bpo-43897: AST validation for pattern matching nodes (GH24771)

Lib/test/test_ast.py

@@ -696,7 +696,7 @@ class AST_Tests(unittest.TestCase):
         for constant in "True", "False", "None":
             expr = ast.Expression(ast.Name(constant, ast.Load()))
             ast.fix_missing_locations(expr)
-            with self.assertRaisesRegex(ValueError, f"Name node can't be used with '{constant}' constant"):
+            with self.assertRaisesRegex(ValueError, f"identifier field can't represent '{constant}' constant"):
                 compile(expr, "<test>", "eval")
 
     def test_precedence_enum(self):
@@ -1507,6 +1507,147 @@ class ASTValidatorTests(unittest.TestCase):
                 mod = ast.parse(source, fn)
                 compile(mod, fn, "exec")
 
+    constant_1 = ast.Constant(1)
+    pattern_1 = ast.MatchValue(constant_1)
+
+    constant_x = ast.Constant('x')
+    pattern_x = ast.MatchValue(constant_x)
+
+    constant_true = ast.Constant(True)
+    pattern_true = ast.MatchSingleton(True)
+
+    name_carter = ast.Name('carter', ast.Load())
+
+    _MATCH_PATTERNS = [
+        ast.MatchValue(
+            ast.Attribute(
+                ast.Attribute(
+                    ast.Name('x', ast.Store()),
+                    'y', ast.Load()
+                ),
+                'z', ast.Load()
+            )
+        ),
+        ast.MatchValue(
+            ast.Attribute(
+                ast.Attribute(
+                    ast.Name('x', ast.Load()),
+                    'y', ast.Store()
+                ),
+                'z', ast.Load()
+            )
+        ),
+        ast.MatchValue(
+            ast.Constant(...)
+        ),
+        ast.MatchValue(
+            ast.Constant(True)
+        ),
+        ast.MatchValue(
+            ast.Constant((1,2,3))
+        ),
+        ast.MatchSingleton('string'),
+        ast.MatchSequence([
+          ast.MatchSingleton('string')
+        ]),
+        ast.MatchSequence(
+            [
+                ast.MatchSequence(
+                    [
+                        ast.MatchSingleton('string')
+                    ]
+                )
+            ]
+        ),
+        ast.MatchMapping(
+            [constant_1, constant_true],
+            [pattern_x]
+        ),
+        ast.MatchMapping(
+            [constant_true, constant_1],
+            [pattern_x, pattern_1],
+            rest='True'
+        ),
+        ast.MatchMapping(
+            [constant_true, ast.Starred(ast.Name('lol', ast.Load()), ast.Load())],
+            [pattern_x, pattern_1],
+            rest='legit'
+        ),
+        ast.MatchClass(
+            ast.Attribute(
+                ast.Attribute(
+                    constant_x,
+                    'y', ast.Load()),
+                'z', ast.Load()),
+            patterns=[], kwd_attrs=[], kwd_patterns=[]
+        ),
+        ast.MatchClass(
+            name_carter,
+            patterns=[],
+            kwd_attrs=['True'],
+            kwd_patterns=[pattern_1]
+        ),
+        ast.MatchClass(
+            name_carter,
+            patterns=[],
+            kwd_attrs=[],
+            kwd_patterns=[pattern_1]
+        ),
+        ast.MatchClass(
+            name_carter,
+            patterns=[ast.MatchSingleton('string')],
+            kwd_attrs=[],
+            kwd_patterns=[]
+        ),
+        ast.MatchClass(
+            name_carter,
+            patterns=[ast.MatchStar()],
+            kwd_attrs=[],
+            kwd_patterns=[]
+        ),
+        ast.MatchClass(
+            name_carter,
+            patterns=[],
+            kwd_attrs=[],
+            kwd_patterns=[ast.MatchStar()]
+        ),
+        ast.MatchSequence(
+            [
+                ast.MatchStar("True")
+            ]
+        ),
+        ast.MatchAs(
+            name='False'
+        ),
+        ast.MatchOr(
+            []
+        ),
+        ast.MatchOr(
+            [pattern_1]
+        ),
+        ast.MatchOr(
+            [pattern_1, pattern_x, ast.MatchSingleton('xxx')]
+        )
+    ]
+
+    def test_match_validation_pattern(self):
+        name_x = ast.Name('x', ast.Load())
+        for pattern in self._MATCH_PATTERNS:
+            with self.subTest(ast.dump(pattern, indent=4)):
+                node = ast.Match(
+                    subject=name_x,
+                    cases = [
+                        ast.match_case(
+                            pattern=pattern,
+                            body = [ast.Pass()]
+                        )
+                    ]
+                )
+                node = ast.fix_missing_locations(node)
+                module = ast.Module([node], [])
+                with self.assertRaises(ValueError):
+                    compile(module, "<test>", "exec")
+
 
 class ConstantTests(unittest.TestCase):
     """Tests on the ast.Constant node type."""