Add inclusive argument to cftime_range and date_range and deprecate closed argument

doc/whats-new.rst

@@ -45,7 +45,10 @@ Breaking changes
 
 Deprecations
 ~~~~~~~~~~~~
-
+- Following pandas, the `closed` parameters of :py:func:`cftime_range` and
+  :py:func:`date_range` are deprecated in favor of the `inclusive` parameters,
+  and will be removed in a future version of xarray (:issue:`6985`:,
+  :pull:`7373`).  By `Spencer Clark <https://github.com/spencerkclark>`_.
 
 Bug fixes
 ~~~~~~~~~

xarray/coding/cftime_offsets.py

@@ -44,7 +44,7 @@
 import re
 from datetime import datetime, timedelta
 from functools import partial
-from typing import ClassVar
+from typing import TYPE_CHECKING, ClassVar
 
 import numpy as np
 import pandas as pd
@@ -57,14 +57,19 @@
     format_cftime_datetime,
 )
 from xarray.core.common import _contains_datetime_like_objects, is_np_datetime_like
-from xarray.core.pdcompat import count_not_none
+from xarray.core.pdcompat import NoDefault, count_not_none, no_default
+from xarray.core.utils import emit_user_level_warning
 
 try:
     import cftime
 except ImportError:
     cftime = None
 
 
+if TYPE_CHECKING:
+    from xarray.core.types import InclusiveOptions, SideOptions
+
+
 def get_date_type(calendar, use_cftime=True):
     """Return the cftime date type for a given calendar name."""
     if cftime is None:
@@ -849,14 +854,49 @@ def _generate_range(start, end, periods, offset):
             current = next_date
 
 
+def _translate_closed_to_inclusive(closed):
+    """Follows code added in pandas #43504."""
+    emit_user_level_warning(
+        "Following pandas, the `closed` parameter is deprecated in "
+        "favor of the `inclusive` parameter, and will be removed in "
+        "a future version of xarray.",
+        FutureWarning,
+    )
+    if closed is None:
+        inclusive = "both"
+    elif closed in ("left", "right"):
+        inclusive = closed
+    else:
+        raise ValueError(
+            f"Argument `closed` must be either 'left', 'right', or None. "
+            f"Got {closed!r}."
+        )
+    return inclusive
+
+
+def _infer_inclusive(closed, inclusive):
+    """Follows code added in pandas #43504."""
+    if closed is not no_default and inclusive is not None:
+        raise ValueError(
+            "Following pandas, deprecated argument `closed` cannot be "
+            "passed if argument `inclusive` is not None."
+        )
+    if closed is not no_default:
+        inclusive = _translate_closed_to_inclusive(closed)
+    elif inclusive is None:
+        inclusive = "both"
+    return inclusive
+
+
 def cftime_range(
     start=None,
     end=None,
     periods=None,
     freq="D",
     normalize=False,
     name=None,
-    closed=None,
+    closed: NoDefault | SideOptions = no_default,
+    inclusive: None | InclusiveOptions = None,
     calendar="standard",
 ):
     """Return a fixed frequency CFTimeIndex.
@@ -875,9 +915,20 @@ def cftime_range(
         Normalize start/end dates to midnight before generating date range.
     name : str, default: None
         Name of the resulting index
-    closed : {"left", "right"} or None, default: None
+    closed : {None, "left", "right"}, default: "NO_DEFAULT"
         Make the interval closed with respect to the given frequency to the
         "left", "right", or both sides (None).
+
+        .. deprecated:: 2023.01.1
+            Following pandas, the ``closed`` parameter is deprecated in favor
+            of the ``inclusive`` parameter, and will be removed in a future
+            version of xarray.
+
+    inclusive : {None, "both", "neither", "left", "right"}, default None
+        Include boundaries; whether to set each bound as closed or open.
+
+        .. versionadded:: 2023.01.1
+
     calendar : str, default: "standard"
         Calendar type for the datetimes.
 
@@ -1047,18 +1098,25 @@ def cftime_range(
         offset = to_offset(freq)
         dates = np.array(list(_generate_range(start, end, periods, offset)))
 
-    left_closed = False
-    right_closed = False
+    inclusive = _infer_inclusive(closed, inclusive)
 
-    if closed is None:
+    if inclusive == "neither":
+        left_closed = False
+        right_closed = False
+    elif inclusive == "left":
         left_closed = True
+        right_closed = False
+    elif inclusive == "right":
+        left_closed = False
         right_closed = True
-    elif closed == "left":
+    elif inclusive == "both":
         left_closed = True
-    elif closed == "right":
         right_closed = True
     else:
-        raise ValueError("Closed must be either 'left', 'right' or None")
+        raise ValueError(
+            f"Argument `inclusive` must be either 'both', 'neither', "
+            f"'left', 'right', or None.  Got {inclusive}."
+        )
 
     if not left_closed and len(dates) and start is not None and dates[0] == start:
         dates = dates[1:]
@@ -1076,7 +1134,8 @@ def date_range(
     tz=None,
     normalize=False,
     name=None,
-    closed=None,
+    closed: NoDefault | SideOptions = no_default,
+    inclusive: None | InclusiveOptions = None,
     calendar="standard",
     use_cftime=None,
 ):
@@ -1103,9 +1162,20 @@ def date_range(
         Normalize start/end dates to midnight before generating date range.
     name : str, default: None
         Name of the resulting index
-    closed : {"left", "right"} or None, default: None
+    closed : {None, "left", "right"}, default: "NO_DEFAULT"
         Make the interval closed with respect to the given frequency to the
         "left", "right", or both sides (None).
+
+        .. deprecated:: 2023.01.1
+            Following pandas, the `closed` parameter is deprecated in favor
+            of the `inclusive` parameter, and will be removed in a future
+            version of xarray.
+
+    inclusive : {None, "both", "neither", "left", "right"}, default: None
+        Include boundaries; whether to set each bound as closed or open.
+
+        .. versionadded:: 2023.01.1
+
     calendar : str, default: "standard"
         Calendar type for the datetimes.
     use_cftime : boolean, optional
@@ -1129,6 +1199,8 @@ def date_range(
     if tz is not None:
         use_cftime = False
 
+    inclusive = _infer_inclusive(closed, inclusive)
+
     if _is_standard_calendar(calendar) and use_cftime is not True:
         try:
             return pd.date_range(
@@ -1139,7 +1211,7 @@ def date_range(
                 tz=tz,
                 normalize=normalize,
                 name=name,
-                closed=closed,
+                inclusive=inclusive,
             )
         except pd.errors.OutOfBoundsDatetime as err:
             if use_cftime is False:
@@ -1158,7 +1230,7 @@ def date_range(
         freq=freq,
         normalize=normalize,
         name=name,
-        closed=closed,
+        inclusive=inclusive,
         calendar=calendar,
     )
 

xarray/core/pdcompat.py

@@ -35,10 +35,36 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 from __future__ import annotations
 
+from enum import Enum
+from typing import Literal
+
 
 def count_not_none(*args) -> int:
     """Compute the number of non-None arguments.
 
     Copied from pandas.core.common.count_not_none (not part of the public API)
     """
     return sum(arg is not None for arg in args)
+
+
+class _NoDefault(Enum):
+    """Used by pandas to specify a default value for a deprecated argument.
+    Copied from pandas._libs.lib._NoDefault.
+
+    See also:
+    - pandas-dev/pandas#30788
+    - pandas-dev/pandas#40684
+    - pandas-dev/pandas#40715
+    - pandas-dev/pandas#47045
+    """
+
+    no_default = "NO_DEFAULT"
+
+    def __repr__(self) -> str:
+        return "<no_default>"
+
+
+no_default = (
+    _NoDefault.no_default
+)  # Sentinel indicating the default value following pandas
+NoDefault = Literal[_NoDefault.no_default]  # For typing following pandas

xarray/core/types.py

@@ -168,6 +168,7 @@ def dtype(self) -> np.dtype:
 
 CoarsenBoundaryOptions = Literal["exact", "trim", "pad"]
 SideOptions = Literal["left", "right"]
+InclusiveOptions = Literal["both", "neither", "left", "right"]
 
 ScaleOptions = Literal["linear", "symlog", "log", "logit", None]
 HueStyleOptions = Literal["continuous", "discrete", None]