Use Nixpkgs Wasm GHC

.github/workflows/web-demos.yml

@@ -43,10 +43,8 @@ jobs:
             ~/.npm
             ~/.cargo/registry
             ~/.cargo/git
-            ~/.ghc-wasm/.cabal
             target
-            dist-newstyle
-          key: web-demos-${{ runner.os }}-${{ hashFiles('flake.lock', 'Cargo.lock', 'cabal.project', 'packages/**/*.cabal', 'packages/coln-js-runtime/package-lock.json', 'examples/sync-demo/pnpm-lock.yaml') }}
+          key: web-demos-${{ runner.os }}-${{ hashFiles('flake.lock', 'Cargo.lock', 'packages/coln-js-runtime/package-lock.json', 'examples/sync-demo/pnpm-lock.yaml') }}
           restore-keys: |
             web-demos-${{ runner.os }}-
 
@@ -55,57 +53,60 @@ jobs:
         env:
           VITE_BASE: /sync/
 
-      - name: Build web compiler
-        run: |
-          nix develop --accept-flake-config --command wasm32-wasi-cabal update 'hackage.haskell.org,2026-07-15T17:07:49Z'
-          nix develop --accept-flake-config --command just examples/build-web-compiler
+      # TODO commented out to prevent CI compiling a GHC from source
+      # - name: Build web compiler
+      #   run: |
+      #     nix build --accept-flake-config .#web-compiler
+      #     mkdir -p _build/web
+      #     cp -rL result _build/web/compiler
+      #     chmod -R u+w _build/web/compiler
 
-      - name: Assemble deploy directory
-        run: |
-          cp examples/index.html examples/style.css _build/web/
-          cp -r examples/sync-demo/dist _build/web/sync
+      # - name: Assemble deploy directory
+      #   run: |
+      #     cp examples/index.html examples/style.css _build/web/
+      #     cp -r examples/sync-demo/dist _build/web/sync
 
-      - name: Deploy PR preview to Netlify
-        id: deploy-preview
-        if: github.event_name == 'pull_request' && env.NETLIFY_AUTH_TOKEN != '' && env.NETLIFY_SITE_ID != ''
-        run: |
-          npx --yes netlify-cli@latest deploy \
-            --auth "$NETLIFY_AUTH_TOKEN" \
-            --site "$NETLIFY_SITE_ID" \
-            --dir _build/web \
-            --no-build \
-            --alias "pr-${{ github.event.pull_request.number }}" \
-            --message "PR #${{ github.event.pull_request.number }} web demos" \
-            --json > netlify-deploy.json
+      # - name: Deploy PR preview to Netlify
+      #   id: deploy-preview
+      #   if: github.event_name == 'pull_request' && env.NETLIFY_AUTH_TOKEN != '' && env.NETLIFY_SITE_ID != ''
+      #   run: |
+      #     npx --yes netlify-cli@latest deploy \
+      #       --auth "$NETLIFY_AUTH_TOKEN" \
+      #       --site "$NETLIFY_SITE_ID" \
+      #       --dir _build/web \
+      #       --no-build \
+      #       --alias "pr-${{ github.event.pull_request.number }}" \
+      #       --message "PR #${{ github.event.pull_request.number }} web demos" \
+      #       --json > netlify-deploy.json
 
-          cat netlify-deploy.json
-          deploy_url=$(node -e "const d = require('./netlify-deploy.json'); console.log(d.deploy_ssl_url || d.ssl_url || d.deploy_url || d.url)")
-          echo "deploy-url=$deploy_url" >> "$GITHUB_OUTPUT"
+      #     cat netlify-deploy.json
+      #     deploy_url=$(node -e "const d = require('./netlify-deploy.json'); console.log(d.deploy_ssl_url || d.ssl_url || d.deploy_url || d.url)")
+      #     echo "deploy-url=$deploy_url" >> "$GITHUB_OUTPUT"
 
-      - name: Comment with deploy preview URL
-        if: github.event_name == 'pull_request' && steps.deploy-preview.outputs.deploy-url != ''
-        uses: actions/github-script@v8
-        with:
-          script: |
-            const marker = '<!-- coln-web-demos-deploy-preview -->'
-            const body = `${marker}\nWeb demo preview: ${{ steps.deploy-preview.outputs.deploy-url }}`
-            const { owner, repo } = context.repo
-            const issue_number = context.issue.number
-            const comments = await github.rest.issues.listComments({ owner, repo, issue_number, per_page: 100 })
-            const existing = comments.data.find(comment => comment.body?.includes(marker))
-            if (existing) {
-              await github.rest.issues.updateComment({ owner, repo, comment_id: existing.id, body })
-            } else {
-              await github.rest.issues.createComment({ owner, repo, issue_number, body })
-            }
+      # - name: Comment with deploy preview URL
+      #   if: github.event_name == 'pull_request' && steps.deploy-preview.outputs.deploy-url != ''
+      #   uses: actions/github-script@v8
+      #   with:
+      #     script: |
+      #       const marker = '<!-- coln-web-demos-deploy-preview -->'
+      #       const body = `${marker}\nWeb demo preview: ${{ steps.deploy-preview.outputs.deploy-url }}`
+      #       const { owner, repo } = context.repo
+      #       const issue_number = context.issue.number
+      #       const comments = await github.rest.issues.listComments({ owner, repo, issue_number, per_page: 100 })
+      #       const existing = comments.data.find(comment => comment.body?.includes(marker))
+      #       if (existing) {
+      #         await github.rest.issues.updateComment({ owner, repo, comment_id: existing.id, body })
+      #       } else {
+      #         await github.rest.issues.createComment({ owner, repo, issue_number, body })
+      #       }
 
-      - name: Deploy main to Netlify production
-        if: github.event_name == 'push' && env.NETLIFY_AUTH_TOKEN != '' && env.NETLIFY_SITE_ID != ''
-        run: |
-          npx --yes netlify-cli@latest deploy \
-            --auth "$NETLIFY_AUTH_TOKEN" \
-            --site "$NETLIFY_SITE_ID" \
-            --dir _build/web \
-            --no-build \
-            --prod \
-            --message "web demos ${{ github.sha }}"
+      # - name: Deploy main to Netlify production
+      #   if: github.event_name == 'push' && env.NETLIFY_AUTH_TOKEN != '' && env.NETLIFY_SITE_ID != ''
+      #   run: |
+      #     npx --yes netlify-cli@latest deploy \
+      #       --auth "$NETLIFY_AUTH_TOKEN" \
+      #       --site "$NETLIFY_SITE_ID" \
+      #       --dir _build/web \
+      #       --no-build \
+      #       --prod \
+      #       --message "web demos ${{ github.sha }}"

cabal.project

@@ -18,6 +18,9 @@ jobs: $ncpus
 semaphore: true
 tests: True
 
+if os(wasi)
+  shared: True
+
 constraints:
   -- Cabal otherwise sometimes picks bad build plans due to faulty metadata in older versions of these libs:
   -- https://github.com/haskell/lsp/issues/641

flake.nix

@@ -1,9 +1,8 @@
 {
   inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixos-26.05";
+    nixpkgs.url = "github:georgefst/nixpkgs/ghc-wasm";
     flake-utils.url = "github:numtide/flake-utils";
     rust-overlay.url = "github:oxalica/rust-overlay";
-    ghc-wasm-meta.url = "gitlab:haskell-wasm/ghc-wasm-meta?host=gitlab.haskell.org";
   };
   outputs =
     inputs@{
@@ -135,6 +134,29 @@
             '';
           };
 
+          # TODO find some way to DRY this with `just examples/build-web-compiler`
+          # TODO do the combined web-demo build in Nix, removing logic from YAML
+          web-compiler = pkgs.runCommand "coln-web-compiler"
+            {
+              nativeBuildInputs = [
+                pkgs.nodejs
+                pkgs.jq
+              ];
+            }
+            ''
+              dist=$out/dist
+              mkdir -p $dist
+              cp ${wasmColnPackages.coln-compiler-wasm}/bin/coln-compiler-wasm* $dist/coln.wasm
+              libdir=$(${wasmHaskellPackages.ghc}/bin/${wasmHaskellPackages.ghc.targetPrefix}ghc --print-libdir)
+              node "$libdir/post-link.mjs" --input $dist/coln.wasm --output $dist/ghc_wasm_jsffi.js
+              cp ${./packages/coln-compiler-wasm/loadHaskellWasm.js} $dist/loadHaskellWasm.js
+              cp ${./examples/compiler-demo/index.html} $out/index.html
+              cp ${./examples/style.css} $out/style.css
+              mkdir -p $out/examples
+              cp ${./packages/coln-compiler/test/golden}/*.coln $out/examples/
+              ls -1 $out/examples/*.coln | xargs -n1 basename | jq -nR '[inputs]' > $out/examples/index.json
+            '';
+
           format-hs = nuShellCheck [pkgs.fourmolu] ./nix/checks/format-hs.nu;
           format-cabal = nuShellCheck [pkgs.haskellPackages.cabal-gild] ./nix/checks/format-cabal.nu;
 
@@ -189,7 +211,30 @@
 
 
         inherit (packages) forester coln-manual-dev;
-        haskell-wasm = inputs.ghc-wasm-meta.packages.${system};
+        # TODO DRY with native builds
+        wasmHaskellPackages = pkgs.pkgsCross.wasi32.haskell.packages.ghc9141.override {
+          overrides = _: prev: {
+            # mirrors cabal.project
+            # TODO these are actually about GHC 9.14 compatibility rather than Wasm
+            ordered-containers = pkgs.haskell.lib.doJailbreak prev.ordered-containers;
+            prettyprinter-lucid = pkgs.haskell.lib.doJailbreak prev.prettyprinter-lucid;
+          };
+        };
+        wasmColnPackages = rec {
+          diagnostician = wasmHaskellPackages.callPackage ./packages/diagnostician { };
+          diagnostician-html = wasmHaskellPackages.callPackage ./packages/diagnostician-html {
+            inherit diagnostician;
+          };
+          fnotation = wasmHaskellPackages.callPackage ./packages/fnotation {
+            inherit diagnostician;
+          };
+          coln-compiler = wasmHaskellPackages.callPackage ./packages/coln-compiler {
+            inherit diagnostician fnotation;
+          };
+          coln-compiler-wasm = wasmHaskellPackages.callPackage ./packages/coln-compiler-wasm {
+            inherit coln-compiler diagnostician diagnostician-html fnotation;
+          };
+        };
         lsTsDir = ./packages/coln-ls/client;
         lsClientNpmDeps = pkgs.importNpmLock {
           npmRoot = lsTsDir;
@@ -221,8 +266,10 @@
             forester
             fourmolu
             esbuild
-            haskell-wasm.wasm32-wasi-ghc-9_14
-            haskell-wasm.wasm32-wasi-cabal-9_14
+            wasmHaskellPackages.ghc
+            (pkgs.writeShellScriptBin "wasm32-unknown-wasi-cabal" ''
+              exec ${pkgs.cabal-install}/bin/cabal --with-compiler=${wasmHaskellPackages.ghc.unprefixed}/bin/ghc "$@"
+            '')
             haskell.compiler.ghc912
             haskell.packages.ghc912.haskell-language-server
             haskellPackages.cabal-gild

packages/coln-compiler-wasm/default.nix

@@ -0,0 +1,17 @@
+{ mkDerivation, aeson, base, coln-compiler, containers
+, diagnostician, diagnostician-html, fnotation, ghc-experimental
+, lib, lucid, ordered-containers, prettyprinter, text
+}:
+mkDerivation {
+  pname = "coln-compiler-wasm";
+  version = "0.1";
+  src = ./.;
+  isLibrary = false;
+  isExecutable = true;
+  executableHaskellDepends = [
+    aeson base coln-compiler containers diagnostician
+    diagnostician-html fnotation ghc-experimental lucid
+    ordered-containers prettyprinter text
+  ];
+  license = "(Apache-2.0 OR MIT)";
+}

packages/coln-compiler-wasm/justfile

@@ -4,8 +4,8 @@ build:
     #!/usr/bin/env bash
     set -euxo pipefail
     mkdir -p {{ dist_dir }}
-    wasm32-wasi-cabal build coln-compiler-wasm
-    cp "$(wasm32-wasi-cabal list-bin coln-compiler-wasm)" {{ dist_dir }}/coln.wasm
-    libdir="$(wasm32-wasi-ghc --print-libdir)"
+    wasm32-unknown-wasi-cabal build coln-compiler-wasm
+    cp "$(wasm32-unknown-wasi-cabal list-bin coln-compiler-wasm)" {{ dist_dir }}/coln.wasm
+    libdir="$(wasm32-unknown-wasi-ghc --print-libdir)"
     "$libdir/post-link.mjs" --input {{ dist_dir }}/coln.wasm --output {{ dist_dir }}/ghc_wasm_jsffi.js
     cp loadHaskellWasm.js {{ dist_dir }}/loadHaskellWasm.js