Mercurial > hg
view tests/test-demandimport.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.
author | Greg Ward <greg@gerg.ca> |
---|---|
date | Sun, 24 Apr 2011 19:25:10 -0400 |
parents | c0290fc6b486 |
children | 54af51c18c4c |
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from mercurial import demandimport demandimport.enable() import re rsub = re.sub def f(obj): l = repr(obj) l = rsub("0x[0-9a-fA-F]+", "0x?", l) l = rsub("from '.*'", "from '?'", l) l = rsub("'<[a-z]*>'", "'<whatever>'", l) return l import os print "os =", f(os) print "os.system =", f(os.system) print "os =", f(os) from mercurial import util print "util =", f(util) print "util.system =", f(util.system) print "util =", f(util) print "util.system =", f(util.system) import re as fred print "fred =", f(fred) import sys as re print "re =", f(re) print "fred =", f(fred) print "fred.sub =", f(fred.sub) print "fred =", f(fred) print "re =", f(re) print "re.stderr =", f(re.stderr) print "re =", f(re)