Some possible solutions for the dependency issues

[Chris Moline]

On Sat, Aug 25, 2012 at 6:56 AM, Chris Moline <blackredtree at gmail.com> wrote:
> Hi, so with all the furor over dependency hell I've been thinking
> about how to address the issue. I've come up with an approach that I'm
> willing to try to implement, if it's sensible.

I'd like to elaborate on what I said. A goal of mine is to have every
package using the most recent versions of their dependencies. I have a
script whose basic functionality is mostly finished. What it does is
fetch the latest version of a package, then update its build
dependencies to use the most recent versions and then compile, failing
if there are errors or warnings. If the build fails the most recent
copy of the source code is obtained using the relevant version control
command and I tinker with it trying to get it to compile. If it's too
difficult I stick it in the ignore list, otherwise I generate a patch
and submit it.

This shouldn't take too long because most errors and warnings are
trivial, for example using mkTyCon3 instead of mkTyCon or importing
catch from the right module.

After I make my first pass through the archive I will have a utility
that follows the rss feed and recompiles all packages that depend on
the new package. At this time I will start running any test suites
these packages have and then running hlint on them. I imagine fixing
all the hlint suggestions will take a long time.

So I'm thinking the install strategy for cabal-install could simply be
install the latest versions of the dependencies. Previously installed
packages could continue to use the older versions of dependencies they
were compiled against. We could track whether a package was installed
by the user or automatically as a dependency, that way we could have
an update commmand that will install the latest versions of any
out-of-date packages and any automatically installed packages that are
no longer depended on could then be removed.

So between this script of mine, adapting packages to use explict
versions of libraries and executables, and hard constraints to inhbit
buggy interactions we should be able to have a nice experience with
cabal-install.