Re: Why are depends rebuilt on "bmake update" ?

[Alan Barrett <apb%cequrux.com@localhost>]

On Thu, 25 Oct 2012, Aleksej Saushev wrote:
> Consider the following scenario.
> There're two packages installed, A and B, A depends on B.
>
>   A -> B
>
> Now, B gets updated but A lags behind, instead B1 is introduced.
>
> When running pkg_rr something triggers update of B.
> It gets rebuilt, replaced, and triggers update of A.
> Now the dependecies look like this:
>
>   A -> [B1, yet to build]
>        B
>
> If B and B1 conflict, user is in trouble.
> If B is high enough in forest, going back is even harder.

Yes, that can easily happen.  I have most often seen it when a package
is split.  For example:

   T1:  You install usefulpkg-1.0, which depends on sometool-1.0

   T2:  sometool version 2 is released, and pkgsrc decides to
        split it into sometool-base-2.0 and sometool-2.0,
        with sometool-2.0 depending on sometool-base-2.0.

        sometool-base-2.0 is marked as conflicting with sometool-1.0.

        pkgsrc changes usefulpkg-1.0nb1 to depend on sometool-base-2.0,
        where usefulpkg-1.0 used to depend on sometool-1.0.

   T3:  You update your pkgsrc tree, and run pkg_rr.

        pkg_rr wants to upgrade usefulpkg from version 1.0 to 1.0nb1.

        pkg_rr needs to build sometool-base-2.0 as a dependency for
        usefulpkg-1.0nb1

        sometool-base-2.0 can't be installed, because it conflicts with
        sometool-1.0.

   T4:  You figure out what's wrong, manually delete sometool-1.0,
        run pkg_rr again, and now it works.

--apb (Alan Barrett)