From f7917453c99f8183ffd0397affcccb2c37594771 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Sun, 10 Sep 2023 16:12:20 -0700
Subject: [PATCH 1/1] Re-export black.Mode (#3875)

---
 src/black/__init__.py | 11 +++--------
 tests/test_black.py   | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/src/black/__init__.py b/src/black/__init__.py
index 6fc91d2..188a4f7 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -63,14 +63,9 @@ from black.handle_ipynb_magics import (
 )
 from black.linegen import LN, LineGenerator, transform_line
 from black.lines import EmptyLineTracker, LinesBlock
-from black.mode import (
-    FUTURE_FLAG_TO_FEATURE,
-    VERSION_TO_FEATURES,
-    Feature,
-    Mode,
-    TargetVersion,
-    supports_feature,
-)
+from black.mode import FUTURE_FLAG_TO_FEATURE, VERSION_TO_FEATURES, Feature
+from black.mode import Mode as Mode  # re-exported
+from black.mode import TargetVersion, supports_feature
 from black.nodes import (
     STARS,
     is_number_token,
diff --git a/tests/test_black.py b/tests/test_black.py
index badb8ff..d22b685 100644
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -2482,6 +2482,41 @@ class TestFileCollection:
         )
 
 
+class TestDeFactoAPI:
+    """Test that certain symbols that are commonly used externally keep working.
+
+    We don't (yet) formally expose an API (see issue #779), but we should endeavor to
+    keep certain functions that external users commonly rely on working.
+
+    """
+
+    def test_format_str(self) -> None:
+        # format_str and Mode should keep working
+        assert (
+            black.format_str("print('hello')", mode=black.Mode()) == 'print("hello")\n'
+        )
+
+        # you can pass line length
+        assert (
+            black.format_str("print('hello')", mode=black.Mode(line_length=42))
+            == 'print("hello")\n'
+        )
+
+        # invalid input raises InvalidInput
+        with pytest.raises(black.InvalidInput):
+            black.format_str("syntax error", mode=black.Mode())
+
+    def test_format_file_contents(self) -> None:
+        # You probably should be using format_str() instead, but let's keep
+        # this one around since people do use it
+        assert (
+            black.format_file_contents("x=1", fast=True, mode=black.Mode()) == "x = 1\n"
+        )
+
+        with pytest.raises(black.NothingChanged):
+            black.format_file_contents("x = 1\n", fast=True, mode=black.Mode())
+
+
 try:
     with open(black.__file__, "r", encoding="utf-8") as _bf:
         black_source_lines = _bf.readlines()
-- 
2.39.5