Hello everyone, As many of you know, recently I have been working on bringing up infrastructure for using CI-produced binary distributions to build a subset of Hackage using the head.hackage patchset. Happily, this effort has now converged on a usable result, embodied in two merge requests: * https://gitlab.haskell.org/ghc/head.hackage/merge_requests/2 * https://gitlab.haskell.org/ghc/ghc/merge_requests/465 ghc/head.hackage!2 adds CI support to head.hackage. In addition to the usual pass/fail status, this job produces (e.g. [1]) a few additional products: * a JSON summary of the run, describing the dependency graph and pass/fail state of each package. we can feed to an external service to track newly-failing packages. * a (rendered) graphviz graph showing the dependency structure of the built packages, each node colored by its pass/fail state * a tarball of build logs, each including statistics from -ddump-timings. The hope here is that we can use this to track compiler performance on real-world code ghc/ghc!465 adds a job to GHC's own CI pipeline to trigger a head.hackage job using the binary distribution produced earlier in the pipeline. This job will run automatically under a variety of circumstances: * via the scheduled nightly pipeline * on merge requests labelled with the `user-facing` label * when manually started using a button on the MR's Pipelines tab Currently the head.hackage MR tests only a small number of Hackage packages (and their dependencies). Specifically, we currently build `aeson`, `criterion`, `singletons`, `servant`, and `scotty`. This pulls in 127 packages in total. There are a few things that remain to be done: * Better document the existence of the job and how it is triggered * Document how to update the list of tested packages * Work out how to handle tracking of persistent breakage (e.g. we want a notification when a package initially breaks but not in later builds) * Automatically push patched packages to a Hackage repository (e.g. head.hackage.org) as a result of CI. Cheers, - Ben [1] https://gitlab.haskell.org/ghc/head.hackage/-/jobs/38022