[cli][node] Re-apply @TooTallNate's vc dev updates (#4254)

This reverts commit 099bc6dbf6 (#4231).

packages/now-node/src/dev-server.ts

@@ -0,0 +1,75 @@
+import { register } from 'ts-node';
+
+// Use the project's version of TypeScript if available,
+// otherwise fall back to using the copy that `@now/node` uses.
+let compiler: string;
+try {
+  compiler = require.resolve('typescript', {
+    paths: [process.cwd(), __dirname],
+  });
+} catch (e) {
+  compiler = 'typescript';
+}
+
+register({
+  compiler,
+  compilerOptions: {
+    allowJs: true,
+    esModuleInterop: true,
+    jsx: 'react',
+  },
+  transpileOnly: true,
+});
+
+import http from 'http';
+import path from 'path';
+import { createServerWithHelpers } from './helpers';
+
+function listen(
+  server: http.Server,
+  port: number,
+  host: string
+): Promise<void> {
+  return new Promise(resolve => {
+    server.listen(port, host, () => {
+      resolve();
+    });
+  });
+}
+
+async function main() {
+  const entrypoint = process.env.NOW_DEV_ENTRYPOINT;
+  delete process.env.NOW_DEV_ENTRYPOINT;
+
+  if (!entrypoint) {
+    throw new Error('`NOW_DEV_ENTRYPOINT` must be defined');
+  }
+
+  const config = JSON.parse(process.env.NOW_DEV_CONFIG || '{}');
+  delete process.env.NOW_DEV_CONFIG;
+
+  const shouldAddHelpers = !(
+    config.helpers === false || process.env.NODEJS_HELPERS === '0'
+  );
+
+  const entrypointPath = path.join(process.cwd(), entrypoint);
+  const handler = await import(entrypointPath);
+
+  const server = shouldAddHelpers
+    ? createServerWithHelpers(handler.default)
+    : http.createServer(handler.default);
+
+  await listen(server, 0, '127.0.0.1');
+
+  const address = server.address();
+  if (typeof process.send === 'function') {
+    process.send(address);
+  } else {
+    console.log('Dev server listening:', address);
+  }
+}
+
+main().catch(err => {
+  console.error(err);
+  process.exit(1);
+});