From 622489c23a691e1bc2f23736af1a97b1007d4e70 Mon Sep 17 00:00:00 2001
From: Ross Smyth <18294397+RossSmyth@users.noreply.github.com>
Date: Fri, 17 Oct 2025 16:35:07 -0400
Subject: [PATCH] idris2: Make prelude library build helper

---
 pkgs/by-name/id/idris2/mkPrelude.nix | 39 ++++++++++++++++++++++++++++
 pkgs/by-name/id/idris2/package.nix   |  2 ++
 2 files changed, 41 insertions(+)
 create mode 100644 pkgs/by-name/id/idris2/mkPrelude.nix

diff --git a/pkgs/by-name/id/idris2/mkPrelude.nix b/pkgs/by-name/id/idris2/mkPrelude.nix
new file mode 100644
index 000000000000..90659c8c4fe6
--- /dev/null
+++ b/pkgs/by-name/id/idris2/mkPrelude.nix
@@ -0,0 +1,39 @@
+{
+  lib,
+  stdenvNoCC,
+  idris2-src,
+  idris2-version,
+  idris2-unwrapped,
+}:
+lib.extendMkDerivation {
+  constructDrv = stdenvNoCC.mkDerivation;
+
+  excludeDrvArgNames = [
+    "dependencies"
+  ];
+
+  extendDrvArgs =
+    finalAttrs:
+    {
+      name,
+      dependencies ? [ ],
+    }:
+    {
+      pname = name;
+      version = idris2-version;
+      src = idris2-src;
+      strictDeps = true;
+
+      makeFlags = "IDRIS2=${lib.getExe idris2-unwrapped}";
+
+      enableParallelBuilding = true;
+      preBuild = ''
+        cd libs/${name}
+      '';
+
+      env = {
+        IDRIS2_PREFIX = placeholder "out";
+        IDRIS2_PACKAGE_PATH = lib.makeSearchPath "idris2-${idris2-version}" dependencies;
+      };
+    };
+}
diff --git a/pkgs/by-name/id/idris2/package.nix b/pkgs/by-name/id/idris2/package.nix
index 694160d9d5c1..77adf53b0c34 100644
--- a/pkgs/by-name/id/idris2/package.nix
+++ b/pkgs/by-name/id/idris2/package.nix
@@ -18,6 +18,8 @@ let
         rev = "v${self.idris2-version}";
         hash = "sha256-VwveX3fZfrxEsytpbOc5Tm6rySpLFhTt5132J6rmrmM=";
       };
+      # Prelude libraries
+      mkPrelude = callPackage ./mkPrelude.nix { }; # Build helper
 
       libidris2_support = callPackage ./libidris2_support.nix { };
       idris2-unwrapped = callPackage ./unwrapped.nix { };