bpo-35975: Support parsing earlier minor versions of Python 3 (GH-12086)

This adds a `feature_version` flag to `ast.parse()` (documented) and `compile()` (hidden) that allow tweaking the parser to support older versions of the grammar. In particular if `feature_version` is 5 or 6, the hacks for the `async` and `await` keyword from PEP 492 are reinstated. (For 7 or higher, these are unconditionally treated as keywords, but they are still special tokens rather than `NAME` tokens that the parser driver recognizes.)



https://bugs.python.org/issue35975

1 files changed, 6 insertions, 0 deletions

diff --git a/Parser/asdl_c.py b/Parser/asdl_c.py
index 1526995e3f8..52247559d1a 100644
--- a/Parser/asdl_c.py
+++ b/Parser/asdl_c.py
@@ -1189,6 +1189,11 @@ PyObject* PyAST_mod2obj(mod_ty t)
 /* mode is 0 for "exec", 1 for "eval" and 2 for "single" input */
 mod_ty PyAST_obj2mod(PyObject* ast, PyArena* arena, int mode)
 {
+    return PyAST_obj2mod_ex(ast, arena, mode, PY_MINOR_VERSION);
+}
+
+mod_ty PyAST_obj2mod_ex(PyObject* ast, PyArena* arena, int mode, int feature_version)
+{
     mod_ty res;
     PyObject *req_type[3];
     char *req_name[] = {"Module", "Expression", "Interactive"};
@@ -1269,6 +1274,7 @@ def main(srcfile, dump_module=False):
             f.write("\n")
             f.write("PyObject* PyAST_mod2obj(mod_ty t);\n")
             f.write("mod_ty PyAST_obj2mod(PyObject* ast, PyArena* arena, int mode);\n")
+            f.write("mod_ty PyAST_obj2mod_ex(PyObject* ast, PyArena* arena, int mode, int feature_version);\n")
             f.write("int PyAST_Check(PyObject* obj);\n")
             f.write('\n')
             f.write('#ifdef __cplusplus\n')