tests/logexceptions.py

test: add test-transaction-rollback-on-sigpipe.t demonstrating py3 regression

When an hg push is interrupted with C-c, the remote [hg serve] command
receives SIGPIPE.

If a pretxnchangegroup hook fails, the remote hg then tries to
rollback the transaction. It begins by printing "transaction
abort!\n". This returns EPIPE, but ui.py ignores that error.

In python3 (but not python2), this "transaction abort!\n" message
stays in a buffer, so future flushes of stderr will try to print the
message again, and so those flushes will also hit EPIPE.

This test demonstrates such a case where this EPIPE causes the
transaction rollback to fail, leaving behind an abandoned transaction.

Differential Revision: https://phab.mercurial-scm.org/D9151

# logexceptions.py - Write files containing info about Mercurial exceptions
#
# Copyright 2017 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import inspect
import os
import sys
import traceback
import uuid

from mercurial import (
    dispatch,
    extensions,
)


def handleexception(orig, ui):
    res = orig(ui)

    if not ui.environ.get(b'HGEXCEPTIONSDIR'):
        return res

    dest = os.path.join(
        ui.environ[b'HGEXCEPTIONSDIR'], str(uuid.uuid4()).encode('ascii')
    )

    exc_type, exc_value, exc_tb = sys.exc_info()

    stack = []
    tb = exc_tb
    while tb:
        stack.append(tb)
        tb = tb.tb_next
    stack.reverse()

    hgframe = 'unknown'
    hgline = 'unknown'

    # Find the first Mercurial frame in the stack.
    for tb in stack:
        mod = inspect.getmodule(tb)
        if not mod.__name__.startswith(('hg', 'mercurial')):
            continue

        frame = tb.tb_frame

        try:
            with open(inspect.getsourcefile(tb), 'r') as fh:
                hgline = fh.readlines()[frame.f_lineno - 1].strip()
        except (IndexError, OSError):
            pass

        hgframe = '%s:%d' % (frame.f_code.co_filename, frame.f_lineno)
        break

    primary = traceback.extract_tb(exc_tb)[-1]
    primaryframe = '%s:%d' % (primary.filename, primary.lineno)

    with open(dest, 'wb') as fh:
        parts = [
            str(exc_value),
            primaryframe,
            hgframe,
            hgline,
            ui.environ[b'TESTNAME'].decode('utf-8', 'replace'),
        ]
        fh.write(b'\0'.join(p.encode('utf-8', 'replace') for p in parts))


def extsetup(ui):
    extensions.wrapfunction(dispatch, 'handlecommandexception', handleexception)