pegen (PEP 617): bug in error handling

[vstinner]

BPO	40555
Nosy	@gvanrossum, @vstinner, @lysnikolaou, @pablogsal
PRs	bpo-40555: Check for p->error_indicator in loop rules after the main loop is done #19986

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

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GitHub fields:

assignee = None
closed_at = <Date 2020-05-08.02:39:00.559>
created_at = <Date 2020-05-07.23:48:56.181>
labels = ['interpreter-core', '3.9']
title = 'pegen (PEP 617): bug in error handling'
updated_at = <Date 2020-05-08.02:39:00.559>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2020-05-08.02:39:00.559>
actor = 'pablogsal'
assignee = 'none'
closed = True
closed_date = <Date 2020-05-08.02:39:00.559>
closer = 'pablogsal'
components = ['Interpreter Core']
creation = <Date 2020-05-07.23:48:56.181>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 40555
keywords = ['patch']
message_count = 4.0
messages = ['368391', '368392', '368396', '368408']
nosy_count = 4.0
nosy_names = ['gvanrossum', 'vstinner', 'lys.nikolaou', 'pablogsal']
pr_nums = ['19986']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue40555'
versions = ['Python 3.9']

[vstinner]

autopep8 test suite does crash on Python 3.9.0a6. The bug can be reproduced with:

Python 3.9.0a6+ (heads/master:b7a78ca74a, May  8 2020, 01:46:01) 
[GCC 10.0.1 20200430 (Red Hat 10.0.1-0.14)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> compile('"\\xhh" \\',  '<string>', 'exec', dont_inherit=True)
python: Objects/typeobject.c:984: type_call: Assertion `!_PyErr_Occurred(tstate)' failed.
 Abandon (core dumped)

It seems like p->error_condition should be checked more often in Parser/pegen/parse.c.

[vstinner]

Workaround: use python3.9 -X oldparser.

[lysnikolaou]

That's because we're not checking for errors after a loop is done. Pushing a fix.

[pablogsal]

New changeset db9163c by Pablo Galindo in branch 'master':
bpo-40555: Check for p->error_indicator in loop rules after the main loop is done (GH-19986)
db9163c