feat(config): Support --config in pyproject.toml

.gitignore

@@ -1,11 +1,8 @@
 .venv
-.coverage
-.coverage.*
 _build
 .DS_Store
 .vscode
 docs/_static/pypi.svg
-.tox
 __pycache__
 
 # Packaging artifacts
@@ -21,6 +18,13 @@ src/_black_version.py
 
 .dmypy.json
 *.swp
-.hypothesis/
 venv/
 .ipynb_checkpoints/
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.coverage
+.coverage.*
+.hypothesis/
+.pytest_cache/

CHANGES.md

@@ -58,6 +58,7 @@ and the first release covered by our new stability policy.
 - Enable Python 3.10+ by default, without any extra need to specify
   `--target-version=py310`. (#2758)
 - Make passing `SRC` or `--code` mandatory and mutually exclusive (#2804)
+- Allow specifying `config` in config files (#2525)
 
 ### Output
 

docs/usage_and_configuration/the_basics.md

@@ -200,6 +200,40 @@ project.
 "No". _Black_ is all about sensible defaults. Applying those defaults will have your
 code in compliance with many other _Black_ formatted projects.
 
+### Linked Configuration feature
+
+You can use the `config = ` field to include configuration options from another
+configuration file. Values set in the original configuration file have precedence over
+those in the included file.
+
+Suppose `pyproject.toml` contains:
+
+```{code-block} toml
+---
+lineno-start: 1
+emphasize-lines: 2,3
+---
+[tools.black]
+config = "linked_config.toml"
+color = true
+```
+
+And `linked_config.toml` contains:
+
+```{code-block} toml
+---
+lineno-start: 1
+emphasize-lines: 2
+---
+[tools.black]
+color = false
+line-length = 88
+target-version = ['py36', 'py37', 'py38']
+```
+
+The resulting value for `color` would be `true` as specified in the first config
+(`pyproject.toml`).
+
 ### What on Earth is a `pyproject.toml` file?
 
 [PEP 518](https://www.python.org/dev/peps/pep-0518/) defines `pyproject.toml` as a

src/black/__init__.py

@@ -127,28 +127,44 @@ def read_pyproject_toml(
 
     if not config:
         return None
+
+    inner_config = config.get("config") or (
+        ctx.default_map.get("config") if ctx.default_map else None
+    )
+    if inner_config:
+        inner_config_path = (Path(value).parent / inner_config).resolve()
+
+        try:
+            read_pyproject_toml(ctx, param, str(inner_config_path))
+        except RecursionError as e:
+            raise click.FileError(
+                filename=value, hint=f"Error reading configuration file: {e}"
+            ) from None
+
+        del config["config"]
+
+        if ctx.default_map:
+            ctx.default_map.update(config)
+            config = ctx.default_map.copy()
     else:
-        # Sanitize the values to be Click friendly. For more information please see:
-        # https://github.com/psf/black/issues/1458
-        # https://github.com/pallets/click/issues/1567
-        config = {
-            k: str(v) if not isinstance(v, (list, dict)) else v
-            for k, v in config.items()
-        }
+        if ctx.default_map:
+            config.update(ctx.default_map)
+
+    # Sanitize the values to be Click friendly. For more information please see:
+    # https://github.com/psf/black/issues/1458
+    # https://github.com/pallets/click/issues/1567
+    default_map: Dict[str, Any] = {
+        k: str(v) if not isinstance(v, (list, dict)) else v for k, v in config.items()
+    }
 
-    target_version = config.get("target_version")
+    target_version = default_map.get("target_version")
     if target_version is not None and not isinstance(target_version, list):
         raise click.BadOptionUsage(
             "target-version", "Config key target-version must be a list"
         )
 
-    default_map: Dict[str, Any] = {}
-    if ctx.default_map:
-        default_map.update(ctx.default_map)
-    default_map.update(config)
-
     ctx.default_map = default_map
-    return value
+    return str(value)
 
 
 def target_version_option_callback(

tests/data/toml_configs/_black_config.toml

@@ -0,0 +1,9 @@
+[tool.black]
+verbose = 1
+--check = "no"
+diff = "y"
+color = true
+line-length = 88
+target-version = ["py36", "py37", "py38"]
+exclude='\.pyi?$'
+include='\.py?$'

tests/data/toml_configs/invalid_test.toml

@@ -0,0 +1,2 @@
+[tool.black]
+config = "tests/bazqux.toml"

tests/data/toml_configs/recursion_1.toml

@@ -0,0 +1,2 @@
+[tool.black]
+config = "recursion_2.toml"

tests/data/toml_configs/recursion_2.toml

@@ -0,0 +1,2 @@
+[tool.black]
+config = "recursion_1.toml"

tests/data/toml_configs/test_replace.toml

@@ -0,0 +1,4 @@
+[tool.black]
+config = "_black_config.toml"
+verbose = 0
+color = false

tests/test_black.py

@@ -53,6 +53,7 @@
     PROJECT_ROOT,
     PY36_VERSIONS,
     THIS_DIR,
+    TOML_CONFIG_DIR,
     BlackBaseTestCase,
     assert_format,
     change_directory,
@@ -123,7 +124,7 @@ def invokeBlack(
 ) -> None:
     runner = BlackRunner()
     if ignore_config:
-        args = ["--verbose", "--config", str(THIS_DIR / "empty.toml"), *args]
+        args = ["--verbose", "--config", str(TOML_CONFIG_DIR / "empty.toml"), *args]
     result = runner.invoke(black.main, args, catch_exceptions=False)
     assert result.stdout_bytes is not None
     assert result.stderr_bytes is not None
@@ -175,7 +176,7 @@ def test_piping_diff(self) -> None:
         )
         source, _ = read_data("expression.py")
         expected, _ = read_data("expression.diff")
-        config = THIS_DIR / "data" / "empty_pyproject.toml"
+        config = TOML_CONFIG_DIR / "empty_pyproject.toml"
         args = [
             "-",
             "--fast",
@@ -193,7 +194,7 @@ def test_piping_diff(self) -> None:
 
     def test_piping_diff_with_color(self) -> None:
         source, _ = read_data("expression.py")
-        config = THIS_DIR / "data" / "empty_pyproject.toml"
+        config = TOML_CONFIG_DIR / "empty_pyproject.toml"
         args = [
             "-",
             "--fast",
@@ -252,7 +253,7 @@ def test_expression_ff(self) -> None:
 
     def test_expression_diff(self) -> None:
         source, _ = read_data("expression.py")
-        config = THIS_DIR / "data" / "empty_pyproject.toml"
+        config = TOML_CONFIG_DIR / "empty_pyproject.toml"
         expected, _ = read_data("expression.diff")
         tmp_file = Path(black.dump_to_file(source))
         diff_header = re.compile(
@@ -279,7 +280,7 @@ def test_expression_diff(self) -> None:
 
     def test_expression_diff_with_color(self) -> None:
         source, _ = read_data("expression.py")
-        config = THIS_DIR / "data" / "empty_pyproject.toml"
+        config = TOML_CONFIG_DIR / "empty_pyproject.toml"
         expected, _ = read_data("expression.diff")
         tmp_file = Path(black.dump_to_file(source))
         try:
@@ -1283,7 +1284,7 @@ def test_invalid_config_return_code(self) -> None:
             tmp_file.unlink()
 
     def test_parse_pyproject_toml(self) -> None:
-        test_toml_file = THIS_DIR / "test.toml"
+        test_toml_file = TOML_CONFIG_DIR / "test.toml"
         config = black.parse_pyproject_toml(str(test_toml_file))
         self.assertEqual(config["verbose"], 1)
         self.assertEqual(config["check"], "no")
@@ -1296,7 +1297,7 @@ def test_parse_pyproject_toml(self) -> None:
         self.assertEqual(config["include"], r"\.py?$")
 
     def test_read_pyproject_toml(self) -> None:
-        test_toml_file = THIS_DIR / "test.toml"
+        test_toml_file = TOML_CONFIG_DIR / "test.toml"
         fake_ctx = FakeContext()
         black.read_pyproject_toml(fake_ctx, FakeParameter(), str(test_toml_file))
         config = fake_ctx.default_map
@@ -1309,6 +1310,34 @@ def test_read_pyproject_toml(self) -> None:
         self.assertEqual(config["exclude"], r"\.pyi?$")
         self.assertEqual(config["include"], r"\.py?$")
 
+    def test_black_replace_config(self) -> None:
+        test_toml_file = TOML_CONFIG_DIR / "test_replace.toml"
+        fake_ctx = FakeContext()
+        black.read_pyproject_toml(fake_ctx, FakeParameter(), str(test_toml_file))
+        config = fake_ctx.default_map
+        # `0` in `test_replace.toml` and `1` in `_black_config.toml`.
+        # Should be `0` as the root config is on a higher level than linked configs
+        self.assertEqual(config["verbose"], "0")
+        self.assertEqual(config["check"], "no")
+        self.assertEqual(config["diff"], "y")
+        self.assertEqual(config["color"], "False")
+        self.assertEqual(config["line_length"], "88")
+        self.assertEqual(config["target_version"], ["py36", "py37", "py38"])
+        self.assertEqual(config["exclude"], r"\.pyi?$")
+        self.assertEqual(config["include"], r"\.py?$")
+
+    def test_invalid_black_config(self) -> None:
+        test_toml_file = TOML_CONFIG_DIR / "invalid_test.toml"
+        fake_ctx = FakeContext()
+        with self.assertRaises(click.exceptions.FileError):
+            black.read_pyproject_toml(fake_ctx, FakeParameter(), str(test_toml_file))
+
+    def test_recursion_black_config(self) -> None:
+        test_toml_file = TOML_CONFIG_DIR / "recursion_1.toml"
+        fake_ctx = FakeContext()
+        with self.assertRaises(click.exceptions.FileError):
+            black.read_pyproject_toml(fake_ctx, FakeParameter(), str(test_toml_file))
+
     @pytest.mark.incompatible_with_mypyc
     def test_find_project_root(self) -> None:
         with TemporaryDirectory() as workspace:

tests/util.py

@@ -13,6 +13,7 @@
 
 THIS_DIR = Path(__file__).parent
 DATA_DIR = THIS_DIR / "data"
+TOML_CONFIG_DIR = DATA_DIR / "toml_configs"
 PROJECT_ROOT = THIS_DIR.parent
 EMPTY_LINE = "# EMPTY LINE WITH WHITESPACE" + " (this comment will be removed)"
 DETERMINISTIC_HEADER = "[Deterministic header]"