CI: build every template for the browser with emcc

.github/workflows/release.yml

@@ -41,6 +41,33 @@ jobs:
           name: miso-${{ matrix.system }}
           path: result/*
 
+  # Every template built for the browser with emcc, as a new user would:
+  # the smoke test builds native programs only (scripts/template-test.sh).
+  # emcc comes from the nixpkgs miso is built with (flake.lock), so this
+  # builds with the emscripten miso is tested against.
+  templates:
+    needs: build
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { system: x86_64-linux,   runner: ubuntu-latest }
+          - { system: aarch64-darwin, runner: macos-latest }
+    runs-on: ${{ matrix.runner }}
+    steps:
+      - uses: actions/checkout@v5
+      - uses: cachix/install-nix-action@v31
+      - uses: actions/download-artifact@v5
+        with:
+          name: miso-${{ matrix.system }}
+          path: dist
+      - name: Build the templates for the browser
+        run: |
+          rev=$(jq -r '.nodes[.nodes.miso.inputs.nixpkgs].locked.rev' flake.lock)
+          echo "emscripten from nixpkgs $rev"
+          nix shell "github:NixOS/nixpkgs/$rev#emscripten" \
+            --command scripts/template-test.sh dist/miso-${{ matrix.system }}.tar.gz
+
   build-intel-mac:
     # GitHub retired the macos-13 image (jobs wait for it forever);
     # macos-15-intel is the free Intel runner.
@@ -88,7 +115,7 @@ jobs:
 
   release:
     if: startsWith(github.ref, 'refs/tags/v')
-    needs: [build, build-intel-mac, build-windows]
+    needs: [build, templates, build-intel-mac, build-windows]
     runs-on: ubuntu-latest
     permissions:
       contents: write

scripts/template-test.sh

@@ -0,0 +1,47 @@
+#!/bin/sh
+# Build every template for the browser with emcc, as a new user would:
+# miso new, then miso build for target: browser (WebAssembly) and
+# browser_js (JavaScript), and the counter as miso dev builds it (miso build
+# --dev: combinators, run by a runtime built with emcc).  The smoke test
+# builds native programs only, so without this a release could ship
+# templates that do not build for the browser.
+#
+#   scripts/template-test.sh miso-SYSTEM.tar.gz      (emcc on the PATH)
+set -eu
+tarball=$1
+tmp=$(mktemp -d)
+tar -C "$tmp" -xzf "$tarball"
+export MISO_HOME=$tmp/home PATH="$(ls -d "$tmp"/miso-*)/bin:$PATH"
+miso version
+emcc --version | head -1
+cd "$tmp"
+
+fail() { echo "template test: $1" >&2; [ -f "${2:-}" ] && cat "$2" >&2; exit 1; }
+
+for template in $(miso templates | awk '$1 != "==>" { print $1 }'); do
+  for target in browser browser_js; do
+    name=$template-$(echo "$target" | tr _ -)
+    miso new "$name" --template "$template" > /dev/null
+    (
+      cd "$name"
+      sed "s/^target: browser\$/target: $target/" miso.yml > miso.yml.new
+      mv miso.yml.new miso.yml
+      grep -q "^target: $target\$" miso.yml || fail "$name: miso.yml has no target: $target" miso.yml
+      miso build > build.log 2>&1 || fail "$name: miso build failed" build.log
+      [ -s public/index.js ] || fail "$name: miso build made no public/index.js" build.log
+      [ -s public/index.html ] || fail "$name: miso build made no public/index.html" build.log
+      echo "template test: $name ok ($(du -sh public | cut -f1))"
+    )
+  done
+done
+
+# miso dev's build: the program as combinators, and the runtime that runs them
+miso new counter-dev > /dev/null
+(
+  cd counter-dev
+  miso build --dev counter-dev > build.log 2>&1 || fail "counter-dev: miso build --dev failed" build.log
+  [ -s public/app.comb ] || fail "counter-dev: miso build --dev made no public/app.comb" build.log
+  [ -s public/index.js ] || fail "counter-dev: miso build --dev made no public/index.js" build.log
+  echo "template test: counter-dev ok (miso build --dev)"
+)
+echo "template test: ok"