Raise exception on invalid toml configuration

CHANGES.md

@@ -62,6 +62,7 @@ release:
 
 <!-- Changes to how Black can be configured -->
 
+- Print warning when toml config contains an invalid key (#4165)
 - Fix symlink handling, properly catch and ignore symlinks that point outside of root
   (#4161)
 - Fix cache mtime logic that resulted in false positive cache hits (#4128)

src/black/__init__.py

@@ -142,6 +142,7 @@ def read_pyproject_toml(
     if not config:
         return None
     else:
+        spellcheck_pyproject_toml_keys(ctx, list(config), value)
         # 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
@@ -181,6 +182,21 @@ def read_pyproject_toml(
     return value
 
 
+def spellcheck_pyproject_toml_keys(
+    ctx: click.Context, config_keys: List[str], config_file_path: str
+) -> None:
+    invalid_keys: List[str] = []
+    available_config_options = {param.name for param in ctx.command.params}
+    for key in config_keys:
+        if key not in available_config_options:
+            invalid_keys.append(key)
+    if invalid_keys:
+        out(
+            f"Invalid config keys detected: {invalid_keys} in {config_file_path}",
+            fg="red",
+        )
+
+
 def target_version_option_callback(
     c: click.Context, p: Union[click.Option, click.Parameter], v: Tuple[str, ...]
 ) -> List[TargetVersion]:

tests/data/incorrect_spelling.toml

@@ -0,0 +1,5 @@
+[tool.black]
+ine_length = 50
+target-ersion = ['py37']
+exclude='\.pyi?$'
+include='\.py?$'

tests/test_black.py

@@ -106,6 +106,7 @@ class FakeContext(click.Context):
     def __init__(self) -> None:
         self.default_map: Dict[str, Any] = {}
         self.params: Dict[str, Any] = {}
+        self.command: click.Command = black.main
         # Dummy root, since most of the tests don't care about it
         self.obj: Dict[str, Any] = {"root": PROJECT_ROOT}
 
@@ -1538,6 +1539,23 @@ def test_parse_pyproject_toml(self) -> None:
         self.assertEqual(config["exclude"], r"\.pyi?$")
         self.assertEqual(config["include"], r"\.py?$")
 
+    def test_spellcheck_pyproject_toml(self) -> None:
+        test_toml_file = THIS_DIR / "data" / "incorrect_spelling.toml"
+        result = BlackRunner().invoke(
+            black.main,
+            [
+                "--code=print('hello world')",
+                "--verbose",
+                f"--config={str(test_toml_file)}",
+            ],
+        )
+
+        assert (
+            r"Invalid config keys detected: ['ine_length', 'target_ersion'] in "
+            + str(test_toml_file)
+            in result.stderr
+        )
+
     def test_parse_pyproject_toml_project_metadata(self) -> None:
         for test_toml, expected in [
             ("only_black_pyproject.toml", ["py310"]),