From c071c02345bc9fd272e215b84aa09b9ab942a7ee Mon Sep 17 00:00:00 2001
From: Ben Sima <ben@bsima.me>
Date: Fri, 14 Nov 2025 22:03:26 -0500
Subject: Fix per-module link: copy .hi files locally instead of using -i paths

GHC --make was treating -i /nix/store/.../hidir paths as compilation targets.
Solution: Copy all .hi files to local directory and use -i. only.

Also make hsGraph optional with 'or null' for backward compatibility with
old bild binaries during bootstrap.

Amp-Thread-ID: https://ampcode.com/threads/T-fe68faaf-1c1d-4c43-a377-1cf5e6cffb3a
Co-authored-by: Amp <amp@ampcode.com>
---
 Omni/Bild/Builder.nix | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

(limited to 'Omni/Bild/Builder.nix')

diff --git a/Omni/Bild/Builder.nix b/Omni/Bild/Builder.nix
index fa732be..6610a27 100644
--- a/Omni/Bild/Builder.nix
+++ b/Omni/Bild/Builder.nix
@@ -116,7 +116,7 @@ with bild; let
       };
 
       haskell =
-        if target.hsGraph == null
+        if (target.hsGraph or null) == null
         then
           # Monolithic build (fallback for TH/cycles)
           stdenv.mkDerivation rec {
@@ -228,14 +228,15 @@ with bild; let
               dontConfigure = true;
               buildPhase = let
                 pkgFlags = lib.strings.concatMapStringsSep " " (p: "-package ${p}") target.langdeps;
-                hiDirs = lib.attrsets.mapAttrsToList (_modName: drv: "${drv}/hidir") modules;
-                iFlags = lib.strings.concatMapStringsSep " " (d: "-i ${d}") hiDirs;
+                copyHiFiles = lib.strings.concatMapStringsSep "\n" (drv: "cp -rL ${drv}/hidir/. . 2>/dev/null || true") (lib.attrsets.attrValues modules);
               in ''
                 set -eux
                 echo "Starting custom link phase with ${builtins.toString (builtins.length objectPaths)} object files"
+                ${copyHiFiles}
+                chmod -R +w . || true
                 ${ghcPkg}/bin/ghc --make \
                   ${target.quapath} \
-                  -i. ${iFlags} \
+                  -i. \
                   ${pkgFlags} \
                   -threaded \
                   -o ${name} \
-- 
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