[PATCH memctx-cache] memctx: always use cache for filectxfn

[Sean Farley]

FUJIWARA Katsunori <foozy at lares.dti.ne.jp> writes:

> At Sat, 10 Jun 2017 16:01:23 -0700,
> Sean Farley wrote:
>> 
>> # HG changeset patch
>> # User Sean Farley <sean at farley.io>
>> # Date 1497135618 25200
>> #      Sat Jun 10 16:00:18 2017 -0700
>> # Branch memctx-cache
>> # Node ID 12f2faa6019f497ba08960564cfceff80250e75a
>> # Parent  7e9d0d8ff938dcf8ca193c17db5321a05a48e718
>> memctx: always use cache for filectxfn
>> 
>> I don't see a downside to doing this unless I'm missing something.
>> 
>> diff --git a/mercurial/context.py b/mercurial/context.py
>> index 7ce34af..348c13c 100644
>> --- a/mercurial/context.py
>> +++ b/mercurial/context.py
>> @@ -2103,18 +2103,19 @@ class memctx(committablectx):
>>          self._files = files
>>          if branch is not None:
>>              self._extra['branch'] = encoding.fromlocal(branch)
>>          self.substate = {}
>>  
>> +        self._filectxfn = filectxfn
>>          if isinstance(filectxfn, patch.filestore):
>>              self._filectxfn = memfilefrompatch(filectxfn)
>>          elif not callable(filectxfn):
>>              # if store is not callable, wrap it in a function
>>              self._filectxfn = memfilefromctx(filectxfn)
>> -        else:
>> -            # memoizing increases performance for e.g. vcs convert scenarios.
>> -            self._filectxfn = makecachingfilectxfn(filectxfn)
>> +
>> +        # memoizing increases performance for e.g. vcs convert scenarios.
>> +        self._filectxfn = makecachingfilectxfn(filectxfn)
>
> This change seems to cache also results of memfilefrompatch() and
> makecachingfilectxfn(). If so, should makecachingfilectxfn() be
> applied on self._filectxfn ?  Or:
>
> ================
>          self.substate = {}
>  
>          if isinstance(filectxfn, patch.filestore):
> -            self._filectxfn = memfilefrompatch(filectxfn)
> +            filectxfn = memfilefrompatch(filectxfn)
>          elif not callable(filectxfn):
>              # if store is not callable, wrap it in a function
> -            self._filectxfn = memfilefromctx(filectxfn)
> -        else:

The third type of object that can be sent is a function that takes
(repo, memctx, path), so we can't get rid of the 'else:' like this. My
main question in this patch is: can we cache everything from filectxfn?
If not, that's fine (and I would personally document the reason in the
code).
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