Drop support for Python 3.8

.github/workflows/python-package.yml

@@ -88,7 +88,6 @@ jobs:
           - windows-latest
           - macos-latest
         python-version:
-          - '3.8'
           - '3.9'
           - '3.10'
           - '3.11'
@@ -105,7 +104,7 @@ jobs:
             python-version: '3.13-dev'
         include:
           - os: ubuntu-latest
-            python-version: '3.8'
+            python-version: '3.9'
             constraints: '--constraint constraints-oldest.txt'
           - os: ubuntu-latest
             python-version: '3.12'

.github/workflows/pyupgrade.yml

@@ -20,5 +20,5 @@ jobs:
           from pyupgrade._main import main
           from glob import glob
           files = glob('**/*.py', recursive=True)
-          sys.exit(main(files + ['--py38-plus']))
+          sys.exit(main(files + ['--py39-plus']))
           " || ( git diff ; false )

README.rst

@@ -415,7 +415,7 @@ An example ``pyproject.toml`` configuration file:
    line-length = 88                  # Overridden by [tool.darker] above
    skip-magic-trailing-comma = false
    skip-string-normalization = false
-   target-version = ["py38", "py39", "py310", "py311", "py312"]  # Overridden above
+   target-version = ["py39", "py310", "py311", "py312"]  # Overridden above
    exclude = "test_*\.py"
    extend_exclude = "/generated/"
    force_exclude = ".*\.pyi"

pyproject.toml

@@ -6,7 +6,7 @@ requires = ["setuptools", "wheel"]  # PEP 508 specifications.
 # Darker makes Black read its configuration from the file indicated by the `--config`
 # option, so we need to mirror the same configuration here and in `check-darker.toml`.
 skip-string-normalization = false
-target-version = ["py38", "py39", "py310", "py311", "py312"]
+target-version = ["py39", "py310", "py311", "py312"]
 
 [tool.isort]
 # Darker makes isort read its configuration from the file indicated by the `--config`
@@ -37,7 +37,7 @@ src = ["."]
 disable = ["wrong-import-order"]
 
 [tool.ruff]
-target-version = "py38"
+target-version = "py39"
 
 [tool.ruff.lint]
 select = ["ALL"]
@@ -47,10 +47,6 @@ ignore = [
     "D203",  # One blank line required before class docstring
     "D213",  # Multi-line docstring summary should start at the second line
     "D400",  # First line should end with a period (duplicates D415)
-
-    # Remove these when support for Python 3.8 is dropped:
-    "UP006",  # Use `xyz` instead of `Xyz` for type annotation
-    "UP007",  # Use `X | Y` for type annotations
 ]
 
 [tool.ruff.lint.per-file-ignores]

setup.cfg

@@ -10,7 +10,6 @@ description = Apply Black formatting only in regions changed since last commit
 long_description_content_type = text/x-rst
 classifiers =
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
@@ -33,7 +32,7 @@ install_requires =
     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
+python_requires = >=3.9
 
 [options.packages.find]
 where = src

src/darker/concurrency.py

@@ -1,25 +1,10 @@
 """Concurrency helpers for enhancing the performance of Darker"""
 
-import sys
 from concurrent.futures import Executor, Future, ProcessPoolExecutor
-from typing import Any, Callable, Generic, TypeVar, cast
+from typing import Any, Callable, TypeVar
 
 T = TypeVar("T")  # pylint: disable=invalid-name
 
-if sys.version_info < (3, 9):
-
-    class FutureType(Generic[T]):
-        """For Python <3.9 compatibility"""
-
-        def set_exception(self, exc_info: BaseException) -> None:
-            "Dummy method for typing"
-
-        def set_result(self, result: Any) -> None:
-            "Dummy method for typing"
-
-else:
-    FutureType = Future
-
 
 class DummyExecutor(Executor):
     """Dummy synchronous executor to use with ``--workers=1``
@@ -31,7 +16,7 @@ class DummyExecutor(Executor):
     # pylint: disable=arguments-differ,unsubscriptable-object,broad-except
     def submit(  # type: ignore[override]
         self, fn: Callable[..., T], *args: Any, **kwargs: Any
-    ) -> FutureType[T]:
+    ) -> Future[T]:
         """Submits "a callable to be executed with the given arguments.
 
         Executes the callable immediately as ``fn(*args, **kwargs)`` and returns a
@@ -43,7 +28,7 @@ def submit(  # type: ignore[override]
         :return: A `Future` representing the given call
 
         """
-        future = cast(FutureType[T], Future())
+        future: Future[T] = Future()
         try:
             result = fn(*args, **kwargs)
         except BaseException as exc_info:  # noqa: B036