Re: [gentoo-dev] RFD: News item format 2.0

[Michał Górny]

On Thu, 14 Jan 2016 07:28:43 -0500
Rich Freeman <rich0@g.o> wrote:

> On Tue, Jan 12, 2016 at 1:13 PM, Ulrich Mueller <ulm@g.o> wrote:
> >
> > Therefore, we could use the opportunity to add some other features.
> > So far, this includes:
> >
>
> I don't have a solution for this in mind, but I do see a problem that
> could use a solution with our current approach to news in our stable
> and unstable branches.
>
> Using the current criteria we have for displaying news items it is
> very hard to prepare a news item that is displayed at an appropriate
> time for both stable and unstable users of a package.  Either the
> unstable users don't get the news item at all, or everybody gets it at
> the same time.  Then stable users end up getting confused and
> eventually forgetting about the notice, only to be hit with the update
> after a significant time lag (it could be a year or more in some
> cases) without any advance news.

I was going to speak about this, and you beat me up to it...

> One way to do this (and I'm certainly open to others) is a
> Display-If-Installable header which takes a keyword string and an atom
> (typically a specific PV).  The package manager would determine if a
> package with that keyword string and PV would be accepted or not based
> on the user's configuration, and if so display the news.  So, if the
> string "~amd64 ~x86", =www-client/apache-2.4.19 were passed, users
> running ~arch would generally get the message, as would a user running
> stable but with <www-client/apache-2.5 in their package.keywords, but
> not a user running stable with <www-client/apache-2.4.19 in their
> package.keywords.  If a user already was running
> www-client/apache-2.4.21 the news would not display since the package
> manager wouldn't attempt to install 2.4.19 if it showed up in the tree
> (I'm open to argument as to whether it should show up if 2.4.19 is
> already installed as there are pros and cons here).  Note that this is
> all hypothetical and the news should be triggered even if 2.4.19 isn't
> in the tree yet, or if it is in the tree with a different set of
> keywords.
>
> Now, this would still potentially require putting the same news item
> into the tree multiple times to trigger it for the unstable/stable
> users, but the key would be that the right users get the message when
> this happens.  Since the details of the news and what PV it applies to
> might change between unstable/stable this is probably appropriate
> anyway.  Likewise if three archs are going stable now and two more a
> year from now the news could be re-triggered just for those archs.
>
> The main downside to this I see is complexity - you can't just set up
> one news item and have it do the right thing.  The main advantage I
> see to this is correctness - it handles both the case where keywords
> are set in make.conf and package.keywords, because it provides enough
> of a hint to the package manager about what is about to be introduced
> into the tree.
>
> There could easily be a better solution for this.  However, I think it
> is a problem worth solving.

...and I think you've found a pretty good solution to the problem.
However, I get lost in your wall of text and I don't really see
the problems you see.

Based on your idea, this is how I'd do it:

1. 'Display-If-Visible' that enables news items if given atom is
visible for PM (i.e. in repo, with right keywords and not masked).
I would avoid using 'Installable' as that could get confusing wrt
conflicts and so on.

2. Combine that with 'Display-If-Installed' -- and we should be able to
get somewhat sane behavior.

For example, for foo-1.0 to -2.0 upgrade notes, we'd do:

  Display-if-installed: <foo-2.0
  Display-if-visible: >=foo-2.0

which would basically mean that all people having old foo installed
would get the item as soon as they foo-2.0 becomes visible to them.
But people installing straight 2.0 without previous versions don't get
the item.

We could also do:

  Display-if-installed: foo
  Display-if-visible: >=foo-2.0

which would cause the item to be displayed to both people who have old
foo installed and can upgrade, or installed 2.0 directly.

-- 
Best regards,
Michał Górny
<http://dev.gentoo.org/~mgorny/>