From beb8e3f2763d35ed85ae4bb82ef0073dfaaa3a67 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Thu, 19 Feb 2026 22:13:16 +0100
Subject: [PATCH] gh-141510: Document ParameterizedMIMEHeader.params change
 (#145003)

Document also the dataclasses.field() metadata change.
---
 Doc/library/dataclasses.rst                                   | 4 ++++
 Doc/library/email.headerregistry.rst                          | 4 ++++
 .../Library/2026-02-19-16-26-08.gh-issue-141510.4Qxy8_.rst    | 3 +++
 .../Library/2026-02-19-18-02-54.gh-issue-141510.qzvYsO.rst    | 3 +++
 4 files changed, 14 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-02-19-16-26-08.gh-issue-141510.4Qxy8_.rst
 create mode 100644 Misc/NEWS.d/next/Library/2026-02-19-18-02-54.gh-issue-141510.qzvYsO.rst

diff --git a/Doc/library/dataclasses.rst b/Doc/library/dataclasses.rst
index cff36e25822..2864149a08f 100644
--- a/Doc/library/dataclasses.rst
+++ b/Doc/library/dataclasses.rst
@@ -333,6 +333,10 @@ Module contents
    :attr:`!C.t` will be ``20``, and the class attributes :attr:`!C.x` and
    :attr:`!C.y` will not be set.
 
+   .. versionchanged:: next
+      If *metadata* is ``None``, use an empty :class:`frozendict`, instead
+      of a :func:`~types.MappingProxyType` of an empty :class:`dict`.
+
 .. class:: Field
 
    :class:`!Field` objects describe each defined field. These objects
diff --git a/Doc/library/email.headerregistry.rst b/Doc/library/email.headerregistry.rst
index ff8b601fe3d..f4c11821c4b 100644
--- a/Doc/library/email.headerregistry.rst
+++ b/Doc/library/email.headerregistry.rst
@@ -269,6 +269,10 @@ variant, :attr:`~.BaseHeader.max_count` is set to 1.
 
        A dictionary mapping parameter names to parameter values.
 
+       .. versionchanged:: next
+          It is now a :class:`frozendict` instead of a
+          :class:`types.MappingProxyType`.
+
 
 .. class:: ContentTypeHeader
 
diff --git a/Misc/NEWS.d/next/Library/2026-02-19-16-26-08.gh-issue-141510.4Qxy8_.rst b/Misc/NEWS.d/next/Library/2026-02-19-16-26-08.gh-issue-141510.4Qxy8_.rst
new file mode 100644
index 00000000000..cf22e82b841
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-02-19-16-26-08.gh-issue-141510.4Qxy8_.rst
@@ -0,0 +1,3 @@
+``ParameterizedMIMEHeader.params`` of :mod:`email.headerregistry` is now a
+:class:`frozendict` instead of a :class:`types.MappingProxyType`. Patch by
+Victor Stinner.
diff --git a/Misc/NEWS.d/next/Library/2026-02-19-18-02-54.gh-issue-141510.qzvYsO.rst b/Misc/NEWS.d/next/Library/2026-02-19-18-02-54.gh-issue-141510.qzvYsO.rst
new file mode 100644
index 00000000000..ae46ff0cbdd
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-02-19-18-02-54.gh-issue-141510.qzvYsO.rst
@@ -0,0 +1,3 @@
+:func:`dataclasses.field`: if *metadata* is ``None``, use an empty
+:class:`frozendict`, instead of a :func:`~types.MappingProxyType` of an
+empty :class:`dict`. Patch by Victor Stinner.