Issue #23192: Fixed generator lambdas. Patch by Bruno Cauet.

Author: serhiy-storchaka

Lib/test/test_generators.py

@@ -49,6 +49,26 @@ def gen():
         self.assertTrue(finalized)
         self.assertEqual(gc.garbage, old_garbage)
 
+    def test_lambda_generator(self):
+        # Issue #23192: Test that a lambda returning a generator behaves
+        # like the equivalent function
+        f = lambda: (yield 1)
+        def g(): return (yield 1)
+
+        # test 'yield from'
+        f2 = lambda: (yield from g())
+        def g2(): return (yield from g())
+
+        f3 = lambda: (yield from f())
+        def g3(): return (yield from f())
+
+        for gen_fun in (f, g, f2, g2, f3, g3):
+            gen = gen_fun()
+            self.assertEqual(next(gen), 1)
+            with self.assertRaises(StopIteration) as cm:
+                gen.send(2)
+            self.assertEqual(cm.exception.value, 2)
+
 
 class GeneratorTest(unittest.TestCase):
 

Misc/NEWS

@@ -10,6 +10,8 @@ Release date: 2015-03-28
 Core and Builtins
 -----------------
 
+- Issue #23192: Fixed generator lambdas.  Patch by Bruno Cauet.
+
 - Issue #23629: Fix the default __sizeof__ implementation for variable-sized
   objects.
 

Python/compile.c

@@ -1897,12 +1897,12 @@ compiler_lambda(struct compiler *c, expr_ty e)
     c->u->u_kwonlyargcount = asdl_seq_LEN(args->kwonlyargs);
     VISIT_IN_SCOPE(c, expr, e->v.Lambda.body);
     if (c->u->u_ste->ste_generator) {
-        ADDOP_IN_SCOPE(c, POP_TOP);
+        co = assemble(c, 0);
     }
     else {
         ADDOP_IN_SCOPE(c, RETURN_VALUE);
+        co = assemble(c, 1);
     }
-    co = assemble(c, 1);
     qualname = c->u->u_qualname;
     Py_INCREF(qualname);
     compiler_exit_scope(c);