From 97bb360f2b7f23350fd10dcde6c3751121544445 Mon Sep 17 00:00:00 2001
From: Elliott Sales de Andrade <quantum.analyst@gmail.com>
Date: Fri, 4 Sep 2026 14:57:53 -0400
Subject: [PATCH] Reduce API surface of internal dataclasses

In almost all cases, these are not modified, so they can be marked
`frozen` and with `slots` to make them immutable. We can also drop the
`__eq__` method for _really_ internal things that are just data.
---
 galleries/examples/widgets/menu.py |  2 +-
 lib/matplotlib/dviread.py          |  2 +-
 lib/matplotlib/dviread.pyi         |  2 +-
 lib/matplotlib/font_manager.py     |  4 ++--
 lib/matplotlib/font_manager.pyi    |  2 +-
 lib/matplotlib/rcsetup.py          |  6 +++---
 lib/mpl_toolkits/mplot3d/axis3d.py | 10 +++++-----
 7 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/galleries/examples/widgets/menu.py b/galleries/examples/widgets/menu.py
index 0591b40a29ef..acf12f3b1765 100644
--- a/galleries/examples/widgets/menu.py
+++ b/galleries/examples/widgets/menu.py
@@ -15,7 +15,7 @@
 from matplotlib.typing import ColorType
 
 
-@dataclass
+@dataclass(frozen=True, kw_only=True, slots=True)
 class ItemProperties:
     fontsize: float = 14
     labelcolor: ColorType = 'black'
diff --git a/lib/matplotlib/dviread.py b/lib/matplotlib/dviread.py
index 979744d1ef5c..521f75ed7eab 100644
--- a/lib/matplotlib/dviread.py
+++ b/lib/matplotlib/dviread.py
@@ -953,7 +953,7 @@ def _mul1220(num1, num2):
     return (num1*num2) >> 20
 
 
-@dataclasses.dataclass(frozen=True, kw_only=True)
+@dataclasses.dataclass(frozen=True, kw_only=True, slots=True)
 class TexMetrics:
     """
     Metrics of a glyph, with TeX semantics.
diff --git a/lib/matplotlib/dviread.pyi b/lib/matplotlib/dviread.pyi
index b1039fb45b41..334c43f3f52b 100644
--- a/lib/matplotlib/dviread.pyi
+++ b/lib/matplotlib/dviread.pyi
@@ -89,7 +89,7 @@ class Vf(Dvi):
     def __init__(self, filename: str | os.PathLike) -> None: ...
     def __getitem__(self, code: int) -> Page: ...
 
-@dataclasses.dataclass(frozen=True, kw_only=True)
+@dataclasses.dataclass(frozen=True, kw_only=True, slots=True)
 class TexMetrics:
     tex_width: int
     tex_height: int
diff --git a/lib/matplotlib/font_manager.py b/lib/matplotlib/font_manager.py
index acae3cfd15ea..515fd8bd3856 100644
--- a/lib/matplotlib/font_manager.py
+++ b/lib/matplotlib/font_manager.py
@@ -386,7 +386,7 @@ def __repr__(self):
         return f'FontPath{self._as_tuple()}'
 
 
-@dataclasses.dataclass(frozen=True)
+@dataclasses.dataclass(frozen=True, slots=True)
 class FontEntry:
     """
     A class for storing Font properties.
@@ -1076,7 +1076,7 @@ def default(self, o):
         if isinstance(o, FontManager):
             return dict(o.__dict__, __class__='FontManager')
         elif isinstance(o, FontEntry):
-            d = dict(o.__dict__, __class__='FontEntry')
+            d = dict(dataclasses.asdict(o), __class__='FontEntry')
             try:
                 # Cache paths of fonts shipped with Matplotlib relative to the
                 # Matplotlib data path, which helps in the presence of venvs.
diff --git a/lib/matplotlib/font_manager.pyi b/lib/matplotlib/font_manager.pyi
index 2e9b2fcf99f0..b58d0a56e4c0 100644
--- a/lib/matplotlib/font_manager.pyi
+++ b/lib/matplotlib/font_manager.pyi
@@ -46,7 +46,7 @@ class FontPath(str):
     def __hash__(self) -> int: ...
     def __repr__(self) -> str: ...
 
-@dataclass
+@dataclass(frozen=True, slots=True)
 class FontEntry:
     fname: str = ...
     index: int = ...
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
index a0323bd6fd01..8c0b304c9bc0 100644
--- a/lib/matplotlib/rcsetup.py
+++ b/lib/matplotlib/rcsetup.py
@@ -1519,7 +1519,7 @@ def _convert_validator_spec(key, conv):
 type _MarkerType = int | str
 
 
-@dataclass
+@dataclass(eq=False, frozen=True, slots=True)
 class _Param:
     name: str
     default: Any
@@ -1535,13 +1535,13 @@ class _Param:
     description: str | None = None
 
 
-@dataclass
+@dataclass(eq=False, frozen=True, slots=True)
 class _Section:
     title: str
     description: str | None = None
 
 
-@dataclass
+@dataclass(eq=False, frozen=True, slots=True)
 class _Subsection:
     title: str
     description: str | None = None
diff --git a/lib/mpl_toolkits/mplot3d/axis3d.py b/lib/mpl_toolkits/mplot3d/axis3d.py
index fc62b045e367..362f7fe46bfc 100644
--- a/lib/mpl_toolkits/mplot3d/axis3d.py
+++ b/lib/mpl_toolkits/mplot3d/axis3d.py
@@ -36,7 +36,7 @@ def _tick_update_position(tick, tickxs, tickys, labelpos):
     tick.gridline.set_data([0], [0])
 
 
-@dataclass
+@dataclass(eq=False, frozen=True, slots=True)
 class _UpdatedArtists:
     """
     Class to supply artists that have been updated ready to draw.
@@ -44,10 +44,10 @@ class _UpdatedArtists:
     We track the types of artists individually, because they need
     different handling in the tightbox calculation.
     """
-    line: mlines.Line2D = None
-    ticks: list = None
-    offset_text: mtext.Text = None
-    label: mtext.Text = None
+    line: mlines.Line2D | None = None
+    ticks: list | None = None
+    offset_text: mtext.Text | None = None
+    label: mtext.Text | None = None
 
     def __iter__(self):
         """Yield all updated artists in the correct order for drawing"""