From: David Bremner <david@tethera.net>
To: Austin Clements <amdragon@mit.edu>
Subject: Re: [PATCH v3 04/13] lib: Database version 3: Introduce fine-grained
	"features"
In-Reply-To: <20140824221629.GP3015@mit.edu>
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	<87ppfqsv8s.fsf@maritornes.cs.unb.ca>
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	<87zjeu4jyp.fsf@maritornes.cs.unb.ca> <20140824221629.GP3015@mit.edu>
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Date: Sun, 24 Aug 2014 16:03:23 -0700
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Austin Clements <amdragon@mit.edu> writes:

> Quoth David Bremner on Aug 23 at  8:58 pm:
>> Austin Clements <amdragon@mit.edu> writes:
>> 
>> >>> @@ -1048,7 +1164,8 @@ notmuch_database_get_version (notmuch_database_t *notmuch)
>> >>>  notmuch_bool_t
>> >>>  notmuch_database_needs_upgrade (notmuch_database_t *notmuch)
>> >>>  {
>> >>> -    return notmuch->needs_upgrade;
>> >>> +    return notmuch->mode == NOTMUCH_DATABASE_MODE_READ_WRITE &&
>> >>> +	(NOTMUCH_FEATURES_CURRENT & ~notmuch->features);
>> >>>  }
>> >>
>> >> Maybe I'm not thinking hard enough here, but how does this deal with a
>> >> feature that is needed to open a database in read only mode? Maybe it
>> >> needs a comment for people not as clever as Austin ;).
>> >
>> > I'm not quite sure what you mean.  notmuch_database_needs_upgrade
>> > returns false for read-only databases because you can't upgrade a
>> > read-only database.  This was true before this patch, too, though it was
>> > less obvious.  (Maybe that's not what you're asking?)
>> 
>> Yes, that's what I was asking. I guess it's orthogonal to your patch
>> series, but the logic of returning FALSE for read only databases is not
>> very intuitive to me (in the sense that "needs upgrade" is not the
>> opposite of "can't be upgraded".  Your new comment later in the series
>> is better, but it would IMHO be even better if you mentioned the read
>> only case.
>
> That's a good point.  Ideally this should be
> "notmuch_database_can_upgrade" or something, which I think would
> capture exactly what it means after this series.  However, I don't
> think it's worth breaking API compatibility given that this is already
> how callers use this function (even though that violates the current
> library spec).
>
> So, how's this for a more updated doc comment on needs_upgrade?

LGTM