[PATCH 1 of 8] transaction: introduce "changes" dictionary to precisely track updates

[Yuya Nishihara]

On Wed, 3 May 2017 15:06:05 +0200, Pierre-Yves David wrote:
> On 05/03/2017 09:51 AM, Yuya Nishihara wrote:
> > On Wed, 03 May 2017 01:43:38 +0200, Pierre-Yves David wrote:
> >> # HG changeset patch
> >> # User Pierre-Yves David <pierre-yves.david at ens-lyon.org>
> >> # Date 1493742678 -7200
> >> #      Tue May 02 18:31:18 2017 +0200
> >> # Branch stable
> >> # Node ID 6697da7c4eab3fbe3588a2f91fa3f99b16f808ac
> >> # Parent  fbb5f4bf94928b98fa87871e84bb2ef972ec2d51
> >> # EXP-Topic obscache
> >> # Available At https://www.mercurial-scm.org/repo/users/marmoute/mercurial/
> >> #              hg pull https://www.mercurial-scm.org/repo/users/marmoute/mercurial/ -r 6697da7c4eab
> >> transaction: introduce "changes" dictionary to precisely track updates
> >>
> >> The transaction is already tracking some data intended for hooks (in
> >> 'hookargs'). However, that information is minimal as we optimise for
> >> passing data to other processes through environment variables. There are
> >> multiple places were we could use more complete and lower level
> >> information locally (eg: cache update, better report of changes to
> >> hooks, etc...).
> >>
> >> For this purpose we introduces a 'changes' dictionary on the
> >> transaction.  It is intended to track every changes happening to the
> >> repository (eg: new revs, bookmarks move, phases move, obs-markers,
> >> etc).
> >>
> >> For now we just adds the 'changes' dictionary. We'll adds more tracking
> >> and usages over time.
> >>
> >> diff --git a/mercurial/transaction.py b/mercurial/transaction.py
> >> --- a/mercurial/transaction.py
> >> +++ b/mercurial/transaction.py
> >> @@ -137,6 +137,10 @@ class transaction(object):
> >>              releasefn = lambda tr, success: None
> >>          self.releasefn = releasefn
> >>
> >> +        # A dict dedicated to precisely tracking the changes introduced in the
> >> +        # transaction.
> >> +        self.changes = {}
> >
> > I'm not sure if it's good idea to add more free-form dict to the transaction
> > class, since that would make code less manageable in general.
> 
> Can you elaborate on your worries here?
> 
> The content of the dictionnary should be strictly defined by the 
> localrepo object, and the data should be filled at low level by code 
> that already requires a transaction to be present. So I think the result 
> will be quite manageable.
> 
> We -need- something else than "hookargs" to carry transaction related 
> information. For example we needs to tracks bookmark movement, phases 
> changes and tags movement. The "hookargs" dictionnary is not appropriate 
> to track such data.

My concern is unclear, sorry. The transaction code seems hard to review because
it has arbitrary hooks, weakrefs in them, hookargs dict, etc. And now 'changes'
dict. They all seem to make things too abstract.

I believe the result looks better overall than before, but I can't say the
transaction itself gets better.