This repository is used to create Docker images that are essentially Haskell compilers, batteries included. It can be compared to a custom Haskell Platform or a custom Stackage snapshot.
For reference, here are the packages obtained the last time I built the image:
> docker run images.reesd.com/reesd/stack > packages.txt
(This contains a fairly recent Hackage subset.)
For Reesd we have a small but growing Haskell code base where we try to create small and reusable programs and libraries. We need that different libraries can be linked together and thus require that we have a consistent set of dependencies.
Because the Haskell packages that we depend on have different versioning policies (e.g. respect or not the PVP), and because it was not a priority to follow all the latest versions, we started to pin some dependencies versions (and live more and more in the past).
This repository is here to help us list (and pin) dependencies, build them together from time to time to detect new incompatibilities, and experiment in trying to adopt more recent packages.
Currently we are using a dummy program with a .cabal file (which list the
dependencies that we want, even if none of them is necessary for the dummy
program).
This is both a cabalized Haskell project and a Docker image. The .cabal file describes a dummy project (i.e. the project is empty and doesn't matter) and gives a list of dependencies to be built together.
When the Docker image is run, it builds the dependencies. This can be done from time to time to make sure everything continues to work together. When the image can't be built, it usually means that some new package has appeared on Hackage, is picked up by Cabal, which ends up in conflict. As conflicts arise, additional packages are pinned.
A Docker container that built the dependencies (see above) can be commited to
an image. That image can be used as a binary distribution of a customized
Haskell Platform, or a batteries-included, self-contained GHC. images/stack
is such a committed container.
First build the Docker image with the dummy Cabal project:
> docker build images/stack-dependencies images/stack-dependencies
Once the image is built, it can be run to cabal update and build all the
dependencies. This is what the second Dockerfile do. Note that the second
Dockerfile refer to the first image as
images.reesd.com/reesd/stack-dependencies. You can either tag it as such, or
change the first line of the second Dockerfile.
> docker build images/stack
...
Successfully built e7d3c36655
Possible usage of the resulting image:
> docker run e7d3c36655 ghc-pkg list
> docker run -t -i e7d3c36655 ghci
> docker run -v `pwd`:/source e7d3c36655 sh -c 'cd /source ; cabal install'
Normally the second image ID is tagged as images.reesd.com/reesd/stack.