contrib/hgclient.py

rust: module policy with importrust

We introduce two rust+c module policies and a new
`policy.importrust()` that makes use of them.

This simple approach provides runtime switching of
implementations, which is crucial for the performance
measurements such as those Octobus does with ASV.

It can also be useful for bug analysis.

It also has the advantage of making conditionals in
Rust callers more uniform, in particular
abstracting over specifics like `demandimport`

At this point, the build stays unchanged, with the rust-cpython based
`rustext` module being built if HGWITHRUSTEXT=cpython.

More transparency for the callers, i.e., just using
`policy.importmod` would be a much longer term and riskier
effort for the following reasons:

1. It would require to define common module boundaries
   for the three or four cases (pure, c, rust+ext, cffi) and that
   is premature with the Rust extension currently under heavy
   development in areas that are outside the scope of the C extensions.
2. It would imply internal API changes that are not currently wished,
   as the case of ancestors demonstrates.
3. The lack of data or property-like attributes (tp_member
   and tp_getset) in current `rust-cpython` makes it impossible to
   achieve direct transparent replacement of pure Python classes by
   Rust extension code, meaning that the caller sometimes has to be able
   to make adjustments or provide additional wrapping.

# A minimal client for Mercurial's command server

from __future__ import absolute_import, print_function

import io
import os
import re
import signal
import socket
import struct
import subprocess
import sys
import time

if sys.version_info[0] >= 3:
    stdout = sys.stdout.buffer
    stderr = sys.stderr.buffer
    stringio = io.BytesIO
    def bprint(*args):
        # remove b'' as well for ease of test migration
        pargs = [re.sub(br'''\bb(['"])''', br'\1', b'%s' % a) for a in args]
        stdout.write(b' '.join(pargs) + b'\n')
else:
    import cStringIO
    stdout = sys.stdout
    stderr = sys.stderr
    stringio = cStringIO.StringIO
    bprint = print

def connectpipe(path=None, extraargs=()):
    cmdline = [b'hg', b'serve', b'--cmdserver', b'pipe']
    if path:
        cmdline += [b'-R', path]
    cmdline.extend(extraargs)

    def tonative(cmdline):
        if os.name != r'nt':
            return cmdline
        return [arg.decode("utf-8") for arg in cmdline]

    server = subprocess.Popen(tonative(cmdline), stdin=subprocess.PIPE,
                              stdout=subprocess.PIPE)

    return server

class unixconnection(object):
    def __init__(self, sockpath):
        self.sock = sock = socket.socket(socket.AF_UNIX)
        sock.connect(sockpath)
        self.stdin = sock.makefile('wb')
        self.stdout = sock.makefile('rb')

    def wait(self):
        self.stdin.close()
        self.stdout.close()
        self.sock.close()

class unixserver(object):
    def __init__(self, sockpath, logpath=None, repopath=None):
        self.sockpath = sockpath
        cmdline = [b'hg', b'serve', b'--cmdserver', b'unix', b'-a', sockpath]
        if repopath:
            cmdline += [b'-R', repopath]
        if logpath:
            stdout = open(logpath, 'a')
            stderr = subprocess.STDOUT
        else:
            stdout = stderr = None
        self.server = subprocess.Popen(cmdline, stdout=stdout, stderr=stderr)
        # wait for listen()
        while self.server.poll() is None:
            if os.path.exists(sockpath):
                break
            time.sleep(0.1)

    def connect(self):
        return unixconnection(self.sockpath)

    def shutdown(self):
        os.kill(self.server.pid, signal.SIGTERM)
        self.server.wait()

def writeblock(server, data):
    server.stdin.write(struct.pack(b'>I', len(data)))
    server.stdin.write(data)
    server.stdin.flush()

def readchannel(server):
    data = server.stdout.read(5)
    if not data:
        raise EOFError
    channel, length = struct.unpack('>cI', data)
    if channel in b'IL':
        return channel, length
    else:
        return channel, server.stdout.read(length)

def sep(text):
    return text.replace(b'\\', b'/')

def runcommand(server, args, output=stdout, error=stderr, input=None,
               outfilter=lambda x: x):
    bprint(b'*** runcommand', b' '.join(args))
    stdout.flush()
    server.stdin.write(b'runcommand\n')
    writeblock(server, b'\0'.join(args))

    if not input:
        input = stringio()

    while True:
        ch, data = readchannel(server)
        if ch == b'o':
            output.write(outfilter(data))
            output.flush()
        elif ch == b'e':
            error.write(data)
            error.flush()
        elif ch == b'I':
            writeblock(server, input.read(data))
        elif ch == b'L':
            writeblock(server, input.readline(data))
        elif ch == b'm':
            bprint(b"message: %r" % data)
        elif ch == b'r':
            ret, = struct.unpack('>i', data)
            if ret != 0:
                bprint(b' [%d]' % ret)
            return ret
        else:
            bprint(b"unexpected channel %c: %r" % (ch, data))
            if ch.isupper():
                return

def check(func, connect=connectpipe):
    stdout.flush()
    server = connect()
    try:
        return func(server)
    finally:
        server.stdin.close()
        server.wait()

def checkwith(connect=connectpipe, **kwargs):
    def wrap(func):
        return check(func, lambda: connect(**kwargs))
    return wrap