Stringify userId and anonymousId

Ref: https://segment.atlassian.net/browse/LIB-29

Our API truncates bignum values. This is problematic because this library has historically accepted Numbers as userIds and anonymousIds. To workaround the truncation, this library needs to stringify userId and anonymousId on the client. In the future we can make a breaking change and restrict the library to only accepting String ids, but for now we are keeping backward compatibility.

index.js

@@ -8,6 +8,7 @@ const retries = require('axios-retry')
 const ms = require('ms')
 const uid = require('crypto-token')
 const version = require('./package.json').version
+const isString = require('lodash.isstring')
 
 const setImmediate = global.setImmediate || process.nextTick.bind(process)
 const noop = () => {}
@@ -158,6 +159,16 @@ class Analytics {
       message.messageId = `node-${uid(32)}`
     }
 
+    // Historically this library has accepted strings and numbers as IDs.
+    // However, our spec only allows strings. To avoid breaking compatibility,
+    // we'll coerce these to strings if they aren't already.
+    if (message.anonymousId && !isString(message.anonymousId)) {
+      message.anonymousId = JSON.stringify(message.anonymousId)
+    }
+    if (message.userId && !isString(message.userId)) {
+      message.userId = JSON.stringify(message.userId)
+    }
+
     this.queue.push({ message, callback })
 
     if (!this.flushed) {

package.json

@@ -39,6 +39,7 @@
     "axios-retry": "^3.0.1",
     "commander": "^2.9.0",
     "crypto-token": "^1.0.1",
+    "lodash.isstring": "^4.0.1",
     "ms": "^2.0.0",
     "remove-trailing-slash": "^0.1.0"
   },

test.js

@@ -141,6 +141,58 @@ test('enqueue - add a message to the queue', t => {
   })
 })
 
+test('enqueue - stringify userId', t => {
+  const client = createClient()
+
+  client.track({
+    userId: 10,
+    event: 'event'
+  }, noop)
+
+  t.is(client.queue.length, 1)
+
+  const item = client.queue.pop()
+
+  t.is(item.message.anonymousId, undefined)
+  t.is(item.message.userId, '10')
+})
+
+test('enqueue - stringify anonymousId', t => {
+  const client = createClient()
+
+  client.screen({
+    anonymousId: 157963456373623802,
+    name: 'screen name'
+  }, noop)
+
+  t.is(client.queue.length, 1)
+
+  const item = client.queue.pop()
+
+  t.is(item.message.userId, undefined)
+  // v8 will lose precision for big numbers.
+  t.is(item.message.anonymousId, '157963456373623800')
+})
+
+test('enqueue - stringify ids handles strings', t => {
+  const client = createClient()
+
+  client.screen({
+    anonymousId: '15796345',
+    // We're explicitly testing the behaviour of the library if a customer
+    // uses a String constructor.
+    userId: new String('prateek'), // eslint-disable-line no-new-wrappers
+    name: 'screen name'
+  }, noop)
+
+  t.is(client.queue.length, 1)
+
+  const item = client.queue.pop()
+
+  t.is(item.message.anonymousId, '15796345')
+  t.is(item.message.userId.toString(), 'prateek')
+})
+
 test('enqueue - don\'t modify the original message', t => {
   const client = createClient()
   const message = { event: 'test' }