perform yield from delegation by repeating YIELD_FROM opcode (closes #14230)

This allows generators that are using yield from to be seen by debuggers. It
also kills the f_yieldfrom field on frame objects.

Patch mostly from Mark Shannon with a few tweaks by me.

2 files changed, 23 insertions, 2 deletions

diff --git a/Lib/test/test_pep380.py b/Lib/test/test_pep380.py
index bdcfacd..658bcb9 100644
--- a/Lib/test/test_pep380.py
+++ b/Lib/test/test_pep380.py
@@ -10,7 +10,7 @@ see <http://www.cosc.canterbury.ac.nz/greg.ewing/python/yield-from/YieldFrom-Pyt
 import unittest
 import io
 import sys
-import traceback
+import inspect
 import parser
 
 from test.support import captured_stderr
@@ -919,6 +919,27 @@ class TestPEP380Operation(unittest.TestCase):
         next(g1)
         g1.close()
 
+    def test_delegator_is_visible_to_debugger(self):
+        def call_stack():
+            return [f[3] for f in inspect.stack()]
+
+        def gen():
+            yield call_stack()
+            yield call_stack()
+            yield call_stack()
+
+        def spam(g):
+            yield from g
+
+        def eggs(g):
+            yield from g
+
+        for stack in spam(gen()):
+            self.assertTrue('spam' in stack)
+
+        for stack in spam(eggs(gen())):
+            self.assertTrue('spam' in stack and 'eggs' in stack)
+
 
 def test_main():
     from test import support
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 9f6af7f..2afc261 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -730,7 +730,7 @@ class SizeofTest(unittest.TestCase):
         nfrees = len(x.f_code.co_freevars)
         extras = x.f_code.co_stacksize + x.f_code.co_nlocals +\
                   ncells + nfrees - 1
-        check(x, size(vh + '13P3i' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
+        check(x, size(vh + '12P3i' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
         # function
         def func(): pass
         check(func, size(h + '12P'))