State of support

• The core functionality of haskell-language-server is supported.
• Only some plugins and formatters needs to be updated to make it work with ghc-9.0.1 so they are not included until then.
• So you should consider use other ghc version only if you are specially interested in those plugins o formatters

Has ghc-9.0 support

• ghcide
• haskell-language-server
• hls-haddock-comments-plugin
• hls-hlint-plugin
• hls-importlens-plugin
• hls-pragmas-plugin
• hls-retrie-plugin
• hls-eval-plugin Eval plugin: support ghc 9.0.1 #1997
• hls-module-name-plugin - Actually builds just fine. Was accidentally disabled
• hls-class-plugin - Class plugin bump up #2475
• hls-refine-imports-plugin - All deps build
• hls-splice-plugin - All deps build
• hls-tactic-plugin
  • Blocked upstream by ghc-source-gen (Support GHC 9 google/ghc-source-gen#77 / Add GHC 9 support google/ghc-source-gen#84)
  • Disabled some tests in GHC9 because they expect Wingman to build. See Disable hole fit suggestions when running Wingman #1873 and the expectFailIfGhc9 function
  • Pull request in progress: WIP: GHC-9.0 support for hls-tactics-plugin #2202
  • Finally added with Post ghc-9.2.1 config cleanup #2582, follow up of the previous one

Formatters

• hls-floskell-plugin
• hls-ormolu-plugin - Support added with Switch to ghc-lib-parser-9.0.1.xxx tweag/ormolu#688
• hls-brittany-plugin - Blocked upstream by brittany:ghc-lib-parser (Support for ghc-9.0.1 lspitzner/brittany#352)
• hls-fourmolu-plugin - Bump Fourmolu to 0.4 #2254
• hls-stylish-haskell-plugin blocked upstream by
  • stylish-haskell:ghc-lib-parser (Support for ghc-9.0.1 stylish-haskell#378)
  • Add support for aeson >= 2.0 stylish-haskell#387

Build system and CI

• stack-9.0.1.yaml - Disables not-yet-working plugins and fetches upstream patches
• cabal-ghc901.project - Used for disabling the not yet working plugins and fetching upstream patches
• flake.nix - Needs to fetch upstream patches and disable not-yet-working plugins (nix: add support for ghc 9.0.1 #1995)
• .circleci/config.yml
• .github/workflows/test.yml - Uses the custom cabal.project and disables tests for non-working plugins. Needs to be updated when more plugins gain ghc-9.0.1 support
• .github/workflows/build.yml - The release script is not updated to make a ghc-9.0.1 release yet (PR Add ghc-9.0.1 to the build release script #1940)
• mergify.io We should probably make it manditory for PRs to successfully build/test on ghc-9.0.1 as well

Dependencies which needs updates and hackage release

• blaze-textual: Allow build for GHC 9.0 swamp-agr/blaze-textual#14. Released in hackage.
• czipwith: Fix GHC 9 compatibility lspitzner/czipwith#2.
• th-extras: Add support for ghc-9.0.1 mokus0/th-extras#8. Needs hackage release: Upload to Hackage mokus0/th-extras#10
• hie-bios: Add compatibility for GHC 9.0 and 9.2 hie-bios#300 (needs hackage release)
• dependent-sum: Add support for GHC-9.0.1 obsidiansystems/dependent-sum#57. Needs hackage release, see New release with ghc 9 compat obsidiansystems/dependent-sum#65
• ghc-api-compat: Drop ghc-api-compat from dependency closure #2128
• operational (shake-bench dependency): Fix build for GHC 9.0.1 HeinrichApfelmus/operational#26 (needs hackage release Hackage release with 9.0.1 support HeinrichApfelmus/operational#29)
  • Support added with Remove custom version of operational #2249

Dependencies needed to inlcude brittany in hackage for 9.0:

• multistate: Allow base 4.15 lspitzner/multistate#8, finally added with Fix build with GHC 9.2.1 lspitzner/multistate#11
• data-tree-print: Allow base < 4.17 and ghc <= 9.2.1 lspitzner/data-tree-print#3
• butcher: Support for base-4.15 and ghc-9.0.* lspitzner/butcher#8