Unpacking on flow constructs (return/yield) now implies 3.8+ (#2700)

diff --git a/CHANGES.md b/CHANGES.md
index 9208be7cd968e2997e9478ff71a24ef99bcf5e0a..ae0bf80da485ec7d53126c4c346610ab73704efd 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -11,6 +11,7 @@
   (#2686)
 - No longer color diff headers white as it's unreadable in light themed terminals
   (#2691)
+- Tuple unpacking on `return` and `yield` constructs now implies 3.8+ (#2700)
 
 ## 21.12b0
 

diff --git a/src/black/__init__.py b/src/black/__init__.py
index f2efdec83b22a53d1ad00f6d1b1057dcae1f0c0f..08c239dc15561be1ceb41a7411957289880620ac 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -1210,6 +1210,14 @@ def get_features_used(  # noqa: C901
                         if argch.type in STARS:
                             features.add(feature)
 
+        elif (
+            n.type in {syms.return_stmt, syms.yield_expr}
+            and len(n.children) >= 2
+            and n.children[1].type == syms.testlist_star_expr
+            and any(child.type == syms.star_expr for child in n.children[1].children)
+        ):
+            features.add(Feature.UNPACKING_ON_FLOW)
+
         # Python 2 only features (for its deprecation) except for integers, see above
         elif n.type == syms.print_stmt:
             features.add(Feature.PRINT_STMT)

diff --git a/src/black/mode.py b/src/black/mode.py
index a2b7d9e9e2d8708e49e2733aa4811b53c7fc547d..b28dcd8d1494eee4c171b9a58a0f1faea29649e7 100644 (file)
--- a/src/black/mode.py
+++ b/src/black/mode.py
@@ -49,6 +49,7 @@ class Feature(Enum):
     POS_ONLY_ARGUMENTS = 9
     RELAXED_DECORATORS = 10
     PATTERN_MATCHING = 11
+    UNPACKING_ON_FLOW = 12
     FORCE_OPTIONAL_PARENTHESES = 50
 
     # __future__ flags
@@ -116,6 +117,7 @@ VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
         Feature.FUTURE_ANNOTATIONS,
         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.POS_ONLY_ARGUMENTS,
+        Feature.UNPACKING_ON_FLOW,
     },
     TargetVersion.PY39: {
         Feature.UNICODE_LITERALS,
@@ -128,6 +130,7 @@ VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.RELAXED_DECORATORS,
         Feature.POS_ONLY_ARGUMENTS,
+        Feature.UNPACKING_ON_FLOW,
     },
     TargetVersion.PY310: {
         Feature.UNICODE_LITERALS,
@@ -140,6 +143,7 @@ VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.RELAXED_DECORATORS,
         Feature.POS_ONLY_ARGUMENTS,
+        Feature.UNPACKING_ON_FLOW,
         Feature.PATTERN_MATCHING,
     },
 }

diff --git a/tests/test_black.py b/tests/test_black.py
index 63cd716c0bb80aeea9cf31c274ead6b1b930d4e6..8726cc10ddcf13a9c648f32225c32f0bc246fc63 100644 (file)
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -810,6 +810,14 @@ class BlackTestCase(BlackBaseTestCase):
         self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
         node = black.lib2to3_parse("def fn(a, /, b): ...")
         self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
+        node = black.lib2to3_parse("def fn(): yield a, b")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("def fn(): return a, b")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("def fn(): yield *b, c")
+        self.assertEqual(black.get_features_used(node), {Feature.UNPACKING_ON_FLOW})
+        node = black.lib2to3_parse("def fn(): return a, *b, c")
+        self.assertEqual(black.get_features_used(node), {Feature.UNPACKING_ON_FLOW})
 
     def test_get_features_used_for_future_flags(self) -> None:
         for src, features in [