Skip to content

Multiple Home Units

Matthew Pickering requested to merge wip/mp-multi-hmi into master

Here for CI. Seems to be basically working 😎


  • Dependencies between home units

  • Solution for Template Haskell splices assuming that compilation is relative to directory with cabal file

  • Allow specifying module visibility for home package units

  • Make package imports work with home units by adding a flag which informs GHC about what the package would be called, if it were one.

  • Consistently use cwd for runProgram rather than rewriting paths

  • Adds tests for -I and -optP-include

  • Warnings for bad situations, which I need to think about

  • Error for not loading a package in between two home units (p -> q -> r)

  • Testing testing testing (tested loading lens and all dependencies, works fine).

Known Shortcomings (these should become issues)

  • Think about how to deal with reexported modules, not sure how Cabal handles these, will probably leave unsupported in first iteration.
  • Currently two backpack tests fail because HoleUnit doesn't distinguish when home unit it should be from.
  • Loading wired-in packages (such as template-haskell) currently fails due to how wired-in packages get different -this-unit-id. Will probably leave unsupported as only template-haskell is really affected.
  • Package thinning/renaming is not supported
  • More complicated reexported (with renaming) not working
  • Backpack almost certainly doesn't work with multiple home units, completely untested.
  • Downsweep should be parallelized, it is quite slow with 1800 modules/139 packages.
  • Some existing shortcomings with ghci (#20474 (closed) #20689) which are exposed more by this patch.

Future Work

  • Rewrite .bkp mode to use multiple home units.
  • Allow GHCi to load multiple home units, simple mode, one "main" unit, the rest depend on it.
  • Should -working-dir offset source paths passed on the command line? (For example should C.hs be interpreted as work-dir/C.hs).(yes)
Edited by Matthew Pickering

Merge request reports