Address picnixz review: restore divmod line, use set literal, add deferred-attrs test

Author: arpittkhandelwal

Lib/_pydecimal.py

@@ -1501,8 +1501,7 @@ def __divmod__(self, other, context=None):
                 return ans, ans
             else:
                 with context._defer_traps():
-                    return (context._raise_error(DivisionByZero, 'x // 0',
-                                                 sign),
+                    return (context._raise_error(DivisionByZero, 'x // 0', sign),
                             context._raise_error(InvalidOperation, 'x % 0'))
 
         quotient, remainder = self._divide(other, context)
@@ -4064,7 +4063,7 @@ def __setattr__(self, name, value):
             return object.__setattr__(self, name, value)
         elif name == 'flags' or name == 'traps':
             return self._set_signal_dict(name, value)
-        elif name in ('_ignored_flags', '_deferred_traps', '_deferred_error'):
+        elif name in {'_ignored_flags', '_deferred_traps', '_deferred_error'}:
             return object.__setattr__(self, name, value)
         else:
             raise AttributeError(

Lib/test/test_decimal.py

@@ -4287,6 +4287,30 @@ def test_signaldict_repr(self):
 class PyContextFlags(ContextFlags, unittest.TestCase):
     decimal = P
 
+    def test_deferred_traps_attributes(self):
+        # The _defer_traps state lives in the _deferred_traps and
+        # _deferred_error attributes, which __setattr__ must accept.
+        Context = self.decimal.Context
+        Decimal = self.decimal.Decimal
+        Overflow = self.decimal.Overflow
+        context = Context(prec=9, Emin=-999, Emax=999, traps=[])
+        self.assertEqual(context._deferred_traps, 0)
+        self.assertIsNone(context._deferred_error)
+        context._deferred_traps = 1
+        context._deferred_traps = 0
+        context._deferred_error = Overflow('test')
+        context._deferred_error = None
+        with self.assertRaises(AttributeError):
+            context._no_such_attribute = 1
+
+        # A trapped operation resets the state, so the context
+        # remains usable afterwards.
+        context.traps[Overflow] = 1
+        with self.assertRaises(Overflow):
+            context.multiply(Decimal('1E+800'), Decimal('1E+800'))
+        self.assertEqual(context._deferred_traps, 0)
+        self.assertIsNone(context._deferred_error)
+
 class SpecialContexts:
     """Test the context templates."""