fix(socket-handler): Fix socket handler race condition by differentiating between async and sync handlers. Now, async socket handlers complete their setup before initial data is emitted, ensuring that no data is lost. Documentation and tests have been updated to reflect this change.

test/test.socket-handler-race.ts

@@ -0,0 +1,83 @@
+import { expect, tap } from '@git.zone/tstest/tapbundle';
+import * as net from 'net';
+import { SmartProxy } from '../ts/index.js';
+
+tap.test('should handle async handler that sets up listeners after delay', async () => {
+  const proxy = new SmartProxy({
+    routes: [{
+      name: 'delayed-setup-handler',
+      match: { ports: 7777 },
+      action: {
+        type: 'socket-handler',
+        socketHandler: async (socket) => {
+          // Simulate async work BEFORE setting up listeners
+          await new Promise(resolve => setTimeout(resolve, 50));
+          
+          // Now set up the listener - with the race condition, this would miss initial data
+          socket.on('data', (data) => {
+            const message = data.toString().trim();
+            socket.write(`RECEIVED: ${message}\n`);
+            if (message === 'close') {
+              socket.end();
+            }
+          });
+          
+          // Send ready message
+          socket.write('HANDLER READY\n');
+        }
+      }
+    }],
+    enableDetailedLogging: false
+  });
+  
+  await proxy.start();
+  
+  // Test connection
+  const client = new net.Socket();
+  let response = '';
+  
+  client.on('data', (data) => {
+    response += data.toString();
+  });
+  
+  await new Promise<void>((resolve, reject) => {
+    client.connect(7777, 'localhost', () => {
+      // Send initial data immediately - this tests the race condition
+      client.write('initial-message\n');
+      resolve();
+    });
+    client.on('error', reject);
+  });
+  
+  // Wait for handler setup and initial data processing
+  await new Promise(resolve => setTimeout(resolve, 150));
+  
+  // Send another message to verify handler is working
+  client.write('test-message\n');
+  
+  // Wait for response
+  await new Promise(resolve => setTimeout(resolve, 50));
+  
+  // Send close command
+  client.write('close\n');
+  
+  // Wait for connection to close
+  await new Promise(resolve => {
+    client.on('close', () => resolve(undefined));
+  });
+  
+  console.log('Response:', response);
+  
+  // Should have received the ready message
+  expect(response).toContain('HANDLER READY');
+  
+  // Should have received the initial message (this would fail with race condition)
+  expect(response).toContain('RECEIVED: initial-message');
+  
+  // Should have received the test message
+  expect(response).toContain('RECEIVED: test-message');
+  
+  await proxy.stop();
+});
+
+export default tap.start();