[express] Address PR feedback.

Author: alloy

docs/API.md

@@ -144,7 +144,7 @@ Each integration also has its own list of default tags. These tags get automatic
 |------------------|---------------------------|----------------------------------------|
 | service          | *Service name of the app* | The service name for this integration. |
 | validateStatus   | `code => code < 500`      | Callback function to determine if there was an error. It should take a status code as its only parameter and return `true` for success or `false` for errors. |
-| recordHeaders    | `[]`                      | An array of headers to include in the span metadata. |
+| headers          | `[]`                      | An array of headers to include in the span metadata. |
 
 <h3 id="graphql">graphql</h3>
 

src/plugins/express.js

@@ -9,7 +9,7 @@ const pathToRegExp = require('path-to-regexp')
 const OPERATION_NAME = 'express.request'
 
 function createWrapMethod (tracer, config) {
-  const recordHeaders = config.recordHeaders ? config.recordHeaders.map(key => key.toLowerCase()) : []
+  const headersToRecord = Array.isArray(config.headers) ? config.headers.map(key => key.toLowerCase()) : []
 
   const validateStatus = typeof config.validateStatus === 'function'
     ? config.validateStatus
@@ -48,7 +48,7 @@ function createWrapMethod (tracer, config) {
         span.setTag(Tags.ERROR, true)
       }
 
-      recordHeaders.forEach(key => {
+      headersToRecord.forEach(key => {
         const value = req.headers[key]
         if (value) {
           span.setTag(`http.headers.${key}`, value)

test/plugins/express.spec.js

@@ -547,7 +547,7 @@ describe('Plugin', () => {
           config = {
             service: 'custom',
             validateStatus: code => code < 400,
-            recordHeaders: ['User-Agent']
+            headers: ['User-Agent']
           }
 
           return agent.load(plugin, 'express', config)