Deprecate Python 2 formatting support (#2523)

* Prepare for Python 2 depreciation

- Use BlackRunner and .stdout in command line test

So the next commit won't break this test. This is in its own commit so
we can just revert the depreciation commit when dropping Python 2
support completely.

* Deprecate Python 2 formatting support

diff --git a/CHANGES.md b/CHANGES.md
index 4c04eccde48f26a786f15a9e7d2fb34bd945d75d..9990d8cf459ea8fadf19153b5bc019b280aa08cb 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -10,6 +10,7 @@
 - Bumped typed-ast version minimum to 1.4.3 for 3.10 compatiblity (#2519)
 - Fixed a Python 3.10 compatibility issue where the loop argument was still being passed
   even though it has been removed (#2580)
+- Deprecate Python 2 formatting support (#2523)
 
 ### _Blackd_
 

diff --git a/docs/faq.md b/docs/faq.md
index 9fe53922b6d7e56bce269a6fdaae0e59ee7db150..77f9df51fd4ad1413e2c160f8b9cafb70a7c4f8e 100644 (file)
--- a/docs/faq.md
+++ b/docs/faq.md
@@ -74,13 +74,17 @@ disabled-by-default counterpart W504. E203 should be disabled while changes are
 
 ## Does Black support Python 2?
 
+```{warning}
+Python 2 support has been deprecated since 21.10b0.
+
+This support will be dropped in the first stable release, expected for January 2022.
+See [The Black Code Style](the_black_code_style/index.rst) for details.
+```
+
 For formatting, yes! [Install](getting_started.md#installation) with the `python2` extra
 to format Python 2 files too! In terms of running _Black_ though, Python 3.6 or newer is
 required.
 
-Note that this support will be dropped in the first stable release, expected for
-January 2022. See [The Black Code Style](the_black_code_style/index.rst) for details.
-
 ## Why does my linter or typechecker complain after I format my code?
 
 Some linters and other tools use magical comments (e.g., `# noqa`, `# type: ignore`) to

diff --git a/src/black/__init__.py b/src/black/__init__.py
index c503c1a55f78d9be7088c571572334d9f7cd837e..831cda934a86449f1b033a14ac614daffa35ba26 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -1061,6 +1061,15 @@ def format_str(src_contents: str, *, mode: Mode) -> FileContent:
         versions = mode.target_versions
     else:
         versions = detect_target_versions(src_node)
+
+    # TODO: fully drop support and this code hopefully in January 2022 :D
+    if TargetVersion.PY27 in mode.target_versions or versions == {TargetVersion.PY27}:
+        msg = (
+            "DEPRECATION: Python 2 support will be removed in the first stable release"
+            "expected in January 2022."
+        )
+        err(msg, fg="yellow", bold=True)
+
     normalize_fmt_off(src_node)
     lines = LineGenerator(
         mode=mode,
@@ -1103,7 +1112,7 @@ def decode_bytes(src: bytes) -> Tuple[FileContent, Encoding, NewLine]:
         return tiow.read(), encoding, newline
 
 
-def get_features_used(node: Node) -> Set[Feature]:
+def get_features_used(node: Node) -> Set[Feature]:  # noqa: C901
     """Return a set of (relatively) new Python features used in this file.
 
     Currently looking for:
@@ -1113,6 +1122,7 @@ def get_features_used(node: Node) -> Set[Feature]:
     - positional only arguments in function signatures and lambdas;
     - assignment expression;
     - relaxed decorator syntax;
+    - print / exec statements;
     """
     features: Set[Feature] = set()
     for n in node.pre_order():
@@ -1161,6 +1171,11 @@ def get_features_used(node: Node) -> Set[Feature]:
                         if argch.type in STARS:
                             features.add(feature)
 
+        elif n.type == token.PRINT_STMT:
+            features.add(Feature.PRINT_STMT)
+        elif n.type == token.EXEC_STMT:
+            features.add(Feature.EXEC_STMT)
+
     return features
 
 

diff --git a/src/black/mode.py b/src/black/mode.py
index 0b7624eaf8ae5fad9f81d7cabde094709119847f..374c47a42eb0a661e28eb097dccb17e102582a3a 100644 (file)
--- a/src/black/mode.py
+++ b/src/black/mode.py
@@ -41,9 +41,17 @@ class Feature(Enum):
     RELAXED_DECORATORS = 10
     FORCE_OPTIONAL_PARENTHESES = 50
 
+    # temporary for Python 2 deprecation
+    PRINT_STMT = 200
+    EXEC_STMT = 201
+
 
 VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
-    TargetVersion.PY27: {Feature.ASYNC_IDENTIFIERS},
+    TargetVersion.PY27: {
+        Feature.ASYNC_IDENTIFIERS,
+        Feature.PRINT_STMT,
+        Feature.EXEC_STMT,
+    },
     TargetVersion.PY33: {Feature.UNICODE_LITERALS, Feature.ASYNC_IDENTIFIERS},
     TargetVersion.PY34: {Feature.UNICODE_LITERALS, Feature.ASYNC_IDENTIFIERS},
     TargetVersion.PY35: {

diff --git a/src/blib2to3/pgen2/token.py b/src/blib2to3/pgen2/token.py
index 1e0dec9c714d9c5cf518e863e1087761f77a5253..349ba8023a27110bba09f145f763157909995351 100644 (file)
--- a/src/blib2to3/pgen2/token.py
+++ b/src/blib2to3/pgen2/token.py
@@ -74,6 +74,9 @@ ERRORTOKEN: Final = 58
 COLONEQUAL: Final = 59
 N_TOKENS: Final = 60
 NT_OFFSET: Final = 256
+# temporary for Python 2 deprecation
+PRINT_STMT: Final = 316
+EXEC_STMT: Final = 288
 # --end constants--
 
 tok_name: Final[Dict[int, str]] = {}

diff --git a/tests/test_black.py b/tests/test_black.py
index 5647a00e48ba99a38184f180faa3ee578c8efc02..b96a54385576ba9e458629df3a5ee7b6cfc89200 100644 (file)
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -1401,14 +1401,14 @@ class BlackTestCase(BlackBaseTestCase):
         )
         expected = 'def foo():\n    """Testing\n    Testing"""\n    print "Foo"\n'
 
-        result = CliRunner().invoke(
+        result = BlackRunner().invoke(
             black.main,
             ["-", "-q", "--target-version=py27"],
             input=BytesIO(source),
         )
 
         self.assertEqual(result.exit_code, 0)
-        actual = result.output
+        actual = result.stdout
         self.assertFormatEqual(actual, expected)
 
     @staticmethod
@@ -2017,6 +2017,21 @@ class TestFileCollection:
         )
 
 
+@pytest.mark.parametrize("explicit", [True, False], ids=["explicit", "autodetection"])
+def test_python_2_deprecation_with_target_version(explicit: bool) -> None:
+    args = [
+        "--config",
+        str(THIS_DIR / "empty.toml"),
+        str(DATA_DIR / "python2.py"),
+        "--check",
+    ]
+    if explicit:
+        args.append("--target-version=py27")
+    with cache_dir():
+        result = BlackRunner().invoke(black.main, args)
+    assert "DEPRECATION: Python 2 support will be removed" in result.stderr
+
+
 with open(black.__file__, "r", encoding="utf-8") as _bf:
     black_source_lines = _bf.readlines()