Satisfy MyPy 0.812 using __all__

MyPy strict mode now disallows implicit re-export.
See fastapi/typer#112 (comment)

src/darker/black_diff.py

@@ -51,6 +51,8 @@
 from black import FileMode as Mode
 from black import TargetVersion, find_pyproject_toml, format_str, parse_pyproject_toml
 
+__all__ = ["BlackArgs", "Mode", "run_black"]
+
 logger = logging.getLogger(__name__)
 
 

src/darker/command_line.py

@@ -29,7 +29,7 @@ def make_argument_parser(require_src: bool) -> ArgumentParser:
     try:
         import isort
     except ImportError:
-        isort = None
+        isort = None  # type: ignore
         description.extend(
             ["", f"{ISORT_INSTRUCTION} to enable sorting of import definitions"]
         )

src/darker/import_sorting.py

@@ -15,8 +15,15 @@
 
 try:
     import isort
+    # Work around Mypy problem
+    # https://github.com/python/mypy/issues/7030#issuecomment-504128883
+    import isort.code as isort_code_
 except ImportError:
-    isort = None
+    isort = None  # type: ignore
+    isort_code_ = None
+isort_code = isort_code_
+
+__all__ = ["apply_isort", "isort"]
 
 logger = logging.getLogger(__name__)
 
@@ -46,4 +53,4 @@ def apply_isort(
             ", ".join(f"{k}={v!r}" for k, v in isort_args.items())
         )
     )
-    return TextDocument.from_str(isort.code(code=content.string, **isort_args))
+    return TextDocument.from_str(isort_code(code=content.string, **isort_args))

src/darker/tests/test_main.py

@@ -39,7 +39,7 @@ def run_isort(git_repo, monkeypatch, caplog, request):
     ), patch("darker.import_sorting.isort.code"):
         darker.__main__.main(["--isort", "./test1.py", *args])
         return SimpleNamespace(
-            isort_code=darker.import_sorting.isort.code, caplog=caplog
+            isort_code=darker.import_sorting.isort_code, caplog=caplog
         )