perf: introduce safeattrsetter to replace direct attribute assignment
Referring not-existing attribute immediately causes failure, but
assigning a value to such attribute doesn't.
For example, perf.py has code paths below, which assign a value to
not-existing attribute. This causes incorrect performance measurement,
but these code paths are executed successfully.
- "repo._tags = None" in perftags()
recent Mercurial has tags cache information in repo._tagscache
- "branchmap.write = lambda repo: None" in perfbranchmap()
branchmap cache is written out by branchcache.write() in branchmap.py
"util.safehasattr() before assignment" can avoid this issue, but might
increase mistake at "copy & paste" attribute name or so.
To centralize (1) examining existence of, (2) assigning a value to,
and (3) restoring an old value to the attribute, this patch introduces
safeattrsetter(). This is used to replace direct attribute assignment
in subsequent patches.
Encapsulation of restoring is needed to completely remove direct
attribute assignment from perf.py, even though restoring isn't needed
so often.
$ hg init 1
$ echo '[ui]' >> 1/.hg/hgrc
$ echo 'timeout = 10' >> 1/.hg/hgrc
$ echo foo > 1/foo
$ hg --cwd 1 ci -A -m foo
adding foo
$ hg clone 1 2
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg clone 2 3
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat <<EOF > $TESTTMP/debuglocks-pretxn-hook.sh
> hg debuglocks
> true
> EOF
$ echo '[hooks]' >> 2/.hg/hgrc
$ echo "pretxnchangegroup.a = sh $TESTTMP/debuglocks-pretxn-hook.sh" >> 2/.hg/hgrc
$ echo 'changegroup.push = hg push -qf ../1' >> 2/.hg/hgrc
$ echo bar >> 3/foo
$ hg --cwd 3 ci -m bar
$ hg --cwd 3 push ../2 --config devel.legacy.exchange=bundle1
pushing to ../2
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
lock: user *, process * (*s) (glob)
wlock: free
$ hg --cwd 1 --config extensions.strip= strip tip -q
$ hg --cwd 2 --config extensions.strip= strip tip -q
$ hg --cwd 3 push ../2 # bundle2+
pushing to ../2
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
lock: user *, process * (*s) (glob)
wlock: user *, process * (*s) (glob)