On Tue, Feb 25, 2014 at 4:52 PM, Gregory Collins
write down the exact versions of all of the libraries you need in the transitive closure of the dependency graph.
I cobbled together a rudimentary tool that does just that: https://hackage.haskell.org/package/sunlight the idea being that, to my knowledge, there were no tools making it easy to verify that a package builds with the *minimum* specified versions. Typical CI testing will eagerly pull the latest dependencies. sunlight builds in a sandbox, runs your tests, and snapshots the resulting GHC package database. It can do this for multiple GHC versions, and will do one build with the minimum versions possible (it does require that you specify a minimum version for each dependency, but not a maximum). At least then you can consult a record showing the exact package graph that actually worked.