DOC: Adjust whatsnew (#56300)

* DOC: Adjust whatsnew

* Update doc/source/whatsnew/v2.2.0.rst

Co-authored-by: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>

* Update doc/source/whatsnew/v2.2.0.rst

Co-authored-by: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>

* Update doc/source/whatsnew/v2.2.0.rst

Co-authored-by: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>

* Update v2.2.0.rst

* Update v2.2.0.rst

---------

Co-authored-by: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>

Author: phofl

doc/source/whatsnew/v2.2.0.rst

@@ -110,7 +110,7 @@ documentation.
 ExtensionArray.to_numpy converts to suitable NumPy dtype
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-:meth:`ExtensionArray.to_numpy`` will now convert to a suitable NumPy dtype instead
+:meth:`ExtensionArray.to_numpy` will now convert to a suitable NumPy dtype instead
 of ``object`` dtype for nullable extension dtypes.
 
 *Old behavior:*
@@ -138,8 +138,8 @@ The default NumPy dtype (without any arguments) is determined as follows:
 
 .. _whatsnew_220.enhancements.struct_accessor:
 
-Series.struct accessor to with PyArrow structured data
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Series.struct accessor for PyArrow structured data
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 The ``Series.struct`` accessor provides attributes and methods for processing
 data with ``struct[pyarrow]`` dtype Series. For example,
@@ -192,7 +192,7 @@ a Series. (:issue:`55323`)
 .. _whatsnew_220.enhancements.calamine:
 
 Calamine engine for :func:`read_excel`
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 The ``calamine`` engine was added to :func:`read_excel`.
 It uses ``python-calamine``, which provides Python bindings for the Rust library `calamine <https://crates.io/crates/calamine>`__.
@@ -216,7 +216,7 @@ For more, see :ref:`io.calamine` in the user guide on IO tools.
 Other enhancements
 ^^^^^^^^^^^^^^^^^^
 
-- :meth:`to_sql` with method parameter set to ``multi`` works with Oracle on the backend
+- :meth:`~DataFrame.to_sql` with method parameter set to ``multi`` works with Oracle on the backend
 - :attr:`Series.attrs` / :attr:`DataFrame.attrs` now uses a deepcopy for propagating ``attrs`` (:issue:`54134`).
 - :func:`read_csv` now supports ``on_bad_lines`` parameter with ``engine="pyarrow"``. (:issue:`54480`)
 - :func:`read_spss` now returns a :class:`DataFrame` that stores the metadata in :attr:`DataFrame.attrs`. (:issue:`54264`)
@@ -387,6 +387,33 @@ For example:
 
     pd.date_range('2020-01-01', periods=3, freq='QE-NOV')
 
+Deprecated automatic downcasting
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Deprecated the automatic downcasting of object dtype results in a number of
+methods. These would silently change the dtype in a hard to predict manner since the
+behavior was value dependent. Additionally, pandas is moving away from silent dtype
+changes (:issue:`54710`, :issue:`54261`).
+
+These methods are:
+
+- :meth:`Series.replace` and :meth:`DataFrame.replace`
+- :meth:`DataFrame.fillna`, :meth:`Series.fillna`
+- :meth:`DataFrame.ffill`, :meth:`Series.ffill`
+- :meth:`DataFrame.bfill`, :meth:`Series.bfill`
+
+Explicitly call :meth:`DataFrame.infer_objects` to replicate the current behavior in the future.
+
+.. code-block:: ipython
+
+    result = result.infer_objects(copy=False)
+
+Set the following option to opt into the future behavior:
+
+.. code-block:: ipython
+
+    In [9]: pd.set_option("future.no_silent_downcasting", True)
+
 Other Deprecations
 ^^^^^^^^^^^^^^^^^^
 - Changed :meth:`Timedelta.resolution_string` to return ``h``, ``min``, ``s``, ``ms``, ``us``, and ``ns`` instead of ``H``, ``T``, ``S``, ``L``, ``U``, and ``N``, for compatibility with respective deprecations in frequency aliases (:issue:`52536`)
@@ -395,7 +422,7 @@ Other Deprecations
 - Deprecated :meth:`.DataFrameGroupBy.fillna` and :meth:`.SeriesGroupBy.fillna`; use :meth:`.DataFrameGroupBy.ffill`, :meth:`.DataFrameGroupBy.bfill` for forward and backward filling or :meth:`.DataFrame.fillna` to fill with a single value (or the Series equivalents) (:issue:`55718`)
 - Deprecated :meth:`Index.format`, use ``index.astype(str)`` or ``index.map(formatter)`` instead (:issue:`55413`)
 - Deprecated :meth:`Series.ravel`, the underlying array is already 1D, so ravel is not necessary (:issue:`52511`)
-- Deprecated :meth:`Series.view`, use ``astype`` instead to change the dtype (:issue:`20251`)
+- Deprecated :meth:`Series.view`, use :meth:`Series.astype` instead to change the dtype (:issue:`20251`)
 - Deprecated ``core.internals`` members ``Block``, ``ExtensionBlock``, and ``DatetimeTZBlock``, use public APIs instead (:issue:`55139`)
 - Deprecated ``year``, ``month``, ``quarter``, ``day``, ``hour``, ``minute``, and ``second`` keywords in the :class:`PeriodIndex` constructor, use :meth:`PeriodIndex.from_fields` instead (:issue:`55960`)
 - Deprecated allowing non-integer ``periods`` argument in :func:`date_range`, :func:`timedelta_range`, :func:`period_range`, and :func:`interval_range` (:issue:`56036`)
@@ -414,11 +441,10 @@ Other Deprecations
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_string` except ``buf``. (:issue:`54229`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_xml` except ``path_or_buffer``. (:issue:`54229`)
 - Deprecated allowing passing :class:`BlockManager` objects to :class:`DataFrame` or :class:`SingleBlockManager` objects to :class:`Series` (:issue:`52419`)
-- Deprecated automatic downcasting of object-dtype results in :meth:`Series.replace` and :meth:`DataFrame.replace`, explicitly call ``result = result.infer_objects(copy=False)`` instead. To opt in to the future version, use ``pd.set_option("future.no_silent_downcasting", True)`` (:issue:`54710`)
 - Deprecated downcasting behavior in :meth:`Series.where`, :meth:`DataFrame.where`, :meth:`Series.mask`, :meth:`DataFrame.mask`, :meth:`Series.clip`, :meth:`DataFrame.clip`; in a future version these will not infer object-dtype columns to non-object dtype, or all-round floats to integer dtype. Call ``result.infer_objects(copy=False)`` on the result for object inference, or explicitly cast floats to ints. To opt in to the future version, use ``pd.set_option("future.no_silent_downcasting", True)`` (:issue:`53656`)
-- Deprecated including the groups in computations when using :meth:`DataFrameGroupBy.apply` and :meth:`DataFrameGroupBy.resample`; pass ``include_groups=False`` to exclude the groups (:issue:`7155`)
+- Deprecated including the groups in computations when using :meth:`.DataFrameGroupBy.apply` and :meth:`.DataFrameGroupBy.resample`; pass ``include_groups=False`` to exclude the groups (:issue:`7155`)
 - Deprecated indexing an :class:`Index`  with a boolean indexer of length zero (:issue:`55820`)
-- Deprecated not passing a tuple to :class:`DataFrameGroupBy.get_group` or :class:`SeriesGroupBy.get_group` when grouping by a length-1 list-like (:issue:`25971`)
+- Deprecated not passing a tuple to :class:`.DataFrameGroupBy.get_group` or :class:`.SeriesGroupBy.get_group` when grouping by a length-1 list-like (:issue:`25971`)
 - Deprecated string ``AS`` denoting frequency in :class:`YearBegin` and strings ``AS-DEC``, ``AS-JAN``, etc. denoting annual frequencies with various fiscal year starts (:issue:`54275`)
 - Deprecated string ``A`` denoting frequency in :class:`YearEnd` and strings ``A-DEC``, ``A-JAN``, etc. denoting annual frequencies with various fiscal year ends (:issue:`54275`)
 - Deprecated string ``BAS`` denoting frequency in :class:`BYearBegin` and strings ``BAS-DEC``, ``BAS-JAN``, etc. denoting annual frequencies with various fiscal year starts (:issue:`54275`)
@@ -439,7 +465,6 @@ Other Deprecations
 - Deprecated the extension test classes ``BaseNoReduceTests``, ``BaseBooleanReduceTests``, and ``BaseNumericReduceTests``, use ``BaseReduceTests`` instead (:issue:`54663`)
 - Deprecated the option ``mode.data_manager`` and the ``ArrayManager``; only the ``BlockManager`` will be available in future versions (:issue:`55043`)
 - Deprecated the previous implementation of :class:`DataFrame.stack`; specify ``future_stack=True`` to adopt the future version (:issue:`53515`)
-- Deprecating downcasting the results of :meth:`DataFrame.fillna`, :meth:`Series.fillna`, :meth:`DataFrame.ffill`, :meth:`Series.ffill`, :meth:`DataFrame.bfill`, :meth:`Series.bfill` in object-dtype cases. To opt in to the future version, use ``pd.set_option("future.no_silent_downcasting", True)`` (:issue:`54261`)
 -
 
 .. ---------------------------------------------------------------------------
@@ -452,19 +477,19 @@ Performance improvements
 - Performance improvement in :func:`get_dummies` (:issue:`56089`)
 - Performance improvement in :func:`merge_asof` when ``by`` is not ``None`` (:issue:`55580`, :issue:`55678`)
 - Performance improvement in :func:`read_stata` for files with many variables (:issue:`55515`)
-- Performance improvement in :func:`to_dict` on converting DataFrame to dictionary (:issue:`50990`)
 - Performance improvement in :meth:`DataFrame.groupby` when aggregating pyarrow timestamp and duration dtypes (:issue:`55031`)
 - Performance improvement in :meth:`DataFrame.loc` and :meth:`Series.loc` when indexing with a :class:`MultiIndex` (:issue:`56062`)
 - Performance improvement in :meth:`DataFrame.sort_index` and :meth:`Series.sort_index` when indexed by a :class:`MultiIndex` (:issue:`54835`)
+- Performance improvement in :meth:`DataFrame.to_dict` on converting DataFrame to dictionary (:issue:`50990`)
 - Performance improvement in :meth:`Index.difference` (:issue:`55108`)
 - Performance improvement in :meth:`Index.sort_values` when index is already sorted (:issue:`56128`)
 - Performance improvement in :meth:`MultiIndex.get_indexer` when ``method`` is not ``None`` (:issue:`55839`)
 - Performance improvement in :meth:`Series.duplicated` for pyarrow dtypes (:issue:`55255`)
 - Performance improvement in :meth:`Series.str.get_dummies` when dtype is ``"string[pyarrow]"`` or ``"string[pyarrow_numpy]"`` (:issue:`56110`)
 - Performance improvement in :meth:`Series.str` methods (:issue:`55736`)
 - Performance improvement in :meth:`Series.value_counts` and :meth:`Series.mode` for masked dtypes (:issue:`54984`, :issue:`55340`)
-- Performance improvement in :meth:`DataFrameGroupBy.nunique` and :meth:`SeriesGroupBy.nunique` (:issue:`55972`)
-- Performance improvement in :meth:`SeriesGroupBy.idxmax`, :meth:`SeriesGroupBy.idxmin`, :meth:`DataFrameGroupBy.idxmax`, :meth:`DataFrameGroupBy.idxmin` (:issue:`54234`)
+- Performance improvement in :meth:`.DataFrameGroupBy.nunique` and :meth:`.SeriesGroupBy.nunique` (:issue:`55972`)
+- Performance improvement in :meth:`.SeriesGroupBy.idxmax`, :meth:`.SeriesGroupBy.idxmin`, :meth:`.DataFrameGroupBy.idxmax`, :meth:`.DataFrameGroupBy.idxmin` (:issue:`54234`)
 - Performance improvement when indexing into a non-unique index (:issue:`55816`)
 - Performance improvement when indexing with more than 4 keys (:issue:`54550`)
 - Performance improvement when localizing time to UTC (:issue:`55241`)
@@ -506,7 +531,7 @@ Datetimelike
 - Bug in creating a :class:`Index`, :class:`Series`, or :class:`DataFrame` with a non-nanosecond ``datetime64`` dtype and inputs that would be out of bounds for a ``datetime64[ns]`` incorrectly raising ``OutOfBoundsDatetime`` (:issue:`55756`)
 - Bug in parsing datetime strings with nanosecond resolution with non-ISO8601 formats incorrectly truncating sub-microsecond components (:issue:`56051`)
 - Bug in parsing datetime strings with sub-second resolution and trailing zeros incorrectly inferring second or millisecond resolution (:issue:`55737`)
-- Bug in the results of :func:`pd.to_datetime` with an floating-dtype argument with ``unit`` not matching the pointwise results of :class:`Timestamp` (:issue:`56037`)
+- Bug in the results of :func:`to_datetime` with an floating-dtype argument with ``unit`` not matching the pointwise results of :class:`Timestamp` (:issue:`56037`)
 -
 
 Timedelta
@@ -528,7 +553,7 @@ Numeric
 
 Conversion
 ^^^^^^^^^^
-- Bug in :func:`astype` when called with ``str`` on unpickled array - the array might change in-place (:issue:`54654`)
+- Bug in :meth:`DataFrame.astype` when called with ``str`` on unpickled array - the array might change in-place (:issue:`54654`)
 - Bug in :meth:`Series.convert_dtypes` not converting all NA column to ``null[pyarrow]`` (:issue:`55346`)
 -
 
@@ -570,10 +595,10 @@ I/O
 - Bug in :func:`read_csv` with ``engine="pyarrow"`` where ``usecols`` wasn't working with a csv with no headers (:issue:`54459`)
 - Bug in :func:`read_excel`, with ``engine="xlrd"`` (``xls`` files) erroring when file contains NaNs/Infs (:issue:`54564`)
 - Bug in :func:`read_json` not handling dtype conversion properly if ``infer_string`` is set (:issue:`56195`)
-- Bug in :func:`to_excel`, with ``OdsWriter`` (``ods`` files) writing boolean/string value (:issue:`54994`)
+- Bug in :meth:`DataFrame.to_excel`, with ``OdsWriter`` (``ods`` files) writing boolean/string value (:issue:`54994`)
 - Bug in :meth:`DataFrame.to_hdf` and :func:`read_hdf` with ``datetime64`` dtypes with non-nanosecond resolution failing to round-trip correctly (:issue:`55622`)
-- Bug in :meth:`pandas.read_excel` with ``engine="odf"`` (``ods`` files) when string contains annotation (:issue:`55200`)
-- Bug in :meth:`pandas.read_excel` with an ODS file without cached formatted cell for float values (:issue:`55219`)
+- Bug in :meth:`~pandas.read_excel` with ``engine="odf"`` (``ods`` files) when string contains annotation (:issue:`55200`)
+- Bug in :meth:`~pandas.read_excel` with an ODS file without cached formatted cell for float values (:issue:`55219`)
 - Bug where :meth:`DataFrame.to_json` would raise an ``OverflowError`` instead of a ``TypeError`` with unsupported NumPy types (:issue:`55403`)
 
 Period
@@ -594,24 +619,24 @@ Groupby/resample/rolling
 - Bug in :class:`.Rolling` where duplicate datetimelike indexes are treated as consecutive rather than equal with ``closed='left'`` and ``closed='neither'`` (:issue:`20712`)
 - Bug in :meth:`.DataFrameGroupBy.idxmin`, :meth:`.DataFrameGroupBy.idxmax`, :meth:`.SeriesGroupBy.idxmin`, and :meth:`.SeriesGroupBy.idxmax` would not retain :class:`.Categorical` dtype when the index was a :class:`.CategoricalIndex` that contained NA values (:issue:`54234`)
 - Bug in :meth:`.DataFrameGroupBy.transform` and :meth:`.SeriesGroupBy.transform` when ``observed=False`` and ``f="idxmin"`` or ``f="idxmax"`` would incorrectly raise on unobserved categories (:issue:`54234`)
+- Bug in :meth:`.DataFrameGroupBy.value_counts` and :meth:`.SeriesGroupBy.value_count` could result in incorrect sorting if the columns of the DataFrame or name of the Series are integers (:issue:`55951`)
+- Bug in :meth:`.DataFrameGroupBy.value_counts` and :meth:`.SeriesGroupBy.value_count` would not respect ``sort=False`` in :meth:`DataFrame.groupby` and :meth:`Series.groupby` (:issue:`55951`)
+- Bug in :meth:`.DataFrameGroupBy.value_counts` and :meth:`.SeriesGroupBy.value_count` would sort by proportions rather than frequencies when ``sort=True`` and ``normalize=True`` (:issue:`55951`)
 - Bug in :meth:`DataFrame.asfreq` and :meth:`Series.asfreq` with a :class:`DatetimeIndex` with non-nanosecond resolution incorrectly converting to nanosecond resolution (:issue:`55958`)
 - Bug in :meth:`DataFrame.ewm` when passed ``times`` with non-nanosecond ``datetime64`` or :class:`DatetimeTZDtype` dtype (:issue:`56262`)
 - Bug in :meth:`DataFrame.resample` not respecting ``closed`` and ``label`` arguments for :class:`~pandas.tseries.offsets.BusinessDay` (:issue:`55282`)
 - Bug in :meth:`DataFrame.resample` where bin edges were not correct for :class:`~pandas.tseries.offsets.BusinessDay` (:issue:`55281`)
 - Bug in :meth:`DataFrame.resample` where bin edges were not correct for :class:`~pandas.tseries.offsets.MonthBegin` (:issue:`55271`)
-- Bug in :meth:`DataFrameGroupBy.value_counts` and :meth:`SeriesGroupBy.value_count` could result in incorrect sorting if the columns of the DataFrame or name of the Series are integers (:issue:`55951`)
-- Bug in :meth:`DataFrameGroupBy.value_counts` and :meth:`SeriesGroupBy.value_count` would not respect ``sort=False`` in :meth:`DataFrame.groupby` and :meth:`Series.groupby` (:issue:`55951`)
-- Bug in :meth:`DataFrameGroupBy.value_counts` and :meth:`SeriesGroupBy.value_count` would sort by proportions rather than frequencies when ``sort=True`` and ``normalize=True`` (:issue:`55951`)
 -
 
 Reshaping
 ^^^^^^^^^
 - Bug in :func:`concat` ignoring ``sort`` parameter when passed :class:`DatetimeIndex` indexes (:issue:`54769`)
 - Bug in :func:`merge_asof` raising ``TypeError`` when ``by`` dtype is not ``object``, ``int64``, or ``uint64`` (:issue:`22794`)
 - Bug in :func:`merge` returning columns in incorrect order when left and/or right is empty (:issue:`51929`)
-- Bug in :meth:`pandas.DataFrame.melt` where an exception was raised if ``var_name`` was not a string (:issue:`55948`)
-- Bug in :meth:`pandas.DataFrame.melt` where it would not preserve the datetime (:issue:`55254`)
-- Bug in :meth:`pandas.DataFrame.pivot_table` where the row margin is incorrect when the columns have numeric names (:issue:`26568`)
+- Bug in :meth:`DataFrame.melt` where an exception was raised if ``var_name`` was not a string (:issue:`55948`)
+- Bug in :meth:`DataFrame.melt` where it would not preserve the datetime (:issue:`55254`)
+- Bug in :meth:`DataFrame.pivot_table` where the row margin is incorrect when the columns have numeric names (:issue:`26568`)
 
 Sparse
 ^^^^^^
@@ -635,7 +660,7 @@ Other
 - Bug in :func:`cut` incorrectly allowing cutting of timezone-aware datetimes with timezone-naive bins (:issue:`54964`)
 - Bug in :func:`infer_freq` and :meth:`DatetimeIndex.inferred_freq` with weekly frequencies and non-nanosecond resolutions (:issue:`55609`)
 - Bug in :meth:`DataFrame.apply` where passing ``raw=True`` ignored ``args`` passed to the applied function (:issue:`55009`)
-- Bug in :meth:`Dataframe.from_dict` which would always sort the rows of the created :class:`DataFrame`.  (:issue:`55683`)
+- Bug in :meth:`DataFrame.from_dict` which would always sort the rows of the created :class:`DataFrame`.  (:issue:`55683`)
 - Bug in rendering ``inf`` values inside a a :class:`DataFrame` with the ``use_inf_as_na`` option enabled (:issue:`55483`)
 - Bug in rendering a :class:`Series` with a :class:`MultiIndex` when one of the index level's names is 0 not having that name displayed (:issue:`55415`)
 - Bug in the error message when assigning an empty dataframe to a column (:issue:`55956`)