From 1ded5cf06f45431ae319b1957d660ac22b426068 Mon Sep 17 00:00:00 2001
From: Antti Kaihola <13725+akaihola@users.noreply.github.com>
Date: Tue, 24 Sep 2024 08:45:46 +0300
Subject: [PATCH] fix: py38/39 typing compatibility

---
 constraints-oldest.txt |  1 +
 setup.cfg              |  1 +
 src/darker/config.py   | 10 ++++++++--
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/constraints-oldest.txt b/constraints-oldest.txt
index fc3d5b986..70d16afb2 100644
--- a/constraints-oldest.txt
+++ b/constraints-oldest.txt
@@ -20,4 +20,5 @@ ruamel.yaml==0.17.21
 toml==0.10.0
 twine==2.0.0
 types-toml==0.10.4
+typing_extensions==4.0.1
 wheel==0.21.0
diff --git a/setup.cfg b/setup.cfg
index 191d76a96..154679f94 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -31,6 +31,7 @@ install_requires =
     black>=22.3.0
     darkgraylib~=2.0.1
     toml>=0.10.0
+    typing_extensions>=4.0.1
 # NOTE: remember to keep `.github/workflows/python-package.yml` in sync
 #       with the minimum required Python version
 python_requires = >=3.8
diff --git a/src/darker/config.py b/src/darker/config.py
index 561dc38bb..0e143591d 100644
--- a/src/darker/config.py
+++ b/src/darker/config.py
@@ -2,16 +2,22 @@
 
 from __future__ import annotations
 
+import sys
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Union
 
 from darkgraylib.config import BaseConfig, ConfigurationError
 
+if sys.version_info < (3, 10):
+    from typing_extensions import TypeAlias
+else:
+    from typing import TypeAlias
+
 if TYPE_CHECKING:
     from argparse import Namespace
 
-UnvalidatedConfig = dict[str, list[str] | str | bool | int]
+UnvalidatedConfig: TypeAlias = dict[str, Union[list[str], str, bool, int]]
 
 
 REMOVED_CONFIG_OPTIONS = {