some tests

src/black/__init__.py

@@ -545,7 +545,8 @@ def main( # noqa: C901
  out(main.get_usage(ctx) + "\n\nOne of 'SRC' or 'code' is required.")
  ctx.exit(1)
 
- if enable_unstable_feature and not preview:
+ # It doesn't do anything if --unstable is also passed, so just allow it.
+ if enable_unstable_feature and not (preview or unstable):
  out(
  main.get_usage(ctx)
  + "\n\n'--enable-unstable-feature' requires '--preview'."

tests/test_black.py

@@ -1402,6 +1402,22 @@ def get_output(*args: Any, **kwargs: Any) -> io.TextIOWrapper:
  pass # StringIO does not support detach
  assert output.getvalue() == expected
 
+ def test_cli_unstable(self) -> None:
+ self.invokeBlack(["--unstable", "-c", "0"], exit_code=0)
+ self.invokeBlack(["--preview", "-c", "0"], exit_code=0)
+ # Must also pass --preview
+ self.invokeBlack(
+ ["--enable-unstable-feature", "string_processing", "-c", "0"], exit_code=1
+ )
+ self.invokeBlack(
+ ["--preview", "--enable-unstable-feature", "string_processing", "-c", "0"],
+ exit_code=0,
+ )
+ self.invokeBlack(
+ ["--unstable", "--enable-unstable-feature", "string_processing", "-c", "0"],
+ exit_code=0,
+ )
+
  def test_invalid_cli_regex(self) -> None:
  for option in ["--include", "--exclude", "--extend-exclude", "--force-exclude"]:
  self.invokeBlack(["-", option, "**()(!!*)"], exit_code=2)