Build fails on WASM

[brandonchinn178]

Got a failure when building ghc-lib-parser with GHC WASM. Not sure if it's a ghc-lib-parser issue or a GHC WASM issue, but I figured I'd start here

https://github.com/fourmolu/fourmolu/actions/runs/17982289343/job/51151331706?pr=490

Failed to build ghc-lib-parser-9.12.2.20250421.

 compiler/GHC/Tc/Errors/Ppr.hs:44:1: error: [GHC-61948]
    Could not find module ‘GHC.Internal.TH.Ppr’.
    Perhaps you meant
      GHC.Internal.TH.Lib (from ghc-internal-9.1202.0)
      GHC.Internal.Ptr (from ghc-internal-9.1202.0)
      GHC.Internal.TH.Lift (from ghc-internal-9.1202.0)
    Use -v to see a list of the files searched for.
   |
44 | import qualified GHC.Internal.TH.Ppr as TH
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[shayne-fletcher]

what's the build compiler version? i see

    if impl(ghc < 9.12.1)
      hs-source-dirs:
        libraries/ghc-internal/src
        libraries/ghc-boot-th-internal
      exposed-modules:
            GHC.Internal.ForeignSrcLang
            GHC.Internal.LanguageExtensions
            GHC.Internal.Lexeme
            GHC.Internal.TH.Syntax
            GHC.Internal.TH.Ppr
            GHC.Internal.TH.PprLib
            GHC.Internal.TH.Lib.Map

in that cabal file. you might try doing surgery on it to see if we can wriggle past this problem?do let us know!

[brandonchinn178]

Oh is that new? This is with ghc-9.12.2.20250922. It passed on an earlier run that used ghc-9.12.2.20250828.

[TerrorJack]

that's a regression in upstream 9.12.3-rc1; the wasm releases are always rebased on upstream release branches. also see https://gitlab.haskell.org/ghc/head.hackage/-/blob/master/patches/ghc-lib-parser-9.12.2.20250421.patch#L31

[brandonchinn178]

@TerrorJack Thanks, how do I apply that patch in my build?

[TerrorJack]

a source-repository-package for the time being; though maybe doing an upstream hackage release on the 9.12 branch would solve this?

[brandonchinn178]

Pinning GHC WASM seems to have worked for now: fourmolu/fourmolu@f2787f8