WASM hello world

shell.nix

@@ -1,4 +1,5 @@
 {
+  callPackage,
   haskellPackages,
   haskell,
   zlib,
@@ -7,40 +8,72 @@
   wasm32-wasi-ghc,
   writeShellApplication,
   nodejs,
+  pkg-config,
   python3,
+  fetchFromGitHub,
 }:
-haskellPackages.developPackage {
-  name = "numbersquare";
-  root = ./.;
-  modifier =
-    let
-      addBuildTools =
-        drv:
-        haskell.lib.addBuildTools drv (
-          [
-            watchexec
-            wasm32-wasi-cabal
-            wasm32-wasi-ghc
-            nodejs
-            (writeShellApplication {
-              name = "dev-server";
-              text = ''
-                python -m http.server -d ./out
-              '';
-              runtimeInputs = [ python3 ];
-            })
-          ]
-          ++ (with haskellPackages; [
-            fourmolu
-            haskell-language-server
-            cabal-install
-            hpack
-            ghcid
-            cabal-fmt
-            hoogle
-          ])
-        );
-      addExtraLibraries = drv: haskell.lib.addExtraLibraries drv [ zlib ];
-    in
-    drv: addExtraLibraries (addBuildTools drv);
-}
+let
+  # TODO: this information is duplicated at the bottom. need to fix that.
+  ghc-wasm-compat-rev = "ef21ada9436046c7b118314d0c73752253ec58e1";
+  ghc-wasm-compat-src = fetchFromGitHub {
+    owner = "konn";
+    repo = "ghc-wasm-earthly";
+    rev = ghc-wasm-compat-rev;
+    hash = "sha256-oUf7HFLNxBZ/roFRe5q7Sz0D0ZRygu8prxEYoYuhSU8=";
+  };
+in
+let
+  shell = haskellPackages.developPackage {
+    name = "numbersquare";
+    root = ./.;
+    overrides = _: _: {
+      ghc-wasm-compat =
+        haskellPackages.callCabal2nix "ghc-wasm-compat" "${ghc-wasm-compat-src}/ghc-wasm-compat"
+          { };
+    };
+    modifier =
+      let
+        addBuildTools =
+          drv:
+          haskell.lib.addBuildTools drv (
+            [
+              watchexec
+              wasm32-wasi-cabal
+              wasm32-wasi-ghc
+              nodejs
+              pkg-config
+              (writeShellApplication {
+                name = "dev-server";
+                text = ''
+                  python -m http.server -d ./out
+                '';
+                runtimeInputs = [ python3 ];
+              })
+            ]
+            ++ (with haskellPackages; [
+              fourmolu
+              happy
+              haskell-language-server
+              cabal-install
+              hpack
+              ghcid
+              cabal-fmt
+              hoogle
+            ])
+          );
+        addExtraLibraries = drv: haskell.lib.addExtraLibraries drv [ zlib ];
+      in
+      drv: addExtraLibraries (addBuildTools drv);
+  };
+in
+shell.overrideAttrs (old: {
+  shellHook = (old.shellHook or "") + ''
+    cat > cabal.project.local <<EOF
+    source-repository-package
+      type: git
+      location: https://github.com/konn/ghc-wasm-earthly
+      tag: ${ghc-wasm-compat-rev}
+      subdir: ghc-wasm-compat
+    EOF
+  '';
+})