From 6289be831a2d4fbbee69b4726a0ad6fd978a8b76 Mon Sep 17 00:00:00 2001
From: Ned Batchelder <ned@nedbatchelder.com>
Date: Wed, 6 Mar 2024 20:16:58 -0500
Subject: [PATCH] refactor: use dataclasses, no namedtuple

---
 coverage/parser.py         | 10 ++++++----
 coverage/sysmon.py         |  4 ++--
 lab/benchmark/benchmark.py |  6 +++---
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/coverage/parser.py b/coverage/parser.py
index 5ad534701..959174c36 100644
--- a/coverage/parser.py
+++ b/coverage/parser.py
@@ -13,6 +13,7 @@
 import token
 import tokenize
 
+from dataclasses import dataclass
 from types import CodeType
 from typing import (
     cast, Any, Callable, Dict, Iterable, List, Optional, Protocol, Sequence,
@@ -462,7 +463,8 @@ def _find_statements(self) -> Iterable[TLineNo]:
 # AST analysis
 #
 
-class ArcStart(collections.namedtuple("Arc", "lineno, cause")):
+@dataclass(frozen=True, order=True)
+class ArcStart:
     """The information needed to start an arc.
 
     `lineno` is the line number the arc starts from.
@@ -474,8 +476,8 @@ class ArcStart(collections.namedtuple("Arc", "lineno, cause")):
     to have `lineno` interpolated into it.
 
     """
-    def __new__(cls, lineno: TLineNo, cause: str | None = None) -> ArcStart:
-        return super().__new__(cls, lineno, cause)
+    lineno: TLineNo
+    cause: str = ""
 
 
 class TAddArcFn(Protocol):
@@ -1256,7 +1258,7 @@ def _combine_finally_starts(self, starts: set[ArcStart], exits: set[ArcStart]) -
         """
         causes = []
         for start in sorted(starts):
-            if start.cause is not None:
+            if start.cause:
                 causes.append(start.cause.format(lineno=start.lineno))
         cause = " or ".join(causes)
         exits = {ArcStart(xit.lineno, cause) for xit in exits}
diff --git a/coverage/sysmon.py b/coverage/sysmon.py
index 5e1371a92..65c5b6e77 100644
--- a/coverage/sysmon.py
+++ b/coverage/sysmon.py
@@ -5,7 +5,6 @@
 
 from __future__ import annotations
 
-import dataclasses
 import functools
 import inspect
 import os
@@ -14,6 +13,7 @@
 import threading
 import traceback
 
+from dataclasses import dataclass
 from types import CodeType, FrameType
 from typing import (
     Any,
@@ -151,7 +151,7 @@ def _decorator(meth: AnyCallable) -> AnyCallable:
         return _decorator
 
 
-@dataclasses.dataclass
+@dataclass
 class CodeInfo:
     """The information we want about each code object."""
 
diff --git a/lab/benchmark/benchmark.py b/lab/benchmark/benchmark.py
index d0d6188fd..1184f0b3e 100644
--- a/lab/benchmark/benchmark.py
+++ b/lab/benchmark/benchmark.py
@@ -2,7 +2,6 @@
 
 import collections
 import contextlib
-import dataclasses
 import itertools
 import os
 import random
@@ -13,6 +12,7 @@
 import time
 from pathlib import Path
 
+from dataclasses import dataclass
 from typing import Any, Dict, Iterable, Iterator, List, Optional, Tuple
 
 import tabulate
@@ -480,7 +480,7 @@ def __init__(self, path, slug):
         self.toxenv = None
 
 
-@dataclasses.dataclass
+@dataclass
 class Coverage:
     """A version of coverage.py to use, maybe None."""
 
@@ -537,7 +537,7 @@ def __init__(self, directory, slug="source", tweaks=None, env_vars=None):
         )
 
 
-@dataclasses.dataclass
+@dataclass
 class Env:
     """An environment to run a test suite in."""