Mercurial > hg
view tests/test-custom-filters.t @ 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 | 4134686b83e1 |
children | 56b2bcea2529 |
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$ hg init $ cat > .hg/hgrc <<EOF > [extensions] > prefixfilter = prefix.py > [encode] > *.txt = stripprefix: Copyright 2046, The Masters > [decode] > *.txt = insertprefix: Copyright 2046, The Masters > EOF $ cat > prefix.py <<EOF > from mercurial import util > def stripprefix(s, cmd, filename, **kwargs): > header = '%s\n' % cmd > if s[:len(header)] != header: > raise util.Abort('missing header "%s" in %s' % (cmd, filename)) > return s[len(header):] > def insertprefix(s, cmd): > return '%s\n%s' % (cmd, s) > def reposetup(ui, repo): > repo.adddatafilter('stripprefix:', stripprefix) > repo.adddatafilter('insertprefix:', insertprefix) > EOF $ cat > .hgignore <<EOF > .hgignore > prefix.py > prefix.pyc > EOF $ cat > stuff.txt <<EOF > Copyright 2046, The Masters > Some stuff to ponder very carefully. > EOF $ hg add stuff.txt $ hg ci -m stuff Repository data: $ hg cat stuff.txt Some stuff to ponder very carefully. Fresh checkout: $ rm stuff.txt $ hg up -C 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cat stuff.txt Copyright 2046, The Masters Some stuff to ponder very carefully. $ echo "Very very carefully." >> stuff.txt $ hg stat M stuff.txt $ echo "Unauthorized material subject to destruction." > morestuff.txt Problem encoding: $ hg add morestuff.txt $ hg ci -m morestuff abort: missing header "Copyright 2046, The Masters" in morestuff.txt [255] $ hg stat M stuff.txt A morestuff.txt