From f2102e16f8feccdf1c65474edbf91f8248710ee7 Mon Sep 17 00:00:00 2001
From: Antti Kaihola <13725+akaihola@users.noreply.github.com>
Date: Wed, 20 Mar 2024 21:34:04 +0200
Subject: [PATCH] Add `formatter` command line and config option

The only supported value for now is `black`.

Fixes #562
---
 src/darker/command_line.py            |  7 +++++++
 src/darker/config.py                  |  1 +
 src/darker/tests/test_command_line.py | 24 ++++++++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/src/darker/command_line.py b/src/darker/command_line.py
index 04dd17078..661420405 100644
--- a/src/darker/command_line.py
+++ b/src/darker/command_line.py
@@ -75,6 +75,13 @@ def make_argument_parser(require_src: bool) -> ArgumentParser:
         metavar="VERSION",
         choices=[v.name.lower() for v in TargetVersion],
     )
+    add_arg(
+        "Formatter to use for reformatting code",
+        "--formatter",
+        default="black",
+        choices=["black"],
+        metavar="FORMATTER",
+    )
     return parser
 
 
diff --git a/src/darker/config.py b/src/darker/config.py
index 7beb307d3..e780b217c 100644
--- a/src/darker/config.py
+++ b/src/darker/config.py
@@ -21,6 +21,7 @@ class DarkerConfig(BaseConfig, total=False):
     skip_magic_trailing_comma: bool
     line_length: int
     target_version: str
+    formatter: str
 
 
 class OutputMode:
diff --git a/src/darker/tests/test_command_line.py b/src/darker/tests/test_command_line.py
index 719e5a9fe..65e531057 100644
--- a/src/darker/tests/test_command_line.py
+++ b/src/darker/tests/test_command_line.py
@@ -183,6 +183,30 @@ def get_darker_help_output(capsys):
         expect_config=("target_version", "py37"),
         expect_modified=("target_version", "py37"),
     ),
+    dict(
+        argv=["--formatter", "black", "."],
+        expect_value=("formatter", "black"),
+        expect_config=("formatter", "black"),
+        expect_modified=("formatter", ...),
+    ),
+    dict(
+        argv=["--formatter=black", "."],
+        expect_value=("formatter", "black"),
+        expect_config=("formatter", "black"),
+        expect_modified=("formatter", ...),
+    ),
+    dict(
+        argv=["--formatter", "rustfmt", "."],
+        expect_value=SystemExit,
+        expect_config=None,
+        expect_modified=None,
+    ),
+    dict(
+        argv=["--formatter=rustfmt", "."],
+        expect_value=SystemExit,
+        expect_config=None,
+        expect_modified=None,
+    ),
     dict(
         argv=["--target-version", "py39", "."],
         expect_value=("target_version", "py39"),