Add Deno Runtime Support

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Add Deno Runtime Support

Overview

Add dual runtime support to hello-world-web, allowing the application to run on both Node.js 22 and Deno 2.x with identical functionality.

Motivation

• Learning: Explore Deno 2.x's Node.js compatibility in a real-world application
• Performance: Compare runtime performance between Node.js and Deno
• Modern tooling: Leverage Deno's built-in TypeScript, linting, and formatting
• Flexibility: Maintain deployment options across runtimes

Implementation Status

✅ Phase 1-3: Completed

• Create deno.json configuration
• Verify Express.js compatibility via npm: specifiers
• Add pnpm start:deno and pnpm dev:deno scripts
• Create runtime detection helper (packages/app/src/runtime.ts)
• Verify all routes and SSR work on Deno

🚧 Phase 5-6: In Progress (PR #TBD)

• Add Deno matrix to test.yml (lint + build)
• Add Deno matrix to bdd-tests.yml (E2E tests)
• Create optimized Dockerfile.deno (multi-stage, static compilation if possible)
• Add Deno Docker E2E test workflow
• Deploy Deno version to Cloud Run (dev-deno.hello.kiste.li)
• Update documentation

Technical Details

No Code Changes Required!
The codebase was already Deno-compatible due to:

• Pure ESM (`"type": "module"`)
• `node:` prefixes on built-in imports
• No `require()` calls
• Modern TypeScript

Works Out of the Box:

• ✅ Express 5.1 via `npm:express@^5.1.0`
• ✅ All middleware (cookie-parser, morgan, dotenv)
• ✅ @lit-labs/ssr (SSR + hydration)
• ✅ Static file serving
• ✅ All routes

Testing

• Local: `pnpm start:deno` or `deno task start`
• CI: Matrix strategy tests both runtimes in parallel

Deployment

• Node: `hello.kiste.li` (existing, unchanged)
• Deno: `dev-deno.hello.kiste.li` (new, separate service)

Design Document

See docs/plans/2025-11-30-deno-runtime-support-design.md for complete design.

Related

• Branch: `deno`
• PR: #TBD