Fix: write nix-support/propagated-native-build-inputs file

writeShellApplication uses writeTextFile internally, which does NOT
run stdenv.mkDerivation's fixupPhase. Setting propagatedNativeBuildInputs
via overrideAttrs only adds the attribute to the derivation but never
materializes the $out/nix-support/propagated-native-build-inputs file
that setup.sh's findInputs actually reads at runtime.

Without this file, curl was invisible to the shell environment despite
being set as a propagated dep — the wrapper script itself had curl on
its internal PATH, but other programs (like GHC's stage0 cabal) could
not find it.

Fix: explicitly create the nix-support file in postInstall.

Author: angerman

writers.nix

@@ -32,9 +32,20 @@
 #
 # ─── The fix ───────────────────────────────────────────────────────────────────
 #
-# We use overrideAttrs to add propagatedNativeBuildInputs to the wrapper
-# derivation. When stdenv's setup.sh processes the wrapper from
-# nativeBuildInputs, it:
+# We use overrideAttrs to:
+#
+#   1. Set propagatedNativeBuildInputs on the derivation
+#   2. Write the $out/nix-support/propagated-native-build-inputs file
+#
+# Step 2 is critical: writeShellApplication uses writeTextFile internally,
+# which does NOT run stdenv.mkDerivation's fixupPhase. That fixupPhase is
+# what normally materializes the propagatedNativeBuildInputs derivation
+# attribute into the $out/nix-support/propagated-native-build-inputs file
+# that setup.sh's findInputs reads at runtime. Without the file on disk,
+# setting the attribute alone has no effect — setup.sh never sees it.
+#
+# With the file in place, when stdenv's setup.sh processes the wrapper
+# from buildInputs or nativeBuildInputs, it:
 #
 #   1. Adds $wrapper/bin to PATH  (the wrapper itself)
 #   2. Reads $wrapper/nix-support/propagated-native-build-inputs
@@ -64,8 +75,24 @@
 { pkgs }:
 {
   writeShellApplicationWithRuntime = args@{ runtimeInputs ? [], ... }:
+    let
+      allPropagated = runtimeInputs;
+      # Space-separated store paths for the propagation file, matching the
+      # format that stdenv's setup.sh findInputs expects.
+      propagatedPathsStr = builtins.concatStringsSep " "
+        (map (dep: "${dep}") allPropagated);
+    in
     (pkgs.writeShellApplication args).overrideAttrs (old: {
       propagatedNativeBuildInputs =
-        (old.propagatedNativeBuildInputs or []) ++ runtimeInputs;
+        (old.propagatedNativeBuildInputs or []) ++ allPropagated;
+
+      # writeShellApplication (via writeTextFile) does NOT run stdenv's
+      # fixupPhase, so the propagatedNativeBuildInputs attribute is never
+      # materialized into the nix-support/ file that setup.sh reads.
+      # We create it explicitly in postInstall.
+      postInstall = (old.postInstall or "") + ''
+        mkdir -p $out/nix-support
+        echo "${propagatedPathsStr}" > $out/nix-support/propagated-native-build-inputs
+      '';
     });
 }