sending non-None values makes generator raise StopIteration on next access

[Zabolekar]

BPO	46009
Nosy	@tiran, @markshannon, @pablogsal, @brandtbucher, @Zabolekar
PRs	bpo-46009: Do not exhaust generator when send() method raises #29986 [3.10] bpo-46009: Do not exhaust generator when send() method raises (GH-29986). #29988 bpo-46009: Remove GEN_START #30367

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2022-01-05.16:02:13.606>
created_at = <Date 2021-12-07.21:53:29.521>
labels = ['type-bug', 'release-blocker', '3.10', '3.11']
title = 'sending non-None values makes generator raise StopIteration on next access'
updated_at = <Date 2022-01-05.16:02:13.606>
user = 'https://github.com/Zabolekar'

bugs.python.org fields:

activity = <Date 2022-01-05.16:02:13.606>
actor = 'christian.heimes'
assignee = 'none'
closed = True
closed_date = <Date 2022-01-05.16:02:13.606>
closer = 'christian.heimes'
components = []
creation = <Date 2021-12-07.21:53:29.521>
creator = 'Zabolekar'
dependencies = []
files = []
hgrepos = []
issue_num = 46009
keywords = ['patch']
message_count = 7.0
messages = ['407975', '408013', '408021', '409700', '409770', '409776', '409781']
nosy_count = 5.0
nosy_names = ['christian.heimes', 'Mark.Shannon', 'pablogsal', 'brandtbucher', 'Zabolekar']
pr_nums = ['29986', '29988', '30367']
priority = 'release blocker'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue46009'
versions = ['Python 3.10', 'Python 3.11']

[Zabolekar]

Tested with Python 3.10.1 on Linux and Python 3.10.0 on Windows.

The following code prints None in 3.9 and raises StopIteration without any additional information in 3.10:

    def f():
        yield
    
    x = f()
    
    try:
        x.send(0)
    except TypeError as e:
        print(e) # can't send non-None value to a just-started generator
    
    print(next(x))

[markshannon]

New changeset 69806b9 by Mark Shannon in branch 'main':
bpo-46009: Do not exhaust generator when send() method raises (GH-29986)
69806b9

[pablogsal]

New changeset 99c7232 by Mark Shannon in branch '3.10':
[3.10] bpo-46009: Do not exhaust generator when send() method raises (GH-29986). (GH-29988)
99c7232

[brandtbucher]

New changeset 31e43cb by Brandt Bucher in branch 'main':
bpo-46009: Remove GEN_START (GH-30367)
31e43cb

[tiran]

#74552 broke Emscripten WASM builds. I'm getting a "null function or function signature mismatch" error from the WASM engine:

RuntimeError: null function or function signature mismatch
at _PyEval_EvalFrameDefault (http://localhost:8000/python.wasm:wasm-function[2383]:0x103a6f)
at gen_send_ex2 (http://localhost:8000/python.wasm:wasm-function[886]:0x4f35d)
at gen_iternext (http://localhost:8000/python.wasm:wasm-function[893]:0x4fb1a)
at builtin_any (http://localhost:8000/python.wasm:wasm-function[3927]:0x198a87)
at cfunction_vectorcall_O (http://localhost:8000/python.wasm:wasm-function[403]:0x201ae)
at PyObject_Vectorcall (http://localhost:8000/python.wasm:wasm-function[2426]:0x109dbe)
at _PyEval_EvalFrameDefault (http://localhost:8000/python.wasm:wasm-function[2383]:0x1062ba)
at _PyEval_Vector (http://localhost:8000/python.wasm:wasm-function[2380]:0xfc366)
at PyEval_EvalCode (http://localhost:8000/python.wasm:wasm-function[2379]:0xfc014)
at _PyConfig_InitPathConfig (http://localhost:8000/python.wasm:wasm-function[6871]:0x2924b0)

I'm trying to get more debug information now.