Support sentinel and ast.Compare in ast.literal_eval()

Author: skirpichev

Lib/ast.py

@@ -91,9 +91,16 @@ def _convert_literal(node, omit_validation=False):
         return set(map(_convert_literal, node.elts))
     if (
         isinstance(node, Call) and isinstance(node.func, Name)
-        and node.func.id == 'set' and node.args == node.keywords == []
     ):
-        return set()
+        if node.func.id == 'set' and node.args == node.keywords == []:
+            return set()
+        elif (
+              node.func.id == 'sentinel' and len(node.args) == 1
+              and node.keywords == []
+              and isinstance(arg := node.args[0], Constant)
+              and isinstance(name := arg.value, str)
+        ):
+            return sentinel(name)
     if (
         isinstance(node, UnaryOp)
         and isinstance(node.op, (UAdd, USub))
@@ -116,6 +123,29 @@ def _convert_literal(node, omit_validation=False):
             return left + right
         else:
             return left - right
+    if (isinstance(node, Compare)
+        and isinstance(node.left, Constant)
+        and type(left := _convert_literal(node.left)) in (int, float, str)
+        and len(node.ops) == 1
+        and isinstance(op := node.ops[0], (Eq, NotEq, Lt, LtE, Gt, GtE))
+        and len(node.comparators) == 1
+        and isinstance(node.comparators[0], Constant)
+        and type(right := node.comparators[0].value) in (int, float, str)
+        and (type(left) == type(right) or str not in [type(left), type(right)])
+    ):
+        if isinstance(op, Eq):
+            return left == right
+        elif isinstance(op, NotEq):
+            return left != right
+        elif isinstance(op, Lt):
+            return left < right
+        elif isinstance(op, LtE):
+            return left <= right
+        elif isinstance(op, Gt):
+            return left > right
+        else:
+            return left >= right
+
     msg = "malformed node or string"
     if lno := getattr(node, 'lineno', None):
         msg += f' on line {lno}'

Lib/test/test_ast/test_ast.py

@@ -2032,6 +2032,9 @@ def test_literal_eval(self):
         self.assertEqual(ast.literal_eval('{1, 2, 3}'), {1, 2, 3})
         self.assertEqual(ast.literal_eval('b"hi"'), b"hi")
         self.assertEqual(ast.literal_eval('set()'), set())
+        val = ast.literal_eval('sentinel("xyz")')
+        self.assertTrue(isinstance(val, sentinel))
+        self.assertEqual(val.__name__, "xyz")
         self.assertRaises(ValueError, ast.literal_eval, 'foo()')
         self.assertEqual(ast.literal_eval('6'), 6)
         self.assertEqual(ast.literal_eval('+6'), 6)
@@ -2040,6 +2043,12 @@ def test_literal_eval(self):
         self.assertEqual(ast.literal_eval('+3.25'), 3.25)
         self.assertEqual(ast.literal_eval('-3.25'), -3.25)
         self.assertEqual(repr(ast.literal_eval('-0.0')), '-0.0')
+        self.assertEqual(ast.literal_eval('1 == 2'), False)
+        self.assertEqual(ast.literal_eval('1 != 2'), True)
+        self.assertEqual(ast.literal_eval('1 < 2'), True)
+        self.assertEqual(ast.literal_eval('1 <= 2'), True)
+        self.assertEqual(ast.literal_eval('1 >= 2'), False)
+        self.assertEqual(ast.literal_eval('1 > 2'), False)
         self.assertRaises(ValueError, ast.literal_eval, '++6')
         self.assertRaises(ValueError, ast.literal_eval, '+True')
         self.assertRaises(ValueError, ast.literal_eval, '2+3')