ui: add special-purpose atexit functionality
In spite of its longstanding use, Python's built-in atexit code is
not suitable for Mercurial's purposes, for several reasons:
* Handlers run after application code has finished.
* Because of this, the code that runs handlers swallows exceptions
(since there's no possible stacktrace to associate errors with).
If we're lucky, we'll get something spat out to stderr (if stderr
still works), which of course isn't any use in a big deployment
where it's important that exceptions get logged and aggregated.
* Mercurial's current atexit handlers make unfortunate assumptions
about process state (specifically stdio) that, coupled with the
above problems, make it impossible to deal with certain categories
of error (try "hg status > /dev/full" on a Linux box).
* In Python 3, the atexit implementation is completely hidden, so
we can't hijack the platform's atexit code to run handlers at a
time of our choosing.
As a result, here's a perfectly cromulent atexit-like implementation
over which we have control. This lets us decide exactly when the
handlers run (after each request has completed), and control what
the process state is when that occurs (and afterwards).
#require killdaemons
$ hgserve() {
> hg serve -a localhost -p $HGPORT1 -d --pid-file=hg.pid \
> -E errors.log -v $@ > startup.log
> # Grepping hg serve stdout would hang on Windows
> grep -v 'listening at' startup.log
> cat hg.pid >> "$DAEMON_PIDS"
> }
$ hg init a
$ hg --encoding utf-8 -R a branch æ
marked working directory as branch \xc3\xa6 (esc)
(branches are permanent and global, did you want a bookmark?)
$ echo foo > a/foo
$ hg -R a ci -Am foo
adding foo
$ hgserve -R a --config web.push_ssl=False --config web.allow_push=* --encoding latin1
$ hg --encoding utf-8 clone http://localhost:$HGPORT1 b
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
updating to branch \xc3\xa6 (esc)
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg --encoding utf-8 -R b log
changeset: 0:867c11ce77b8
branch: \xc3\xa6 (esc)
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: foo
$ echo bar >> b/foo
$ hg -R b ci -m bar
$ hg --encoding utf-8 -R b push
pushing to http://localhost:$HGPORT1/
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 1 changesets with 1 changes to 1 files
$ hg -R a --encoding utf-8 log
changeset: 1:58e7c90d67cb
branch: \xc3\xa6 (esc)
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: bar
changeset: 0:867c11ce77b8
branch: \xc3\xa6 (esc)
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: foo
$ killdaemons.py hg.pid
verify 7e7d56fe4833 (encoding fallback in branchmap to maintain compatibility with 1.3.x)
$ cat <<EOF > oldhg
> import sys
> from mercurial import ui, hg, commands
>
> class StdoutWrapper(object):
> def __init__(self, stdout):
> self._file = stdout
>
> def write(self, data):
> if data == '47\n':
> # latin1 encoding is one %xx (3 bytes) shorter
> data = '44\n'
> elif data.startswith('%C3%A6 '):
> # translate to latin1 encoding
> data = '%%E6 %s' % data[7:]
> self._file.write(data)
>
> def __getattr__(self, name):
> return getattr(self._file, name)
>
> sys.stdout = StdoutWrapper(sys.stdout)
> sys.stderr = StdoutWrapper(sys.stderr)
>
> myui = ui.ui.load()
> repo = hg.repository(myui, 'a')
> commands.serve(myui, repo, stdio=True, cmdserver=False)
> EOF
$ echo baz >> b/foo
$ hg -R b ci -m baz
$ hg push -R b -e 'python oldhg' ssh://dummy/ --encoding latin1
pushing to ssh://dummy/
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 1 changesets with 1 changes to 1 files