Mercurial > hg
view tests/test-pull-r.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 | 1e497df514e2 |
children | 90d997a812dc |
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$ hg init repo $ cd repo $ echo foo > foo $ hg ci -qAm 'add foo' $ echo >> foo $ hg ci -m 'change foo' $ hg up -qC 0 $ echo bar > bar $ hg ci -qAm 'add bar' $ hg log changeset: 2:effea6de0384 tag: tip parent: 0:bbd179dfa0a7 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: add bar changeset: 1:ed1b79f46b9a user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: change foo changeset: 0:bbd179dfa0a7 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: add foo $ cd .. $ hg init copy $ cd copy Pull a missing revision: $ hg pull -qr missing ../repo abort: unknown revision 'missing'! [255] Pull multiple revisions with update: $ hg pull -qu -r 0 -r 1 ../repo $ hg -q parents 0:bbd179dfa0a7 $ hg rollback repository tip rolled back to revision -1 (undo pull) working directory now based on revision -1 $ hg pull -qr 0 ../repo $ hg log changeset: 0:bbd179dfa0a7 tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: add foo $ hg pull -qr 1 ../repo $ hg log changeset: 1:ed1b79f46b9a tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: change foo changeset: 0:bbd179dfa0a7 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: add foo This used to abort: received changelog group is empty: $ hg pull -qr 1 ../repo