[Haskell-cafe] Cabal problem, broken packages?

[Brandon Allbery]

The problem with the old way of doing things is exactly what you're
seeing: conflicting package versions that interfere with each other.
Cabal and stack both know how to expose only the package versions
needed by a build, while retaining all versions needed by various
build environments.

On Thu, Sep 15, 2022 at 12:39 PM Volker Wysk <post at volker-wysk.de> wrote:
>
> Am Donnerstag, dem 15.09.2022 um 12:25 -0400 schrieb Brandon Allbery:
> > It looks good because you're using it the way you're supposed to
> > instead of blindly using --lib to install things. That creates
> > dependency issues like what you're having. Basically, don't use --lib
> > unless you know what you're doing.
> >
> > Remove the environment file, and create projects with dependencies on
> > the libraries you want, instead of trying to preinstall them. Cabal
> > knows how to manage packages for you so they don't conflict.
>
> I admit that I don't really know what I'm doing, when using cabal. I've
> built my projects by calling ghc from a generic Makefile for a long time
> now. And you're saying I should build them with "cabal build" instead? This
> would mean that I must change my long-fostered build environment.
>
> Looks like I have to do some reading.
>
> Bye,
> Volker
>
> >
> > On Thu, Sep 15, 2022 at 12:12 PM Volker Wysk <post at volker-wysk.de> wrote:
> > >
> > > Am Donnerstag, dem 15.09.2022 um 16:31 +0100 schrieb Tom Ellis:
> > > > On Thu, Sep 15, 2022 at 05:23:10PM +0200, Volker Wysk wrote:
> > > > > I've lately set up the Haskell environment on my Linux box, with no
> > > > > problems. Then I have installed some packages with "cabal install", again
> > > > > without problems. But now I'm trying to install another package and I get a
> > > > > dependency conflict. It doesn't seem to matter which package I try to
> > > > > install:
> > > >
> > > > This is quite weird, because neither directory nor ghc are
> > > > dependencies of rfc5051.
> > > >
> > > > As a first step, can you try the following and report back whether you
> > > > successfully get to a GHCi a prompt?
> > > >
> > > > $ cabal repl -z --build-depends rfc5051
> > >
> > > This results in:
> > >
> > >
> > > desktop ~ $ cabal repl -z --build-depends rfc5051
> > > Resolving dependencies...
> > > Build profile: -w ghc-8.8.4 -O1
> > > In order, the following will be built (use -v for more details):
> > >  - rfc5051-0.2 (lib) (requires download & build)
> > >  - fake-package-0 (lib) (first run)
> > > Downloading  rfc5051-0.2
> > > Downloaded   rfc5051-0.2
> > > Starting     rfc5051-0.2 (lib)
> > > Building     rfc5051-0.2 (lib)
> > > Installing   rfc5051-0.2 (lib)
> > > Completed    rfc5051-0.2 (lib)
> > > Configuring library for fake-package-0..
> > > Preprocessing library for fake-package-0..
> > > Warning: No exposed modules
> > > GHCi, version 8.8.4: https://www.haskell.org/ghc/  :? for help
> > > Loaded GHCi configuration from /tmp/cabal-repl.-17863/setcwd.ghci
> > > Prelude>
> > >
> > >
> > > Looks good, doesn't it..?
> > >
> > > Volker
> > > _______________________________________________
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> >
> >
> >
>


-- 
brandon s allbery kf8nh
allbery.b at gmail.com