mark: avoid ast.Name for True/False/None (debug build crash) [swev-id: pytest-dev__pytest-7324]

src/_pytest/compat.py

@@ -1,6 +1,7 @@
 """
 python version compatibility code
 """
+import ast
 import enum
 import functools
 import inspect
@@ -33,7 +34,7 @@
 
 
 if TYPE_CHECKING:
-    from typing import Type
+    from typing import Type  # noqa: F401 (used in type string)
     from typing_extensions import Final
 
 
@@ -60,6 +61,22 @@ class NotSetType(enum.Enum):
     import importlib_metadata  # noqa: F401
 
 
+_LITERAL_IDENTS = {
+    "True": True,
+    "False": False,
+    "None": None,
+}
+
+
+def _ident_to_name(name: str) -> ast.expr:
+    if name in _LITERAL_IDENTS:
+        literal = _LITERAL_IDENTS[name]
+        if sys.version_info >= (3, 8):
+            return ast.Constant(value=literal)
+        return ast.NameConstant(value=literal)
+    return ast.Name(id=name, ctx=ast.Load())
+
+
 def _format_args(func: Callable[..., Any]) -> str:
     return str(signature(func))
 

src/_pytest/mark/expression.py

@@ -27,7 +27,7 @@
 
 import attr
 
-from _pytest.compat import TYPE_CHECKING
+from _pytest.compat import TYPE_CHECKING, _ident_to_name
 
 if TYPE_CHECKING:
     from typing import NoReturn
@@ -129,7 +129,7 @@ def reject(self, expected: Sequence[TokenType]) -> "NoReturn":
 
 def expression(s: Scanner) -> ast.Expression:
     if s.accept(TokenType.EOF):
-        ret = ast.NameConstant(False)  # type: ast.expr
+        ret = _ident_to_name("False")
     else:
         ret = expr(s)
         s.accept(TokenType.EOF, reject=True)
@@ -161,7 +161,7 @@ def not_expr(s: Scanner) -> ast.expr:
         return ret
     ident = s.accept(TokenType.IDENT)
     if ident:
-        return ast.Name(ident.value, ast.Load())
+        return _ident_to_name(ident.value)
     s.reject((TokenType.NOT, TokenType.LPAREN, TokenType.IDENT))
 
 

testing/test_mark_expression.py

@@ -128,8 +128,6 @@ def test_syntax_errors(expr: str, column: int, message: str) -> None:
         "not[and]or",
         "1234+5678",
         "123.232",
-        "True",
-        "False",
         "if",
         "else",
         "while",
@@ -139,6 +137,17 @@ def test_valid_idents(ident: str) -> None:
     assert evaluate(ident, {ident: True}.__getitem__)
 
 
+@pytest.mark.parametrize(
+    ("expr", "expected"),
+    (("True", True), ("False", False), ("None", None)),
+)
+def test_literal_idents(expr: str, expected: object) -> None:
+    def _unexpected_lookup(ident: str) -> bool:
+        pytest.fail("unexpected lookup for {!r}".format(ident))
+
+    assert evaluate(expr, _unexpected_lookup) is expected
+
+
 @pytest.mark.parametrize(
     "ident",
     (