comparison mercurial/util.py @ 14007:d764463b433e

atomictempfile: avoid infinite recursion in __del__().

The problem is that a programmer using atomictempfile directly can
make an innocent everyday mistake -- not enough args to the
constructor -- which escalates badly.  You would expect a simple
TypeError crash in that case, but you actually get an infinite
recursion that is surprisingly difficult to kill: it happens between
__del__() and __getattr__(), and Python does not handle infinite
recursion from __del__() well.

The fix is to not implement __getattr__(), but instead assign instance
attributes for the methods we wish to delegate to the builtin file
type: write() and fileno(). I've audited mercurial.* and hgext.* and
found no users of atomictempfile using methods other than write() and
rename(). I audited third-party extensions and found one (snap)
passing an atomictempfile to util.fstat(), so I also threw in
fileno().

The last time I submitted a similar patch, Matt proposed that we make
atomictempfile a subclass of file instead of wrapping it. Rejected on
grounds of unnecessary complexity: for one thing, it would make the
Windows implementation of posixfile quite a bit more complex. It would
have to become a subclass of file rather than a simple function -- but
since it's written in C, this is non-obvious and non-trivial.
Furthermore, there's nothing wrong with wrapping objects and
delegating methods: it's a well-established pattern that works just
fine in many cases. Subclassing is not the answer to all of life's
problems.

14006:a395575691a6

    All writes will be redirected to a temporary copy of the original
    file.  When rename is called, the copy is renamed to the original
    name, making the changes visible.
    """
    def __init__(self, name, mode='w+b', createmode=None):
        self.__name = name
        self._fp = None
        self.temp = mktempcopy(name, emptyok=('w' in mode),
                               createmode=createmode)
        self._fp = posixfile(self.temp, mode)

    def __getattr__(self, name):
        return getattr(self._fp, name)

    def rename(self):
        if not self._fp.closed:
            self._fp.close()
            rename(self.temp, localpath(self.__name))

    def close(self):
        if not self._fp:
            return
        if not self._fp.closed:
            try:
                os.unlink(self.temp)
            except: pass
            self._fp.close()

    def __del__(self):
        self.close()

def makedirs(name, mode=None):
    """recursive directory creation with parent mode inheritance"""
    parent = os.path.abspath(os.path.dirname(name))
    try:

14007:d764463b433e

    All writes will be redirected to a temporary copy of the original
    file.  When rename is called, the copy is renamed to the original
    name, making the changes visible.
    """
    def __init__(self, name, mode='w+b', createmode=None):
        self.__name = name      # permanent name
        self._tempname = mktempcopy(name, emptyok=('w' in mode),
                                    createmode=createmode)
        self._fp = posixfile(self._tempname, mode)

        # delegated methods
        self.write = self._fp.write
        self.fileno = self._fp.fileno

    def rename(self):
        if not self._fp.closed:
            self._fp.close()
            rename(self._tempname, localpath(self.__name))

    def close(self):
        if not self._fp.closed:
            try:
                os.unlink(self._tempname)
            except OSError:
                pass
            self._fp.close()

    def __del__(self):
        if hasattr(self, '_fp'): # constructor actually did something
            self.close()

def makedirs(name, mode=None):
    """recursive directory creation with parent mode inheritance"""
    parent = os.path.abspath(os.path.dirname(name))
    try: