gh-130139: always check ast node type in ast.parse() with ast input

Author: iritkatriel

Doc/whatsnew/3.14.rst

@@ -333,6 +333,10 @@ ast
 * The ``repr()`` output for AST nodes now includes more information.
   (Contributed by Tomas R in :gh:`116022`.)
 
+* ast.parse(), when called with an AST as input, now always verifies
+  that the root node type is appropriate.
+  (Contributed by Irit Katriel in :gh:`130139`.)
+
 
 calendar
 --------

Include/internal/pycore_ast.h

@@ -131,6 +131,12 @@ def test_ast_validation(self):
             tree = ast.parse(snippet)
             compile(tree, '<string>', 'exec')
 
+    def test_parse_invalid_ast(self):
+        # see gh-130139
+        for optval in (-1, 0, 1, 2):
+            self.assertRaises(TypeError, ast.parse, ast.Constant(42),
+                              optimize=optval)
+
     def test_optimization_levels__debug__(self):
         cases = [(-1, '__debug__'), (0, '__debug__'), (1, False), (2, False)]
         for (optval, expected) in cases:

Lib/test/test_ast/test_ast.py

@@ -422,9 +422,9 @@ def test_docstrings(self):
             self.check_ast_roundtrip(f"'''{docstring}'''")
 
     def test_constant_tuples(self):
-        self.check_src_roundtrip(ast.Constant(value=(1,), kind=None), "(1,)")
+        self.check_src_roundtrip(ast.Module([ast.Constant(value=(1,))]), "(1,)")
         self.check_src_roundtrip(
-            ast.Constant(value=(1, 2, 3), kind=None), "(1, 2, 3)"
+            ast.Module([ast.Constant(value=(1, 2, 3))]), "(1, 2, 3)"
         )
 
     def test_function_type(self):

Lib/test/test_unparse.py

@@ -0,0 +1,2 @@
+Fix bug where ``ast.parse`` did not error on AST input which is not of the
+correct type, when called with optimize=False.

Misc/NEWS.d/next/Library/2025-02-15-01-37-47.gh-issue-130139.gntc7B.rst

@@ -2166,18 +2166,13 @@ class PartingShots(StaticVisitor):
 }
 
 /* mode is 0 for "exec", 1 for "eval" and 2 for "single" input */
-mod_ty PyAST_obj2mod(PyObject* ast, PyArena* arena, int mode)
+int PyAst_CheckMode(PyObject *ast, int mode)
 {
     const char * const req_name[] = {"Module", "Expression", "Interactive"};
-    int isinstance;
-
-    if (PySys_Audit("compile", "OO", ast, Py_None) < 0) {
-        return NULL;
-    }
 
     struct ast_state *state = get_ast_state();
     if (state == NULL) {
-        return NULL;
+        return -1;
     }
 
     PyObject *req_type[3];
@@ -2186,13 +2181,30 @@ class PartingShots(StaticVisitor):
     req_type[2] = state->Interactive_type;
 
     assert(0 <= mode && mode <= 2);
-
-    isinstance = PyObject_IsInstance(ast, req_type[mode]);
-    if (isinstance == -1)
-        return NULL;
+    int isinstance = PyObject_IsInstance(ast, req_type[mode]);
+    if (isinstance == -1) {
+        return -1;
+    }
     if (!isinstance) {
         PyErr_Format(PyExc_TypeError, "expected %s node, got %.400s",
                      req_name[mode], _PyType_Name(Py_TYPE(ast)));
+        return -1;
+    }
+    return 0;
+}
+
+mod_ty PyAST_obj2mod(PyObject* ast, PyArena* arena, int mode)
+{
+    if (PySys_Audit("compile", "OO", ast, Py_None) < 0) {
+        return NULL;
+    }
+
+    struct ast_state *state = get_ast_state();
+    if (state == NULL) {
+        return NULL;
+    }
+
+    if (PyAst_CheckMode(ast, mode) < 0) {
         return NULL;
     }
 
@@ -2356,6 +2368,7 @@ def write_header(mod, metadata, f):
     f.write(textwrap.dedent("""
 
         PyObject* PyAST_mod2obj(mod_ty t);
+        int PyAst_CheckMode(PyObject *ast, int mode);
         mod_ty PyAST_obj2mod(PyObject* ast, PyArena* arena, int mode);
         int PyAST_Check(PyObject* obj);
 

Parser/asdl_c.py

@@ -835,6 +835,9 @@ builtin_compile_impl(PyObject *module, PyObject *source, PyObject *filename,
         goto error;
     if (is_ast) {
         if ((flags & PyCF_OPTIMIZED_AST) == PyCF_ONLY_AST) {
+            if (PyAst_CheckMode(source, compile_mode) < 0) {
+                goto error;
+            }
             // return an un-optimized AST
             result = Py_NewRef(source);
         }