bpo-41218: Only mark async code with CO_COROUTINE. (#21357)

3.8.3 had a regression where compiling with ast.PyCF_ALLOW_TOP_LEVEL_AWAIT woudl agressively mark things are coroutine even if there were not.

Author: Carreau

Lib/test/test_builtin.py

@@ -371,6 +371,25 @@ def f(): """doc"""
  rv = ns['f']()
  self.assertEqual(rv, tuple(expected))
 
+ def test_compile_top_level_await_no_coro(self):
+ """Make sure top level non-await codes get the correct coroutine flags.
+ """
+ modes = ('single', 'exec')
+ code_samples = [
+ '''def f():pass\n''',
+ '''[x for x in l]'''
+ ]
+ for mode, code_sample in product(modes, code_samples):
+ source = dedent(code_sample)
+ co = compile(source,
+ '?',
+ mode,
+ flags=ast.PyCF_ALLOW_TOP_LEVEL_AWAIT)
+
+ self.assertNotEqual(co.co_flags & CO_COROUTINE, CO_COROUTINE,
+ msg=f"source={source} mode={mode}")
+
+
  def test_compile_top_level_await(self):
  """Test whether code some top level await can be compiled.
 

Misc/NEWS.d/next/Core and Builtins/2020-07-06-13-35-17.bpo-41218.oKnSr2.rst

@@ -0,0 +1,4 @@
+Python 3.8.3 had a regression where compiling with
+ast.PyCF_ALLOW_TOP_LEVEL_AWAIT would aggressively mark list comprehension
+with CO_COROUTINE. Now only list comprehension making use of async/await
+will tagged as so.

Python/compile.c

@@ -4588,10 +4588,9 @@ compiler_comprehension(struct compiler *c, expr_ty e, int type,
  comprehension_ty outermost;
  PyObject *qualname = NULL;
  int is_async_generator = 0;
+ int top_level_await = IS_TOP_LEVEL_AWAIT(c);
+
 
- if (IS_TOP_LEVEL_AWAIT(c)) {
- c->u->u_ste->ste_coroutine = 1;
- }
  int is_async_function = c->u->u_ste->ste_coroutine;
 
  outermost = (comprehension_ty) asdl_seq_GET(generators, 0);
@@ -4603,7 +4602,7 @@ compiler_comprehension(struct compiler *c, expr_ty e, int type,
 
  is_async_generator = c->u->u_ste->ste_coroutine;
 
- if (is_async_generator && !is_async_function && type != COMP_GENEXP) {
+ if (is_async_generator && !is_async_function && type != COMP_GENEXP && !top_level_await) {
  compiler_error(c, "asynchronous comprehension outside of "
  "an asynchronous function");
  goto error_in_scope;
@@ -4642,6 +4641,9 @@ compiler_comprehension(struct compiler *c, expr_ty e, int type,
  qualname = c->u->u_qualname;
  Py_INCREF(qualname);
  compiler_exit_scope(c);
+ if (top_level_await && is_async_generator){
+ c->u->u_ste->ste_coroutine = 1;
+ }
  if (co == NULL)
  goto error;