haskell-language-server: this operation requires -fexternal-interpreter

[hamishmack]

This error seems to happen when using reinstallableLibGhc = true with haskell-language-server (which is now the default). We should try to fix the reinstallableLibGhc, but of now anyone seeing this error can add a modules = [{ reinstallableLibGhc = false; }];, for instance changing:

tools = {
  haskell-language-server = {};
};

to

tools = {
  haskell-language-server = { modules = [{ reinstallableLibGhc = false; }]; };
};

[hamishmack]

One way to reproduce this is:

git clone [email protected]:/input-output-hk/cardano-wallet
cd cardano-wallet
git checkout f1c2697b4
direnv allow
haskell-language-server lib/core/src/Cardano/Wallet.hs

[ocharles]

To others on GHC 9+, the fix is more than just reinstallableLibGhc = false;, you'll also need to set:

  nonReinstallablePkgs = [
    "rts"
    "ghc-heap"
    "ghc-prim"
    "integer-gmp"
    "integer-simple"
    "base"
    "deepseq"
    "array"
    "ghc-boot-th"
    "pretty"
    "template-haskell"
    "ghcjs-prim"
    "ghcjs-th"
    "ghc-bignum"
    "exceptions"
    "stm"
    "ghc-boot"
    "ghc"
    "Cabal"
    "Win32"
    "array"
    "binary"
    "bytestring"
    "containers"
    "directory"
    "filepath"
    "ghc-boot"
    "ghc-compact"
    "ghc-prim"
    "hpc"
    "mtl"
    "parsec"
    "process"
    "text"
    "time"
    "transformers"
    "unix"
    "xhtml"
    "terminfo"
  ];