[Haskell-cafe] Re: Cabal dependency hell

Maciej Piechotka uzytkownik2 at gmail.com
Mon Mar 8 17:31:26 EST 2010

On Mon, 2010-03-08 at 15:37 +0100, Marc Weber wrote:
> Hi Maciej,
> that's why I started hack-nix.
> You can patch dependencies easily.
> However you have to install the Nix package manager.
> It also works with lates versions only because the dependency solves is
> written in Nix itself.
> Which package is causing trouble to you?

For example happstack.

> We can't expect package maintainers to test everything.
> So it must be people like you and me who fixes those changes.

Well. Except that it require bumping versions. Which according to
hackage policy requires to fork a project (which makes it pointless in
the first place)

> The way to go is make hackage allow changing constraints on the fly
> notifying the author that he can update his repository.
> This will work in most cases.
> Bumping versions because a dependency has changed is bad as well.
> This will cause to much overhead (and it dosen't solve the problem
> because the old package is still wrong).
> Specifying dependencies must be decoupled from bumping versions.
> It's because dep specs do depend on the "world" which can change..
> At least that's what I think.

Hmm. When I was returning home I thought about some wiki-like system
that would allow to say 'Package X is compatible/not compatible with Y'.

Possibly something like:
 - Only the 'sure' deps are installed in default mode
 - When in 'expert' mode I can install any package which has not been
marked as incompatible

Then I can say that I tested built and:
 - It failed to built
 - It failed the automatic tests (if they exists)/does not work
 - It success

So if there is versions:
0.7 0.8 0.9 1.0 1.0.1 1.1 1.2 1.3 1.4

 - 0.8 failed to built
 - >=1.0 <1.1 was marked by author
 - 1.1 was marked as success
 - 1.3 failed to build

 - In default/normal mode it can be used with 1.0, 1.0.1 and 1.1
 - In expert mode 0.9 and 1.2 can be installed in addition to above
 - Any version can be installed in 'I'm feeling lucky' mode when I
explicitly say package to ignore some restriction

Possibly it is needed to collect user karma (or possibly already account
verification is sufficient).

> If you're interested in Nix and hack-nix I can show you how everything
> works using an SSH session.

Ekhm... SSH?

> Marc Weber

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