[Haskell-cafe] Hiding platform packages in Cabal sandboxes

[Michal Antkiewicz]

AFAIK there's no way to selectively "hide" packages. However, you might be
able to use cabal2nix4dev [1]. You'll have to modify the nix expressions to
use your packages instead of the existing ones from the platform (in NIX
they can happily coexist).

Perhaps somebody with direct NIX experience could provide more detailed
step by step instructions?

Michal

[1] https://github.com/dave4420/cabal2nix4dev




On Wed, Oct 15, 2014 at 9:07 AM, Sven Panne <svenpanne at gmail.com> wrote:

> As a maintainer of the various OpenGL-related packages I have the
> following problem: The Haskell platform has those packages (OpenGLRaw,
> GLURaw, ...) exposed, which is the right thing to do in general. When
> I want to work on those packages, I'd like to use Cabal sandboxes to
> avoid screwing up the platform versions of them, but things get a bit
> tricky then. Consider e.g. the GLURaw package, which depends on the
> OpenGLRaw package. Assume that I'd like to add some stuff to the
> OpenGLRaw package and use that in GLURaw. With cabal sandboxes I'll
> have to fight a little bit, because versions of these packages are
> already exposed:
>
>
> -----------------------------------------------------------------------------------------------------------------------
> svenpanne at svenpanne[master]:~/repos/haskell-packages/GLURaw$ cabal
> sandbox init
> Writing a default package environment file to
>
> /usr/local/google/home/svenpanne/repos/haskell-packages/GLURaw/cabal.sandbox.config
> Creating a new sandbox at
>
> /usr/local/google/home/svenpanne/repos/haskell-packages/GLURaw/.cabal-sandbox
> svenpanne at svenpanne[master]:~/repos/haskell-packages/GLURaw$ cabal
> sandbox add-source ../OpenGLRaw
>
> -----------------------------------------------------------------------------------------------------------------------
>
> No problem so far. But the next step is not so OK:
>
>
> -----------------------------------------------------------------------------------------------------------------------
> svenpanne at svenpanne[master]:~/repos/haskell-packages/GLURaw$ cabal
> install --only-dependencies
> Resolving dependencies...
> All the requested packages are already installed:
> Use --reinstall if you want to reinstall anyway.
>
> -----------------------------------------------------------------------------------------------------------------------
>
> Hmmm, obviously cabal sees the globally exposed OpenGLRaw and ignores
> that I've done add-source above. OK, next try with --constraint added:
>
>
> -----------------------------------------------------------------------------------------------------------------------
> svenpanne at svenpanne[master]:~/repos/haskell-packages/GLURaw$ cabal
> install --only-dependencies --constraint='OpenGLRaw source'
> Resolving dependencies...
> In order, the following would be installed:
> OpenGLRaw-1.5.0.0 (reinstall)
> cabal: The following packages are likely to be broken by the reinstalls:
> OpenGL-2.9.2.0
> GLUT-2.5.1.1
> GLURaw-1.4.0.1
> Use --force-reinstalls if you want to install anyway.
>
> -----------------------------------------------------------------------------------------------------------------------
>
> (Is there any documentation about --constraint? I figured that out by
> actually reading the cabal sources. :-/ ) Better, but still not OK, so
> let's add --force-reinstalls:
>
>
> -----------------------------------------------------------------------------------------------------------------------
> svenpanne at svenpanne[master]:~/repos/haskell-packages/GLURaw$ cabal
> install --only-dependencies --constraint='OpenGLRaw source'
> --force-reinstalls
> Resolving dependencies...
> Warning: The following packages are likely to be broken by the reinstalls:
> OpenGL-2.9.2.0
> GLUT-2.5.1.1
> GLURaw-1.4.0.1
> Continuing even though the plan contains dangerous reinstalls.
> Notice: installing into a sandbox located at
>
> /usr/local/google/home/svenpanne/repos/haskell-packages/GLURaw/.cabal-sandbox
> Configuring OpenGLRaw-1.5.0.0...
> Building OpenGLRaw-1.5.0.0...
> Installed OpenGLRaw-1.5.0.0
>
> -----------------------------------------------------------------------------------------------------------------------
>
> That works, so after that I could actually build/install GLURaw. So in
> a nutshell what I have to do is:
>
>    cabal sandbox init
>    cabal sandbox add-source ../OpenGLRaw
>    cabal install --constraint='OpenGLRaw source' --force-reinstalls
> --enable-documentation --haddock-hyperlink-source
>
> And for other packages I even have to add several --constraint flags,
> because they depend on several locally modified packages. This seems a
> bit weird. Is this the recommended workflow? How do other maintainers
> of platform packages handle this? What one *actually* wants is hiding
> some of the globally exposed packages while being in the sandbox
> (--constraint and --force-reinstalls could go away then), but I've
> found no way to do that.
>
> Cheers,
>    S.
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