API: make construct_array_type non-optional (#41862)

Author: jbrockmendel

doc/source/whatsnew/v1.3.0.rst

@@ -697,6 +697,7 @@ Other API changes
 - Accessing ``_constructor_expanddim`` on a :class:`DataFrame` and ``_constructor_sliced`` on a :class:`Series` now raise an ``AttributeError``. Previously a ``NotImplementedError`` was raised (:issue:`38782`)
 - Added new ``engine`` and ``**engine_kwargs`` parameters to :meth:`DataFrame.to_sql` to support other future "SQL engines". Currently we still only use ``SQLAlchemy`` under the hood, but more engines are planned to be supported such as ``turbodbc`` (:issue:`36893`)
 - Removed redundant ``freq`` from :class:`PeriodIndex` string representation (:issue:`41653`)
+- :meth:`ExtensionDtype.construct_array_type` is now a required method instead of an optional one for :class:`ExtensionDtype` subclasses (:issue:`24860`)
 
 Build
 =====

pandas/core/dtypes/base.py

@@ -48,6 +48,7 @@ class ExtensionDtype:
 
     * type
     * name
+    * construct_array_type
 
     The following attributes and methods influence the behavior of the dtype in
     pandas operations
@@ -56,12 +57,6 @@ class ExtensionDtype:
     * _is_boolean
     * _get_common_dtype
 
-    Optionally one can override construct_array_type for construction
-    with the name of this dtype via the Registry. See
-    :meth:`extensions.register_extension_dtype`.
-
-    * construct_array_type
-
     The `na_value` class attribute can be used to set the default NA value
     for this type. :attr:`numpy.nan` is used by default.
 
@@ -205,7 +200,7 @@ def construct_array_type(cls) -> type_t[ExtensionArray]:
         -------
         type
         """
-        raise NotImplementedError
+        raise AbstractMethodError(cls)
 
     @classmethod
     def construct_from_string(cls, string: str):