Propagate writeShellApplication runtimeInputs via propagatedNativeBuildInputs

cross-js.nix

@@ -12,9 +12,12 @@ let tool-version-map = (import ./tool-map.nix) self;
     # add a trace helper. This will trace a message about disabling a component despite requesting it, if it's not supported in that compiler.
     compiler-not-in = compiler-list: name: (if __elem compiler-nix-name compiler-list then __trace "No ${name}. Not yet compatible with ${compiler-nix-name}" false else true);
 
+    writers = import ./writers.nix { inherit pkgs; };
+
     # * wrapped tools:
-    # A cabal-install wrapper that sets the appropriate static flags
-    wrapped-cabal = pkgs.writeShellApplication {
+    # A cabal-install wrapper that sets the appropriate static flags.
+    # See writers.nix for why writeShellApplicationWithRuntime is needed.
+    wrapped-cabal = writers.writeShellApplicationWithRuntime {
         name = "cabal";
         runtimeInputs = [ cabal-install pkgs.curl ];
         text = with pkgs; ''
@@ -86,7 +89,6 @@ pkgs.mkShell ({
     buildInputs = [];
 
     nativeBuildInputs = [ wrapped-hsc2hs wrapped-cabal compiler ] ++ (with pkgs; [
-        curl
         nodejs # helpful to evaluate output on the commandline.
         cabal-install
         (pkgs.pkg-config or pkgconfig)

cross-windows.nix

@@ -72,9 +72,14 @@ let tool-version-map = (import ./tool-map.nix) self;
         kill $RISERV_PID
       '';
 
+    # Use pkgsBuildBuild for the writers helper — cross-windows wrappers must be
+    # build-platform executables, not target-platform (which is Windows).
+    writers = import ./writers.nix { pkgs = pkgs.pkgsBuildBuild; };
+
     # * wrapped tools:
-    # A cabal-install wrapper that sets the appropriate static flags
-    wrapped-cabal = pkgs.pkgsBuildBuild.writeShellApplication {
+    # A cabal-install wrapper that sets the appropriate static flags.
+    # See writers.nix for why writeShellApplicationWithRuntime is needed.
+    wrapped-cabal = writers.writeShellApplicationWithRuntime {
         name = "cabal";
         runtimeInputs = [ cabal-install curl ];
         text = ''

dynamic.nix

@@ -13,6 +13,8 @@ let tool-version-map = (import ./tool-map.nix) self;
     # add a trace helper. This will trace a message about disabling a component despite requesting it, if it's not supported in that compiler.
     compiler-not-in = compiler-list: name: (if __elem compiler-nix-name compiler-list then __trace "No ${name}. Not yet compatible with ${compiler-nix-name}" false else true);
 
+    writers = import ./writers.nix { inherit pkgs; };
+
     # * wrapped tools:
     # fixup-nix-deps allows us to drop dylibs from macOS executables that can be
     # linked directly.
@@ -40,7 +42,9 @@ let tool-version-map = (import ./tool-map.nix) self;
     # have in the static configuration, and we may imagine needing to inject
     # some flags into cabal (temporarily), hence we'll keep this functionality
     # here.
-    wrapped-cabal = pkgs.writeShellApplication {
+    #
+    # See writers.nix for why writeShellApplicationWithRuntime is needed.
+    wrapped-cabal = writers.writeShellApplicationWithRuntime {
         name = "cabal";
         runtimeInputs = [ cabal-install pkgs.curl ];
         text = ''
@@ -109,7 +113,6 @@ pkgs.mkShell {
         stdenv.cc.cc.lib
       ]
       ++ (with pkgs; [
-        curl
         openssl
         pcre
         pkg-config

static.nix

@@ -10,6 +10,8 @@ let tool-version-map = (import ./tool-map.nix) self;
     # add a trace helper. This will trace a message about disabling a component despite requesting it, if it's not supported in that compiler.
     compiler-not-in = compiler-list: name: (if __elem compiler-nix-name compiler-list then __trace "No ${name}. Not yet compatible with ${compiler-nix-name}" false else true);
 
+    writers = import ./writers.nix { inherit pkgs; };
+
     # * wrapped tools:
     # fixup-nix-deps allows us to drop dylibs from macOS executables that can be
     # linked directly.
@@ -29,8 +31,9 @@ let tool-version-map = (import ./tool-map.nix) self;
         done
       '';
     };
-    # A cabal-install wrapper that sets the appropriate static flags
-    wrapped-cabal = pkgs.writeShellApplication {
+    # A cabal-install wrapper that sets the appropriate static flags.
+    # See writers.nix for why writeShellApplicationWithRuntime is needed.
+    wrapped-cabal = writers.writeShellApplicationWithRuntime {
         name = "cabal";
         runtimeInputs = [ cabal-install pkgs.curl ];
         text = with pkgs; ''
@@ -148,7 +151,6 @@ pkgs.mkShell (rec {
         # products to be static.
         (compiler.override { enableShared = true; })
     ] ++ (with pkgs; [
-        curl
         (pkgs.pkg-config or pkgconfig)
         stdenv.cc.cc.lib ]) ++ (with pkgs.buildPackages; [
     ])

writers.nix

@@ -0,0 +1,71 @@
+# writeShellApplicationWithRuntime — a drop-in replacement for writeShellApplication
+# that also propagates runtimeInputs to dependent environments.
+#
+# ─── The problem ───────────────────────────────────────────────────────────────
+#
+# nixpkgs' writeShellApplication accepts a `runtimeInputs` parameter and
+# compiles it into the wrapper script as:
+#
+#   export PATH="${lib.makeBinPath runtimeInputs}:$PATH"
+#
+# This means the runtime inputs are only on PATH **inside the wrapper script
+# itself**. They are NOT exposed as derivation attributes — not in
+# propagatedNativeBuildInputs, not in passthru, nowhere.
+#
+# When a wrapper built this way is placed into a mkShell's buildInputs or
+# nativeBuildInputs, `nix develop` reconstructs the environment by evaluating
+# the shell derivation and walking all inputs. The Nix C++ evaluator (used by
+# `nix develop` / `nix print-dev-env`) follows the full derivation closure, so
+# it discovers everything transitively — including the runtimeInputs baked into
+# wrapper scripts.
+#
+# However, devx generates `-env` container scripts at **evaluation time** using
+# devShellTools. These scripts export raw derivation attributes and then
+# `source "$stdenv/setup"` to reconstruct the environment. stdenv's setup.sh
+# walks dependencies via the `findInputs` function (stdenv/setup lines 715-806),
+# which reads `$pkg/nix-support/propagated-*` metadata files to discover
+# transitive inputs. It does NOT look inside wrapper scripts.
+#
+# The result: any program in the -env container that is NOT the wrapper itself
+# (e.g. GHC's stage0 bootstrap cabal, or any script that shells out to curl)
+# cannot find the wrapper's runtimeInputs on PATH.
+#
+# ─── The fix ───────────────────────────────────────────────────────────────────
+#
+# We use overrideAttrs to add propagatedNativeBuildInputs to the wrapper
+# derivation. When stdenv's setup.sh processes the wrapper from
+# nativeBuildInputs, it:
+#
+#   1. Adds $wrapper/bin to PATH  (the wrapper itself)
+#   2. Reads $wrapper/nix-support/propagated-native-build-inputs
+#   3. Recursively calls findInputs on each propagated input
+#   4. Adds $curl/bin, $cabal-install/bin, etc. to PATH
+#
+# This makes runtimeInputs visible to the ENTIRE shell environment, not just
+# inside the wrapper. The wrapper still has its own inline PATH injection
+# (via writeShellApplication), so it works in both contexts.
+#
+# ─── Why not upstream? ─────────────────────────────────────────────────────────
+#
+# Ideally, nixpkgs' writeShellApplication would set propagatedNativeBuildInputs
+# from runtimeInputs by default. Until that happens, this wrapper bridges
+# the gap. If upstream adopts this, this file becomes a no-op passthrough
+# and can be removed.
+#
+# ─── Usage ─────────────────────────────────────────────────────────────────────
+#
+#   let writers = import ./writers.nix { inherit pkgs; };
+#   in writers.writeShellApplicationWithRuntime {
+#     name = "cabal";
+#     runtimeInputs = [ cabal-install pkgs.curl ];
+#     text = ''...'';
+#   }
+#
+{ pkgs }:
+{
+  writeShellApplicationWithRuntime = args@{ runtimeInputs ? [], ... }:
+    (pkgs.writeShellApplication args).overrideAttrs (old: {
+      propagatedNativeBuildInputs =
+        (old.propagatedNativeBuildInputs or []) ++ runtimeInputs;
+    });
+}