mercurial/util.py

Deal with failed clone/transaction interaction

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Deal with failed clone/transaction interaction

> What is happening is that something in the transaction machinery is
> causing the directory to be completely recreated.

The transaction gets rolled back by its destructor. This is critical
so it happens whenever an exception occurs that unwinds the stack.

Unfortunately, what's happening with clone is we're trying to delete
the directory during exception propagation. And a reference to the
transaction is held in the exception backtrace stack frames so it
still exists until the exception is completely resolved.

So there's no way to do the directory delete inside the exception
handling cleanly.

But we can handle it similarly to the transaction itself: use an
object with a destructor.

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# util.py - utility functions and platform specfic implementations
#
# Copyright 2005 K. Thananchayan <[e-mail]>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

import os

class CommandError(Exception): pass

def explain_exit(code):
    """return a 2-tuple (desc, code) describing a process's status"""
    if os.WIFEXITED(code):
        val = os.WEXITSTATUS(code)
        return "exited with status %d" % val, val
    elif os.WIFSIGNALED(code):
        val = os.WTERMSIG(code)
        return "killed by signal %d" % val, val
    elif os.WIFSTOPPED(code):
        val = os.STOPSIG(code)
        return "stopped by signal %d" % val, val
    raise ValueError("invalid exit code")

def system(cmd, errprefix=None):
    """execute a shell command that must succeed"""
    rc = os.system(cmd)
    if rc:
        errmsg = "%s %s" % (os.path.basename(cmd.split(None, 1)[0]),
                            explain_exit(rc)[0])
        if errprefix:
            errmsg = "%s: %s" % (errprefix, errmsg)
        raise CommandError(errmsg)

def rename(src, dst):
    try:
        os.rename(src, dst)
    except:
        os.unlink(dst)
        os.rename(src, dst)

# Platfor specific varients
if os.name == 'nt':
    nulldev = 'NUL:'

    def is_exec(f, last):
        return last

    def set_exec(f, mode):
        pass

    def pconvert(path):
        return path.replace("\\", "/")

    def makelock(info, pathname):
        ld = os.open(pathname, os.O_CREAT | os.O_WRONLY | os.O_EXCL)
        os.write(ld, info)
        os.close(ld)

    def readlock(pathname):
        return file(pathname).read()

else:
    nulldev = '/dev/null'

    def is_exec(f, last):
        return (os.stat(f).st_mode & 0100 != 0)

    def set_exec(f, mode):
        s = os.stat(f).st_mode
        if (s & 0100 != 0) == mode:
            return
        if mode:
            # Turn on +x for every +r bit when making a file executable
            # and obey umask.
            umask = os.umask(0)
            os.umask(umask)
            os.chmod(f, s | (s & 0444) >> 2 & ~umask)
        else:
            os.chmod(f, s & 0666)

    def pconvert(path):
        return path

    def makelock(info, pathname):
        os.symlink(info, pathname)

    def readlock(pathname):
        return os.readlink(pathname)