Hi Andres,

Thanks for the reply! Note that I get this message even running 'cabal install' a second time after changing nothing. Is that scenario an example of what you mean by a "potentially dangerous cabal invocation"? I've been unable to avoid this error message by any other means that (a) 'ghc-pkg unregister <package>' or (b) '--force-reinstall'. So far, '--solver=modular' hasn't helped. So I'm hoping for something less aggressive. In particular, in case nothing has changed, I want 'cabal install' to succeed (exit code 0) so that my automated build & install & release processes will continue rather than get stopped.

Regards, - Conal

On Sat, Feb 4, 2012 at 9:51 PM, Andres Löh <andres.loeh@googlemail.com> wrote:
Hi Conal.

On Sun, Feb 5, 2012 at 12:36 AM, Conal Elliott <conal@conal.net> wrote:
> Since upgrading to 7.4.1, if I 'cabal install' successfully and then 'cabal
> install' a second time without first doing a 'ghc-pkg unregister
> <package-name>', I get the following complaint:
>
> [...]

The warning is intended to prevent you from breaking your system
without knowing that you know that you're running a potentially
dangerous cabal invocation.

The --force-reinstalls flag should always make it build. If it
doesn't, it's a bug.

In addition, I'm planning to make the warning a little bit less
aggressive before the release.

> The only path I've found so far that's willing to rebuild or even say
> nothing needs rebuilding (when nothing does) is to 'ghc-pkg unregister' and
> then 'cabal install' again. I'm getting the same behavior on Red Hat 5 and
> Mac OS 10.6.8, both compiled from sources.

I'd be surprised if the OS matters. But as I said, I've not yet
encountered a situation where it wouldn't build given
--force-reinstalls.

Cheers,
 Andres