Add pnpm installation test

Author: cknitt

.github/workflows/ci.yml

@@ -573,6 +573,36 @@ jobs:
         shell: bash
         working-directory: ${{ steps.tmp-dir.outputs.path }}
 
+      - name: Install pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - name: Make test directory (pnpm)
+        id: tmp-dir-pnpm
+        shell: bash
+        run: |
+          if [[ "$RUNNER_OS" == "Windows" ]]; then
+            dir=$(powershell -Command "[System.IO.Path]::GetTempPath() + [System.Guid]::NewGuid().ToString()" | tr -d '\r')
+            mkdir -p "$dir"
+          else
+            dir=$(mktemp -d)
+          fi
+          echo "path=$dir" >> "$GITHUB_OUTPUT"
+          cp -r tests/package_tests/installation_test/* "$dir"
+
+      - name: Install ReScript package (pnpm)
+        run: |
+          COMMIT_SHA="${{ github.event.pull_request.head.sha || github.sha }}"
+          pnpm i "https://pkg.pr.new/rescript-lang/rescript@${COMMIT_SHA::7}"
+        shell: bash
+        working-directory: ${{ steps.tmp-dir-pnpm.outputs.path }}
+
+      - name: Test installation (pnpm)
+        run: pnpm rescript -h && pnpm rescript legacy build && cat src/Test.res.js
+        shell: bash
+        working-directory: ${{ steps.tmp-dir-pnpm.outputs.path }}
+
       - name: Install ReScript package in rewatch/testrepo
         run: |
           COMMIT_SHA="${{ github.event.pull_request.head.sha || github.sha }}"