Mercurial > hg
view tests/test-template-engine.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 | dc6b9b3bf63e |
children | f2719b387380 |
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$ cat > engine.py << EOF > > from mercurial import templater > > class mytemplater(object): > def __init__(self, loader, filters, defaults): > self.loader = loader > > def process(self, t, map): > tmpl = self.loader(t) > for k, v in map.iteritems(): > if k in ('templ', 'ctx', 'repo', 'revcache', 'cache'): > continue > if hasattr(v, '__call__'): > v = v(**map) > v = templater.stringify(v) > tmpl = tmpl.replace('{{%s}}' % k, v) > yield tmpl > > templater.engines['my'] = mytemplater > EOF $ hg init test $ echo '[extensions]' > test/.hg/hgrc $ echo "engine = `pwd`/engine.py" >> test/.hg/hgrc $ cd test $ cat > mymap << EOF > changeset = my:changeset.txt > EOF $ cat > changeset.txt << EOF > {{rev}} {{node}} {{author}} > EOF $ hg ci -Ama adding changeset.txt adding mymap $ hg log --style=./mymap 0 97e5f848f0936960273bbf75be6388cd0350a32b test