Fix for corner-case in which no response was returned if the socket was immediately closed

Author: iAlex97

src/smtp/smtp.ts

@@ -15,14 +15,19 @@ export const checkSMTP = async (
 ): Promise<OutputFormat> => {
   const timeout = 1000 * 10 // 10 seconds
   return new Promise(r => {
+    let receivedData: boolean = false;
     const socket = net.createConnection(25, exchange)
     socket.setEncoding('ascii')
     socket.setTimeout(timeout)
     socket.on('error', error => {
       log('error', error)
       socket.emit('fail', error)
     })
-
+    socket.on('close', hadError => {
+      if (!receivedData && !hadError) {
+        socket.emit('fail', 'Mail server closed connection without sending any data.')
+      }
+    })
     socket.on('fail', msg => {
       r(createOutput('smtp', msg))
       if (socket.writable && !socket.destroyed) {
@@ -65,6 +70,7 @@ export const checkSMTP = async (
 
     socket.on('connect', () => {
       socket.on('data', msg => {
+        receivedData = true;
         log('data', msg)
         if (hasCode(msg, 220) || hasCode(msg, 250)) {
           socket.emit('next', msg)

test/__snapshots__/index.test.ts.snap

@@ -100,6 +100,31 @@ Object {
 }
 `;
 
+exports[`validation tests fails with bad mailbox 3`] = `
+Object {
+  "reason": "smtp",
+  "valid": false,
+  "validators": Object {
+    "disposable": Object {
+      "valid": true,
+    },
+    "mx": Object {
+      "valid": true,
+    },
+    "regex": Object {
+      "valid": true,
+    },
+    "smtp": Object {
+      "reason": "Mailbox not found.",
+      "valid": false,
+    },
+    "typo": Object {
+      "valid": true,
+    },
+  },
+}
+`;
+
 exports[`validation tests fails with bad regex 1`] = `
 Object {
   "reason": "regex",

test/index.test.ts

@@ -5,6 +5,15 @@ import { validate } from '../src/index'
 const elevenSeconds = 11 * 1000
 
 describe('validation tests', () => {
+  it('fails without sending data', async () => {
+    const res = await validate({
+      email: 'jubao@le.com',
+      sender: 'jubao@le.com',
+      validateTypo: false,
+      validateDisposable: false,
+    })
+    console.log(res)
+  }, 30000)
   it('fails with bad regex', async () => {
     const res = await validate('david.gmail.com')
     expect(res.valid).toBe(false)