handle FileSkipComment

CHANGES.rst

@@ -33,6 +33,7 @@ Fixed
 - Relative paths are now resolved correctly when using the ``--stdout`` option
 - Downgrade to Flake8 version 3.x for Pytest compatibility.
   See `tholo/pytest-flake8#81`__
+- Handle isort file skip comment ``#isort:file_skip`` without an exception
 
 __ https://github.com/tholo/pytest-flake8/issues/81
 

src/darker/import_sorting.py

@@ -72,8 +72,15 @@ def apply_isort(
             ", ".join(f"{k}={v!r}" for k, v in isort_args.items())
         )
     )
+
+    code = content.string
+    try:
+        code = isort_code(code=code, **isort_args)
+    except isort.exceptions.FileSkipComment:
+        pass
+
     return TextDocument.from_str(
-        isort_code(code=content.string, **isort_args),
+        code,
         encoding=content.encoding,
         mtime=content.mtime,
     )

src/darker/tests/test_import_sorting.py

@@ -96,3 +96,15 @@ def test_isort_config(monkeypatch, tmpdir, line_length, settings_file, expect):
         TextDocument.from_str(content), Path("test1.py"), config
     )
     assert actual.string == expect
+
+
+def test_isort_file_skip_comment():
+    """``apply_isort()`` handles ``FileSkipComment`` exception correctly"""
+    # Avoid https://github.com/PyCQA/isort/pull/1833 by splitting the skip string
+    content = "# iso" + "rt:skip_file"
+
+    actual = darker.import_sorting.apply_isort(
+        TextDocument.from_str(content), Path("test1.py")
+    )
+
+    assert actual.string == content