Add the -t/--target-version command line option

pyproject.toml

@@ -4,6 +4,7 @@ requires = ["setuptools", "wheel"]  # PEP 508 specifications.
 
 [tool.black]
 skip-string-normalization = false
+target-version = ["py311"]
 
 [tool.isort]
 profile = "black"

src/darker/__main__.py

@@ -387,6 +387,8 @@ def main(  # pylint: disable=too-many-locals,too-many-branches,too-many-statemen
         black_config["config"] = args.config
     if args.line_length:
         black_config["line_length"] = args.line_length
+    if args.target_version:
+        black_config["target_version"] = {args.target_version}
     if args.skip_string_normalization is not None:
         black_config["skip_string_normalization"] = args.skip_string_normalization
     if args.skip_magic_trailing_comma is not None:

src/darker/black_diff.py

@@ -36,7 +36,7 @@
 import logging
 import sys
 from pathlib import Path
-from typing import Collection, Optional, Pattern, Set, Tuple
+from typing import Collection, Optional, Pattern, Set, Tuple, Union
 
 # `FileMode as Mode` required to satisfy mypy==0.782. Strange.
 from black import FileMode as Mode
@@ -54,6 +54,7 @@
 from black.files import gen_python_files
 from black.report import Report
 
+from darker.config import ConfigurationError
 from darker.utils import TextDocument
 
 if sys.version_info >= (3, 8):
@@ -77,7 +78,7 @@ class BlackConfig(TypedDict, total=False):
     exclude: Pattern[str]
     extend_exclude: Pattern[str]
     force_exclude: Pattern[str]
-    target_version: str
+    target_version: Union[str, Set[str]]
     line_length: int
     skip_string_normalization: bool
     skip_magic_trailing_comma: bool
@@ -189,10 +190,15 @@ def run_black(src_contents: TextDocument, black_config: BlackConfig) -> TextDocu
     if "line_length" in black_config:
         mode["line_length"] = black_config["line_length"]
     if "target_version" in black_config:
-        ver_str = black_config["target_version"]
-        ver = next((v for v in TargetVersion if v.name.lower() == ver_str), None)
-        if ver:
-            mode["target_versions"] = {ver}
+        if isinstance(black_config["target_version"], set):
+            target_versions_in = black_config["target_version"]
+        else:
+            target_versions_in = {black_config["target_version"]}
+        all_target_versions = {tgt_v.name.lower(): tgt_v for tgt_v in TargetVersion}
+        bad_target_versions = target_versions_in - set(all_target_versions)
+        if bad_target_versions:
+            raise ConfigurationError(f"Invalid target version(s) {bad_target_versions}")
+        mode["target_versions"] = {all_target_versions[n] for n in target_versions_in}
     if "skip_magic_trailing_comma" in black_config:
         mode["magic_trailing_comma"] = not black_config["skip_magic_trailing_comma"]
     if "skip_string_normalization" in black_config:

src/darker/command_line.py

@@ -85,6 +85,25 @@ def add_arg(help_text: Optional[str], *name_or_flags: str, **kwargs: Any) -> Non
         dest="line_length",
         metavar="LENGTH",
     )
+    add_arg(
+        hlp.TARGET_VERSION,
+        "-t",
+        "--target-version",
+        type=str,
+        dest="target_version",
+        metavar="VERSION",
+        choices=[
+            "py33",
+            "py34",
+            "py35",
+            "py36",
+            "py37",
+            "py38",
+            "py39",
+            "py310",
+            "py311",
+        ],
+    )
     add_arg(hlp.WORKERS, "-W", "--workers", type=int, dest="workers", default=1)
     # A hidden option for printing command lines option in a format suitable for
     # `README.rst`:

src/darker/config.py

@@ -42,6 +42,7 @@ class DarkerConfig(TypedDict, total=False):
     skip_string_normalization: bool
     skip_magic_trailing_comma: bool
     line_length: int
+    target_version: str
     workers: int
 
 

src/darker/help.py

@@ -89,6 +89,10 @@
 
 LINE_LENGTH = "How many characters per line to allow [default: 88]"
 
-TARGET_VERSION = "Python versions that should be supported. [default: py37]"
+TARGET_VERSION = (
+    "[py33|py34|py35|py36|py37|py38|py39|py310|py311]"
+    " Python versions that should be supported by"
+    " Black's output. [default: py311]"
+)
 
 WORKERS = "How many parallel workers to allow, or `0` for one per core [default: 1]"

src/darker/tests/test_command_line.py

@@ -12,6 +12,7 @@
 
 import pytest
 import toml
+from black import TargetVersion
 
 import darker.help
 from darker import black_diff
@@ -395,6 +396,36 @@ def test_parse_command_line_config_location_specified(
         expect_config=("line_length", 99),
         expect_modified=("line_length", 99),
     ),
+    dict(
+        argv=["--target-version", "py37", "."],
+        expect_value=("target_version", "py37"),
+        expect_config=("target_version", "py37"),
+        expect_modified=("target_version", "py37"),
+    ),
+    dict(
+        argv=["--target-version", "py39", "."],
+        expect_value=("target_version", "py39"),
+        expect_config=("target_version", "py39"),
+        expect_modified=("target_version", "py39"),
+    ),
+    dict(
+        argv=["--target-version", "py37", "--target-version", "py39", "."],
+        expect_value=("target_version", "py39"),
+        expect_config=("target_version", "py39"),
+        expect_modified=("target_version", "py39"),
+    ),
+    dict(
+        argv=["--target-version", "py39", "--target-version", "py37", "."],
+        expect_value=("target_version", "py37"),
+        expect_config=("target_version", "py37"),
+        expect_modified=("target_version", "py37"),
+    ),
+    dict(
+        argv=["--target-version", "py39,py37", "."],
+        expect_value=SystemExit,
+        expect_config=None,
+        expect_modified=None,
+    ),
     dict(
         # this is accepted as a path, but would later fail if a file or directory with
         # that funky name doesn't exist
@@ -476,11 +507,19 @@ def test_help_with_isort_package(capsys):
     dict(options=[], expect=call()),
     dict(
         options=["-c", "black.cfg"],
-        expect=call(line_length=81, string_normalization=True),
+        expect=call(
+            line_length=81,
+            string_normalization=True,
+            target_versions={TargetVersion.PY38},
+        ),
     ),
     dict(
         options=["--config", "black.cfg"],
-        expect=call(line_length=81, string_normalization=True),
+        expect=call(
+            line_length=81,
+            string_normalization=True,
+            target_versions={TargetVersion.PY38},
+        ),
     ),
     dict(options=["-S"], expect=call(string_normalization=False)),
     dict(
@@ -490,19 +529,64 @@ def test_help_with_isort_package(capsys):
     dict(options=["--line-length", "90"], expect=call(line_length=90)),
     dict(
         options=["-c", "black.cfg", "-S"],
-        expect=call(line_length=81, string_normalization=False),
+        expect=call(
+            line_length=81,
+            string_normalization=False,
+            target_versions={TargetVersion.PY38},
+        ),
     ),
     dict(
         options=["-c", "black.cfg", "-l", "90"],
-        expect=call(line_length=90, string_normalization=True),
+        expect=call(
+            line_length=90,
+            string_normalization=True,
+            target_versions={TargetVersion.PY38},
+        ),
     ),
     dict(
         options=["-l", "90", "-S"],
         expect=call(line_length=90, string_normalization=False),
     ),
     dict(
         options=["-c", "black.cfg", "-l", "90", "-S"],
-        expect=call(line_length=90, string_normalization=False),
+        expect=call(
+            line_length=90,
+            string_normalization=False,
+            target_versions={TargetVersion.PY38},
+        ),
+    ),
+    dict(options=["-t", "py39"], expect=call(target_versions={TargetVersion.PY39})),
+    dict(
+        options=["--target-version", "py39"],
+        expect=call(target_versions={TargetVersion.PY39}),
+    ),
+    dict(
+        options=["-c", "black.cfg", "-S"],
+        expect=call(
+            line_length=81,
+            string_normalization=False,
+            target_versions={TargetVersion.PY38},
+        ),
+    ),
+    dict(
+        options=["-c", "black.cfg", "-t", "py39"],
+        expect=call(
+            line_length=81,
+            string_normalization=True,
+            target_versions={TargetVersion.PY39},
+        ),
+    ),
+    dict(
+        options=["-t", "py39", "-S"],
+        expect=call(string_normalization=False, target_versions={TargetVersion.PY39}),
+    ),
+    dict(
+        options=["-c", "black.cfg", "-t", "py39", "-S"],
+        expect=call(
+            line_length=81,
+            string_normalization=False,
+            target_versions={TargetVersion.PY39},
+        ),
     ),
 )
 def test_black_options(monkeypatch, tmpdir, git_repo, options, expect):
@@ -515,6 +599,7 @@ def test_black_options(monkeypatch, tmpdir, git_repo, options, expect):
             [tool.black]
             line-length = 81
             skip-string-normalization = false
+            target-version = 'py38'
             """
         )
     )
@@ -572,35 +657,49 @@ def test_black_options(monkeypatch, tmpdir, git_repo, options, expect):
         options=["--no-skip-string-normalization"],
         expect=call(string_normalization=True),
     ),
+    dict(
+        config=[],
+        options=["--skip-magic-trailing-comma"],
+        expect=call(magic_trailing_comma=False),
+    ),
+    dict(
+        config=["skip_magic_trailing_comma = false"],
+        options=[],
+        expect=call(magic_trailing_comma=True),
+    ),
+    dict(
+        config=["skip_magic_trailing_comma = true"],
+        options=[],
+        expect=call(magic_trailing_comma=False),
+    ),
+    dict(
+        config=[],
+        options=["--target-version", "py39"],
+        expect=call(target_versions={TargetVersion.PY39}),
+    ),
+    dict(
+        config=["target-version = 'py39'"],
+        options=[],
+        expect=call(target_versions={TargetVersion.PY39}),
+    ),
+    dict(
+        config=["target_version = ['py39']"],
+        options=[],
+        expect=call(target_versions={TargetVersion.PY39}),
+    ),
+    dict(
+        config=["target-version = 'py38'"],
+        options=["--target-version", "py39"],
+        expect=call(target_versions={TargetVersion.PY39}),
+    ),
+    dict(
+        config=["target-version = ['py38']"],
+        options=["-t", "py39"],
+        expect=call(target_versions={TargetVersion.PY39}),
+    ),
 )
-def test_black_options_skip_string_normalization(git_repo, config, options, expect):
-    """Black string normalization config and cmdline option are combined correctly"""
-    added_files = git_repo.add(
-        {"main.py": "foo", "pyproject.toml": joinlines(["[tool.black]"] + config)},
-        commit="Initial commit",
-    )
-    added_files["main.py"].write_bytes(b"bar")
-    mode_class_mock = Mock(wraps=black_diff.Mode)
-    # Speed up tests by mocking `format_str` to skip running Black
-    format_str = Mock(return_value="bar")
-    with patch.multiple(black_diff, Mode=mode_class_mock, format_str=format_str):
-
-        main(options + [str(path) for path in added_files.values()])
-
-    assert mode_class_mock.call_args_list == [expect]
-
-
-@pytest.mark.parametrize(
-    "config, options, expect",
-    [
-        ([], [], call()),
-        ([], ["--skip-magic-trailing-comma"], call(magic_trailing_comma=False)),
-        (["skip_magic_trailing_comma = false"], [], call(magic_trailing_comma=True)),
-        (["skip_magic_trailing_comma = true"], [], call(magic_trailing_comma=False)),
-    ],
-)
-def test_black_options_skip_magic_trailing_comma(git_repo, config, options, expect):
-    """Black string normalization config and cmdline option are combined correctly"""
+def test_black_config_file_and_options(git_repo, config, options, expect):
+    """Black configuration file and command line options are combined correctly"""
     added_files = git_repo.add(
         {"main.py": "foo", "pyproject.toml": joinlines(["[tool.black]"] + config)},
         commit="Initial commit",
@@ -679,6 +778,16 @@ def test_black_options_skip_magic_trailing_comma(git_repo, config, options, expe
             {},
         ),
     ),
+    dict(
+        options=["--target-version", "py39", "a.py"],
+        expect=(
+            Path("git_root"),
+            {Path("a.py")},
+            Exclusions(black=set(), isort={"**/*"}),
+            RevisionRange("HEAD", ":WORKTREE:"),
+            {"target_version": {"py39"}},
+        ),
+    ),
 )
 def test_options(git_repo, options, expect):
     """The main engine is called with correct parameters based on the command line