bpo-38870: Don't omit parenthesis when unparsing a slice in ast.unparse

When unparsing a non-empty tuple, the parentheses can be safely
omitted if there aren't any elements that explicitly require them (such as starred expressions).

1 files changed, 9 insertions, 1 deletions

diff --git a/Lib/test/test_unparse.py b/Lib/test/test_unparse.py
index 6d82872..bb725ce 100644
--- a/Lib/test/test_unparse.py
+++ b/Lib/test/test_unparse.py
@@ -279,10 +279,13 @@ class UnparseTestCase(ASTTestCase):
         self.check_ast_roundtrip(r"""{**{'y': 2}, 'x': 1}""")
         self.check_ast_roundtrip(r"""{**{'y': 2}, **{'x': 1}}""")
 
-    def test_ext_slices(self):
+    def test_slices(self):
         self.check_ast_roundtrip("a[i]")
         self.check_ast_roundtrip("a[i,]")
         self.check_ast_roundtrip("a[i, j]")
+        self.check_ast_roundtrip("a[(*a,)]")
+        self.check_ast_roundtrip("a[(a:=b)]")
+        self.check_ast_roundtrip("a[(a:=b,c)]")
         self.check_ast_roundtrip("a[()]")
         self.check_ast_roundtrip("a[i:j]")
         self.check_ast_roundtrip("a[:j]")
@@ -470,6 +473,11 @@ class CosmeticTestCase(ASTTestCase):
         for prefix in ("not",):
             self.check_src_roundtrip(f"{prefix} 1")
 
+    def test_slices(self):
+        self.check_src_roundtrip("a[1]")
+        self.check_src_roundtrip("a[1, 2]")
+        self.check_src_roundtrip("a[(1, *a)]")
+
 class DirectoryTestCase(ASTTestCase):
     """Test roundtrip behaviour on all files in Lib and Lib/test."""