procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
# sshprotoext.py - Extension to test behavior of SSH protocol
#
# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
# This extension replaces the SSH server started via `hg serve --stdio`.
# The server behaves differently depending on environment variables.
from mercurial import (
error,
extensions,
registrar,
sshpeer,
wireprotoserver,
wireprotov1server,
)
configtable = {}
configitem = registrar.configitem(configtable)
configitem(b'sshpeer', b'mode', default=None)
configitem(b'sshpeer', b'handshake-mode', default=None)
class bannerserver(wireprotoserver.sshserver):
"""Server that sends a banner to stdout."""
def serve_forever(self):
for i in range(10):
self._fout.write(b'banner: line %d\n' % i)
super(bannerserver, self).serve_forever()
class prehelloserver(wireprotoserver.sshserver):
"""Tests behavior when connecting to <0.9.1 servers.
The ``hello`` wire protocol command was introduced in Mercurial
0.9.1. Modern clients send the ``hello`` command when connecting
to SSH servers. This mock server tests behavior of the handshake
when ``hello`` is not supported.
"""
def serve_forever(self):
l = self._fin.readline()
assert l == b'hello\n'
# Respond to unknown commands with an empty reply.
wireprotoserver._sshv1respondbytes(self._fout, b'')
l = self._fin.readline()
assert l == b'between\n'
proto = wireprotoserver.sshv1protocolhandler(
self._ui, self._fin, self._fout
)
rsp = wireprotov1server.dispatch(self._repo, proto, b'between')
wireprotoserver._sshv1respondbytes(self._fout, rsp.data)
super(prehelloserver, self).serve_forever()
def performhandshake(orig, ui, stdin, stdout, stderr):
"""Wrapped version of sshpeer._performhandshake to send extra commands."""
mode = ui.config(b'sshpeer', b'handshake-mode')
if mode == b'pre-no-args':
ui.debug(b'sending no-args command\n')
stdin.write(b'no-args\n')
stdin.flush()
return orig(ui, stdin, stdout, stderr)
elif mode == b'pre-multiple-no-args':
ui.debug(b'sending unknown1 command\n')
stdin.write(b'unknown1\n')
ui.debug(b'sending unknown2 command\n')
stdin.write(b'unknown2\n')
ui.debug(b'sending unknown3 command\n')
stdin.write(b'unknown3\n')
stdin.flush()
return orig(ui, stdin, stdout, stderr)
else:
raise error.ProgrammingError(b'unknown HANDSHAKECOMMANDMODE: %s' % mode)
def extsetup(ui):
# It's easier for tests to define the server behavior via environment
# variables than config options. This is because `hg serve --stdio`
# has to be invoked with a certain form for security reasons and
# `dummyssh` can't just add `--config` flags to the command line.
servermode = ui.environ.get(b'SSHSERVERMODE')
if servermode == b'banner':
wireprotoserver.sshserver = bannerserver
elif servermode == b'no-hello':
wireprotoserver.sshserver = prehelloserver
elif servermode:
raise error.ProgrammingError(b'unknown server mode: %s' % servermode)
peermode = ui.config(b'sshpeer', b'mode')
if peermode == b'extra-handshake-commands':
extensions.wrapfunction(sshpeer, '_performhandshake', performhandshake)
elif peermode:
raise error.ProgrammingError(b'unknown peer mode: %s' % peermode)