From 583dd95b2d4e37ca334d8e9bd37dcc0745767275 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 3 Nov 2023 01:00:54 +0100
Subject: [PATCH 01/13] Update _array_api.py

---
 xarray/namedarray/_array_api.py | 49 +++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/xarray/namedarray/_array_api.py b/xarray/namedarray/_array_api.py
index e205c4d4efe..fb74fb6cfeb 100644
--- a/xarray/namedarray/_array_api.py
+++ b/xarray/namedarray/_array_api.py
@@ -8,11 +8,13 @@
 
 from xarray.namedarray._typing import (
     _arrayapi,
+    _Dim,
     _DType,
     _ScalarType,
     _ShapeType,
     _SupportsImag,
     _SupportsReal,
+    Default,
 )
 from xarray.namedarray.core import NamedArray
 
@@ -144,3 +146,50 @@ def real(
     xp = _get_data_namespace(x)
     out = x._new(data=xp.real(x._data))
     return out
+
+
+# %% Manipulation functions
+def expand_dims(
+    x: NamedArray[Any, _DType],
+    /,
+    *,
+    dim: _Dim | Default = _default,
+    axis: _Axis = 0,
+) -> NamedArray[Any, _DType]:
+    """
+    Expands the shape of an array by inserting a new dimension of size one at the
+    position specified by dims.
+
+    Parameters
+    ----------
+    x :
+        Array to expand.
+    dim :
+        Dimension name. New dimension will be stored in the 0 position.
+    axis :
+        Axis position (zero-based). If x has rank (i.e, number of dimensions) N,
+        a valid axis must reside on the closed-interval [-N-1, N]. If provided a
+        negative axis, the axis position at which to insert a singleton dimension
+        must be computed as N + axis + 1. Hence, if provided -1, the resolved axis
+        position must be N (i.e., a singleton dimension must be appended to the
+        input array x). If provided -N-1, the resolved axis position must be 0
+        (i.e., a singleton dimension must be prepended to the input array x).
+
+    Returns
+    -------
+        out :
+            An expanded output array having the same data type as x.
+
+    Examples
+    --------
+    >>> x = NamedArray(("x", "y"), nxp.asarray([[1.0, 2.0], [3.0, 4.0]]))
+    >>> expand_dims(x, dims="new_dim")
+    <xarray.NamedArray (new_dim: 1, x: 2, y: 2)>
+    Array([[[1., 2.],
+            [3., 4.]]], dtype=float64)
+    """
+    xp = _get_data_namespace(x)
+    d = list(x.dims)
+    d.insert(axis, dim)
+    out = x._new(dims=tuple(d), data=xp.expand_dims(x._data, axis=axis))
+    return out

From eb313fd9b161a0ff7dd967438a7c40392780836a Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 3 Nov 2023 00:01:57 +0000
Subject: [PATCH 02/13] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 xarray/namedarray/_array_api.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/namedarray/_array_api.py b/xarray/namedarray/_array_api.py
index fb74fb6cfeb..13919f1f4d2 100644
--- a/xarray/namedarray/_array_api.py
+++ b/xarray/namedarray/_array_api.py
@@ -7,6 +7,7 @@
 import numpy as np
 
 from xarray.namedarray._typing import (
+    Default,
     _arrayapi,
     _Dim,
     _DType,
@@ -14,7 +15,6 @@
     _ShapeType,
     _SupportsImag,
     _SupportsReal,
-    Default,
 )
 from xarray.namedarray.core import NamedArray
 

From 23fcb2d81ae94212bce4632c7b8e2c8c36829a69 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 3 Nov 2023 16:21:10 +0100
Subject: [PATCH 03/13] fixes

---
 xarray/namedarray/_array_api.py |  4 ++++
 xarray/namedarray/_typing.py    | 10 ++++++++++
 2 files changed, 14 insertions(+)

diff --git a/xarray/namedarray/_array_api.py b/xarray/namedarray/_array_api.py
index 13919f1f4d2..9fb4ca46fb1 100644
--- a/xarray/namedarray/_array_api.py
+++ b/xarray/namedarray/_array_api.py
@@ -9,7 +9,11 @@
 from xarray.namedarray._typing import (
     Default,
     _arrayapi,
+    _Axis,
+    _AxisLike,
+    _default,
     _Dim,
+    _Dims,
     _DType,
     _ScalarType,
     _ShapeType,
diff --git a/xarray/namedarray/_typing.py b/xarray/namedarray/_typing.py
index 0b972e19539..de60b8ca7cf 100644
--- a/xarray/namedarray/_typing.py
+++ b/xarray/namedarray/_typing.py
@@ -1,10 +1,12 @@
 from __future__ import annotations
 
 from collections.abc import Hashable, Iterable, Mapping, Sequence
+from enum import Enum
 from types import ModuleType
 from typing import (
     Any,
     Callable,
+    Final,
     Protocol,
     SupportsIndex,
     TypeVar,
@@ -15,6 +17,14 @@
 
 import numpy as np
 
+
+# Singleton type, as per https://github.com/python/typing/pull/240
+class Default(Enum):
+    token: Final = 0
+
+
+_default = Default.token
+
 # https://stackoverflow.com/questions/74633074/how-to-type-hint-a-generic-numpy-array
 _T = TypeVar("_T")
 _T_co = TypeVar("_T_co", covariant=True)

From 530aedf4eebcc1e120abde2032bb45a5b60b54f1 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 3 Nov 2023 15:21:52 +0000
Subject: [PATCH 04/13] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 xarray/namedarray/_array_api.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/xarray/namedarray/_array_api.py b/xarray/namedarray/_array_api.py
index 9fb4ca46fb1..d6aeebb0632 100644
--- a/xarray/namedarray/_array_api.py
+++ b/xarray/namedarray/_array_api.py
@@ -10,10 +10,8 @@
     Default,
     _arrayapi,
     _Axis,
-    _AxisLike,
     _default,
     _Dim,
-    _Dims,
     _DType,
     _ScalarType,
     _ShapeType,

From 7205a32da5cb292eed754126b021b90a42c28b6e Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 3 Nov 2023 16:22:59 +0100
Subject: [PATCH 05/13] more

---
 xarray/namedarray/core.py  |  3 ++-
 xarray/namedarray/utils.py | 15 +--------------
 2 files changed, 3 insertions(+), 15 deletions(-)

diff --git a/xarray/namedarray/core.py b/xarray/namedarray/core.py
index 2fef1cad3db..126e0b8b5e3 100644
--- a/xarray/namedarray/core.py
+++ b/xarray/namedarray/core.py
@@ -25,6 +25,7 @@
     _arrayapi,
     _arrayfunction_or_api,
     _chunkedarray,
+    _default,
     _dtype,
     _DType_co,
     _ScalarType_co,
@@ -33,7 +34,7 @@
     _SupportsImag,
     _SupportsReal,
 )
-from xarray.namedarray.utils import _default, is_duck_dask_array, to_0d_object_array
+from xarray.namedarray.utils import is_duck_dask_array, to_0d_object_array
 
 if TYPE_CHECKING:
     from numpy.typing import ArrayLike, NDArray
diff --git a/xarray/namedarray/utils.py b/xarray/namedarray/utils.py
index 03eb0134231..4bd20931189 100644
--- a/xarray/namedarray/utils.py
+++ b/xarray/namedarray/utils.py
@@ -2,12 +2,7 @@
 
 import sys
 from collections.abc import Hashable
-from enum import Enum
-from typing import (
-    TYPE_CHECKING,
-    Any,
-    Final,
-)
+from typing import TYPE_CHECKING, Any
 
 import numpy as np
 
@@ -31,14 +26,6 @@
         DaskCollection: Any = NDArray  # type: ignore
 
 
-# Singleton type, as per https://github.com/python/typing/pull/240
-class Default(Enum):
-    token: Final = 0
-
-
-_default = Default.token
-
-
 def module_available(module: str) -> bool:
     """Checks whether a module is installed without importing it.
 

From a204fe5edd89b9c392934b3910dd7a697b2436d4 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 3 Nov 2023 16:42:24 +0100
Subject: [PATCH 06/13] fixes

---
 xarray/namedarray/_array_api.py | 31 +++++++++++++++++++------------
 xarray/namedarray/_typing.py    |  4 ++++
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/xarray/namedarray/_array_api.py b/xarray/namedarray/_array_api.py
index d6aeebb0632..7f1fce08c9e 100644
--- a/xarray/namedarray/_array_api.py
+++ b/xarray/namedarray/_array_api.py
@@ -9,8 +9,8 @@
 from xarray.namedarray._typing import (
     Default,
     _arrayapi,
-    _Axis,
     _default,
+    _Axis,
     _Dim,
     _DType,
     _ScalarType,
@@ -167,15 +167,9 @@ def expand_dims(
     x :
         Array to expand.
     dim :
-        Dimension name. New dimension will be stored in the 0 position.
+        Dimension name. New dimension will be stored in the axis position.
     axis :
-        Axis position (zero-based). If x has rank (i.e, number of dimensions) N,
-        a valid axis must reside on the closed-interval [-N-1, N]. If provided a
-        negative axis, the axis position at which to insert a singleton dimension
-        must be computed as N + axis + 1. Hence, if provided -1, the resolved axis
-        position must be N (i.e., a singleton dimension must be appended to the
-        input array x). If provided -N-1, the resolved axis position must be 0
-        (i.e., a singleton dimension must be prepended to the input array x).
+        (Not recommended) Axis position (zero-based). Default is 0.
 
     Returns
     -------
@@ -185,13 +179,26 @@ def expand_dims(
     Examples
     --------
     >>> x = NamedArray(("x", "y"), nxp.asarray([[1.0, 2.0], [3.0, 4.0]]))
-    >>> expand_dims(x, dims="new_dim")
-    <xarray.NamedArray (new_dim: 1, x: 2, y: 2)>
+    >>> expand_dims(x)
+    <xarray.NamedArray (dim_2: 1, x: 2, y: 2)>
+    Array([[[1., 2.],
+            [3., 4.]]], dtype=float64)
+    >>> expand_dims(x, dim="z")
+    <xarray.NamedArray (z: 1, x: 2, y: 2)>
     Array([[[1., 2.],
             [3., 4.]]], dtype=float64)
     """
     xp = _get_data_namespace(x)
-    d = list(x.dims)
+    dims = x.dims
+    if dim is _default:
+        dim = f"dim_{len(dims)}"
+    d = list(dims)
     d.insert(axis, dim)
     out = x._new(dims=tuple(d), data=xp.expand_dims(x._data, axis=axis))
     return out
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
diff --git a/xarray/namedarray/_typing.py b/xarray/namedarray/_typing.py
index de60b8ca7cf..670a2076eb1 100644
--- a/xarray/namedarray/_typing.py
+++ b/xarray/namedarray/_typing.py
@@ -59,6 +59,10 @@ def dtype(self) -> _DType_co:
 _ShapeType = TypeVar("_ShapeType", bound=Any)
 _ShapeType_co = TypeVar("_ShapeType_co", bound=Any, covariant=True)
 
+_Axis = int
+_Axes = tuple[_Axis, ...]
+_AxisLike = Union[_Axis, _Axes]
+
 _Chunks = tuple[_Shape, ...]
 
 _Dim = Hashable

From 11fee3995fa4d1666ec65a138388d279a39635b2 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 3 Nov 2023 15:45:03 +0000
Subject: [PATCH 07/13] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 xarray/namedarray/_array_api.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/namedarray/_array_api.py b/xarray/namedarray/_array_api.py
index 7f1fce08c9e..738b21664d8 100644
--- a/xarray/namedarray/_array_api.py
+++ b/xarray/namedarray/_array_api.py
@@ -9,8 +9,8 @@
 from xarray.namedarray._typing import (
     Default,
     _arrayapi,
-    _default,
     _Axis,
+    _default,
     _Dim,
     _DType,
     _ScalarType,

From ae921480b2a1b72872d37e9c4c3307d38bc678b2 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 3 Nov 2023 16:51:03 +0100
Subject: [PATCH 08/13] Update test_namedarray.py

---
 xarray/tests/test_namedarray.py | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/xarray/tests/test_namedarray.py b/xarray/tests/test_namedarray.py
index 448e8cf819a..0603fd49ccc 100644
--- a/xarray/tests/test_namedarray.py
+++ b/xarray/tests/test_namedarray.py
@@ -9,9 +9,13 @@
 import pytest
 
 from xarray.core.indexing import ExplicitlyIndexed
-from xarray.namedarray._typing import _arrayfunction_or_api, _DType_co, _ShapeType_co
+from xarray.namedarray._typing import (
+    _default,
+    _arrayfunction_or_api,
+    _DType_co,
+    _ShapeType_co,
+)
 from xarray.namedarray.core import NamedArray, from_array
-from xarray.namedarray.utils import _default
 
 if TYPE_CHECKING:
     from types import ModuleType
@@ -24,8 +28,8 @@
         _DType,
         _Shape,
         duckarray,
+        Default,
     )
-    from xarray.namedarray.utils import Default
 
 
 class CustomArrayBase(Generic[_ShapeType_co, _DType_co]):

From 5acf75aa65c17676545beaaf9d09c25de6bd72eb Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 3 Nov 2023 15:52:00 +0000
Subject: [PATCH 09/13] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 xarray/tests/test_namedarray.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xarray/tests/test_namedarray.py b/xarray/tests/test_namedarray.py
index 0603fd49ccc..82110e072b2 100644
--- a/xarray/tests/test_namedarray.py
+++ b/xarray/tests/test_namedarray.py
@@ -10,8 +10,8 @@
 
 from xarray.core.indexing import ExplicitlyIndexed
 from xarray.namedarray._typing import (
-    _default,
     _arrayfunction_or_api,
+    _default,
     _DType_co,
     _ShapeType_co,
 )
@@ -23,12 +23,12 @@
     from numpy.typing import ArrayLike, DTypeLike, NDArray
 
     from xarray.namedarray._typing import (
+        Default,
         _AttrsLike,
         _DimsLike,
         _DType,
         _Shape,
         duckarray,
-        Default,
     )
 
 

From 6e28051d0b9d7ba3411754d6678f2857c3b97159 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 3 Nov 2023 16:55:24 +0100
Subject: [PATCH 10/13] Update _array_api.py

---
 xarray/namedarray/_array_api.py | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/xarray/namedarray/_array_api.py b/xarray/namedarray/_array_api.py
index 738b21664d8..b5c320e0b96 100644
--- a/xarray/namedarray/_array_api.py
+++ b/xarray/namedarray/_array_api.py
@@ -196,9 +196,3 @@ def expand_dims(
     d.insert(axis, dim)
     out = x._new(dims=tuple(d), data=xp.expand_dims(x._data, axis=axis))
     return out
-
-
-if __name__ == "__main__":
-    import doctest
-
-    doctest.testmod()

From 66f82b171437429d8956104bcf1cf36a0c84a0a3 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 3 Nov 2023 17:07:33 +0100
Subject: [PATCH 11/13] Update variable.py

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

diff --git a/xarray/core/variable.py b/xarray/core/variable.py
index db109a40454..d1b387eb8b4 100644
--- a/xarray/core/variable.py
+++ b/xarray/core/variable.py
@@ -2599,7 +2599,7 @@ def _as_sparse(self, sparse_format=_default, fill_value=_default) -> Variable:
         """
         Use sparse-array as backend.
         """
-        from xarray.namedarray.utils import _default as _default_named
+        from xarray.namedarray._typing import _default as _default_named
 
         if sparse_format is _default:
             sparse_format = _default_named

From 3deb66c17a1bb9b641049767cb8395074a6b6591 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 3 Nov 2023 17:12:52 +0100
Subject: [PATCH 12/13] Update core.py

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

diff --git a/xarray/namedarray/core.py b/xarray/namedarray/core.py
index 126e0b8b5e3..00a18dfb353 100644
--- a/xarray/namedarray/core.py
+++ b/xarray/namedarray/core.py
@@ -53,8 +53,8 @@
         _Shape,
         _ShapeType,
         duckarray,
+        Default,
     )
-    from xarray.namedarray.utils import Default
 
     try:
         from dask.typing import (

From 84e0f143753422df09ade814162c9971e7ee06d8 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 3 Nov 2023 16:15:55 +0000
Subject: [PATCH 13/13] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 xarray/namedarray/core.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/namedarray/core.py b/xarray/namedarray/core.py
index b42a7688d3b..9c208bdefcc 100644
--- a/xarray/namedarray/core.py
+++ b/xarray/namedarray/core.py
@@ -41,6 +41,7 @@
 
     from xarray.core.types import Dims
     from xarray.namedarray._typing import (
+        Default,
         _AttrsLike,
         _Chunks,
         _Dim,
@@ -52,7 +53,6 @@
         _Shape,
         _ShapeType,
         duckarray,
-        Default,
     )
 
     try: