Skip already published npm versions

.github/workflows/publish.yml

@@ -37,7 +37,22 @@ jobs:
       - name: Typecheck
         run: pnpm typecheck
 
+      - name: Check published version
+        id: published
+        shell: bash
+        run: |
+          set -euo pipefail
+          name="$(node -p "require('./package.json').name")"
+          version="$(node -p "require('./package.json').version")"
+          if npm view "${name}@${version}" version >/dev/null 2>&1; then
+            echo "exists=true" >> "$GITHUB_OUTPUT"
+            echo "${name}@${version} is already published; skipping npm publish."
+          else
+            echo "exists=false" >> "$GITHUB_OUTPUT"
+          fi
+
       - name: Publish
+        if: steps.published.outputs.exists != 'true'
         run: npm publish --provenance
         env:
           NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}