repr_html_`` and ``DataArray._repr_html_`` (introduced
   in 0.14.1) is now on by default. To disable, use
   ``xarray.set_options(display_style="text")``.
   By `Julia Signell <https://github.com/jsignell>`_.
-
+- An ellipsis (``...``) is now supported in the ``dims`` argument of
+  :py:meth:`Dataset.stack` and :py:meth:`DataArray.stack` to mean all
+  dimensions, similar to its meaning in :py:meth:`DataArray.transpose`
+  (:pull:`3826`)
+  By `Maximilian Roos <https://github.com/max-sixty>`_
 
 Bug fixes
 ~~~~~~~~~

From 134db2d83ce92cac6e43680a92635f3883638de3 Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Wed, 4 Mar 2020 07:36:26 -0500
Subject: [PATCH 06/10] docstring, whatsnew

---
 doc/whats-new.rst        | 6 +++---
 xarray/core/dataarray.py | 3 ++-
 xarray/core/dataset.py   | 3 ++-
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index b2bd579beb6..5eee190f18e 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -36,8 +36,8 @@ New Features
   By `Justus Magin <https://github.com/keewis>`_.
 - :py:meth:`Dataset.groupby` and :py:meth:`DataArray.groupby` now raise a 
   `TypeError` on multiple string arguments. Receiving multiple string arguments
-  often means a user is attempting to pass multiple dimensions as seeparate
-  argument and should instead pass a list.
+  often means a user is attempting to pass multiple dimensions as separate
+  arguments and should instead pass a single list of dimensions.
   (:pull:`3802`)
   By `Maximilian Roos <https://github.com/max-sixty>`_
 - The new ``Dataset._repr_html_`` and ``DataArray._repr_html_`` (introduced
@@ -45,7 +45,7 @@ New Features
   ``xarray.set_options(display_style="text")``.
   By `Julia Signell <https://github.com/jsignell>`_.
 - An ellipsis (``...``) is now supported in the ``dims`` argument of
-  :py:meth:`Dataset.stack` and :py:meth:`DataArray.stack` to mean all
+  :py:meth:`Dataset.stack` and :py:meth:`DataArray.stack`, meaning all
   dimensions, similar to its meaning in :py:meth:`DataArray.transpose`
   (:pull:`3826`)
   By `Maximilian Roos <https://github.com/max-sixty>`_
diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index b1da0ca1448..0c9baefdad7 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -1705,7 +1705,8 @@ def stack(
         ----------
         dimensions : Mapping of the form new_name=(dim1, dim2, ...)
             Names of new dimensions, and the existing dimensions that they
-            replace.
+            replace. Passing a list with an ellipsis (`[...]`) will stack over all
+            dimensions.
         **dimensions_kwargs:
             The keyword arguments form of ``dimensions``.
             One of dimensions or dimensions_kwargs must be provided.
diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 51debd1e61d..2c0b609d796 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -3279,7 +3279,8 @@ def stack(
         ----------
         dimensions : Mapping of the form new_name=(dim1, dim2, ...)
             Names of new dimensions, and the existing dimensions that they
-            replace.
+            replace. Passing a list with an ellipsis (`[...]`) will stack over all
+            dimensions.
         **dimensions_kwargs:
             The keyword arguments form of ``dimensions``.
             One of dimensions or dimensions_kwargs must be provided.

From ae18a7aa050d698b1ed2e9a0afce4fe646b4a67d Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Wed, 4 Mar 2020 07:40:21 -0500
Subject: [PATCH 07/10] docstring, whatsnew

---
 doc/whats-new.rst        | 2 +-
 xarray/core/dataarray.py | 4 ++--
 xarray/core/dataset.py   | 4 ++--
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 5eee190f18e..9be349f0173 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -46,7 +46,7 @@ New Features
   By `Julia Signell <https://github.com/jsignell>`_.
 - An ellipsis (``...``) is now supported in the ``dims`` argument of
   :py:meth:`Dataset.stack` and :py:meth:`DataArray.stack`, meaning all
-  dimensions, similar to its meaning in :py:meth:`DataArray.transpose`
+  dimensions, similar to its meaning in :py:meth:`DataArray.transpose`.
   (:pull:`3826`)
   By `Maximilian Roos <https://github.com/max-sixty>`_
 
diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index 0c9baefdad7..474ab1d206d 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -1705,8 +1705,8 @@ def stack(
         ----------
         dimensions : Mapping of the form new_name=(dim1, dim2, ...)
             Names of new dimensions, and the existing dimensions that they
-            replace. Passing a list with an ellipsis (`[...]`) will stack over all
-            dimensions.
+            replace. Passing a list with an ellipsis (`[...]`) as existing
+            dimensions will stack over all dimensions.
         **dimensions_kwargs:
             The keyword arguments form of ``dimensions``.
             One of dimensions or dimensions_kwargs must be provided.
diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 2c0b609d796..00e3e45fd59 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -3279,8 +3279,8 @@ def stack(
         ----------
         dimensions : Mapping of the form new_name=(dim1, dim2, ...)
             Names of new dimensions, and the existing dimensions that they
-            replace. Passing a list with an ellipsis (`[...]`) will stack over all
-            dimensions.
+            replace. Passing a list with an ellipsis (`[...]`) as existing
+            dimensions will stack over all dimensions.
         **dimensions_kwargs:
             The keyword arguments form of ``dimensions``.
             One of dimensions or dimensions_kwargs must be provided.

From a9458f86baff2353272f74e32177c30a880e92bf Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Fri, 6 Mar 2020 01:26:07 -0500
Subject: [PATCH 08/10] add passing a partial list of dims

---
 xarray/core/dataarray.py     | 2 +-
 xarray/core/dataset.py       | 7 ++++---
 xarray/tests/test_dataset.py | 4 ++++
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index 474ab1d206d..b8c5a4e27b3 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -1705,7 +1705,7 @@ def stack(
         ----------
         dimensions : Mapping of the form new_name=(dim1, dim2, ...)
             Names of new dimensions, and the existing dimensions that they
-            replace. Passing a list with an ellipsis (`[...]`) as existing
+            replace. Passing a list containing an ellipsis (`[...]`)
             dimensions will stack over all dimensions.
         **dimensions_kwargs:
             The keyword arguments form of ``dimensions``.
diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 00e3e45fd59..b7edc7e8be3 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -86,6 +86,7 @@
     decode_numpy_dict_values,
     either_dict_or_kwargs,
     hashable,
+    infix_dims,
     is_dict_like,
     is_scalar,
     maybe_wrap_array,
@@ -3235,8 +3236,8 @@ def reorder_levels(
         return self._replace(variables, indexes=indexes)
 
     def _stack_once(self, dims, new_dim):
-        if list(dims) == [...]:
-            dims = self.dims
+        if ... in dims:
+            dims = list(infix_dims(dims, self.dims))
         variables = {}
         for name, var in self.variables.items():
             if name not in dims:
@@ -3279,7 +3280,7 @@ def stack(
         ----------
         dimensions : Mapping of the form new_name=(dim1, dim2, ...)
             Names of new dimensions, and the existing dimensions that they
-            replace. Passing a list with an ellipsis (`[...]`) as existing
+            replace. Passing a list containing an ellipsis (`[...]`)
             dimensions will stack over all dimensions.
         **dimensions_kwargs:
             The keyword arguments form of ``dimensions``.
diff --git a/xarray/tests/test_dataset.py b/xarray/tests/test_dataset.py
index d789e0c067b..ae10abf44f3 100644
--- a/xarray/tests/test_dataset.py
+++ b/xarray/tests/test_dataset.py
@@ -2875,6 +2875,10 @@ def test_stack(self):
         actual = ds.stack(z=(...,))
         assert_identical(expected, actual)
 
+        # ellipsis with given dim
+        actual = ds.stack(z=[..., "y"])
+        assert_identical(expected, actual)
+
         exp_index = pd.MultiIndex.from_product([["a", "b"], [0, 1]], names=["y", "x"])
         expected = Dataset(
             {"a": ("z", [0, 1, 0, 1]), "b": ("z", [0, 2, 1, 3]), "z": exp_index}

From 4555f52372d4880328c16f1f9f424db82b353ac6 Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Thu, 19 Mar 2020 15:26:08 -0400
Subject: [PATCH 09/10] more wording changes

---
 doc/reshaping.rst        | 4 ++--
 doc/whats-new.rst        | 2 +-
 xarray/core/dataarray.py | 3 +--
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/doc/reshaping.rst b/doc/reshaping.rst
index 90a6efe3414..465ca14dfc2 100644
--- a/doc/reshaping.rst
+++ b/doc/reshaping.rst
@@ -109,11 +109,11 @@ implemented :py:meth:`~xarray.DataArray.stack` and
     stacked
     stacked.unstack('z')
 
-As elsewhere in xarray, an ellipsis (`...`) can be used to represent all dimensions:
+As elsewhere in xarray, an ellipsis (`...`) can be used to represent all unlisted dimensions:
 
 .. ipython:: python
 
-    stacked = array.stack(z=[...])
+    stacked = array.stack(z=[..., "x"])
     stacked
 
 These methods are modeled on the :py:class:`pandas.DataFrame` methods of the
diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 6517c64ee1c..6082079870f 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -46,7 +46,7 @@ New Features
   By `Julia Signell <https://github.com/jsignell>`_.
 - An ellipsis (``...``) is now supported in the ``dims`` argument of
   :py:meth:`Dataset.stack` and :py:meth:`DataArray.stack`, meaning all
-  dimensions, similar to its meaning in :py:meth:`DataArray.transpose`.
+  unlisted dimensions, similar to its meaning in :py:meth:`DataArray.transpose`.
   (:pull:`3826`)
   By `Maximilian Roos <https://github.com/max-sixty>`_
 - :py:meth:`Dataset.where` and :py:meth:`DataArray.where` accept a lambda as a
diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index 0ded38fd81d..686074f5550 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -1707,8 +1707,7 @@ def stack(
         ----------
         dimensions : Mapping of the form new_name=(dim1, dim2, ...)
             Names of new dimensions, and the existing dimensions that they
-            replace. Passing a list containing an ellipsis (`[...]`)
-            dimensions will stack over all dimensions.
+            replace. An ellipsis (`...`) will be replaced by all unlisted dimensions.
         **dimensions_kwargs:
             The keyword arguments form of ``dimensions``.
             One of dimensions or dimensions_kwargs must be provided.

From ab68943aec83b91c77774460de83090db7466a28 Mon Sep 17 00:00:00 2001
From: Maximilian Roos <m@maxroos.com>
Date: Thu, 19 Mar 2020 17:34:10 -0400
Subject: [PATCH 10/10] improvement from @dcherian

---
 xarray/core/dataarray.py | 2 ++
 xarray/core/dataset.py   | 5 +++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index 86eebf28ea9..324e7ccd290 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -1710,6 +1710,8 @@ def stack(
         dimensions : Mapping of the form new_name=(dim1, dim2, ...)
             Names of new dimensions, and the existing dimensions that they
             replace. An ellipsis (`...`) will be replaced by all unlisted dimensions.
+            Passing a list containing an ellipsis (`stacked_dim=[...]`) will stack over
+            all dimensions.
         **dimensions_kwargs:
             The keyword arguments form of ``dimensions``.
             One of dimensions or dimensions_kwargs must be provided.
diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index be03ba9c4ea..4a369b9aa81 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -3307,8 +3307,9 @@ def stack(
         ----------
         dimensions : Mapping of the form new_name=(dim1, dim2, ...)
             Names of new dimensions, and the existing dimensions that they
-            replace. Passing a list containing an ellipsis (`[...]`)
-            dimensions will stack over all dimensions.
+            replace. An ellipsis (`...`) will be replaced by all unlisted dimensions.
+            Passing a list containing an ellipsis (`stacked_dim=[...]`) will stack over
+            all dimensions.
         **dimensions_kwargs:
             The keyword arguments form of ``dimensions``.
             One of dimensions or dimensions_kwargs must be provided.