[pinpoint-apm#86] express error case condition

lib/instrumentation/module/express.js

@@ -6,6 +6,7 @@
 
 'use strict'
 
+const util = require('util')
 const shimmer = require('shimmer')
 const ServiceTypeCode = require('../../constant/service-type').ServiceTypeCode
 const log = require('../../utils/logger')
@@ -17,7 +18,8 @@ const ExpressMethodDescriptorBuilder = require('../../context/express-method-des
 const semver = require('semver')
 
 const parameterizedLayerPathSymbol = Symbol('PinpointParameterizedLayerPathSymbol')
-const layerPatchedSymbol = Symbol('layer-patched')
+const layerPatchedSymbol = Symbol('PinpointLayerPatched')
+const errorReportedSymbol = Symbol('PinpointErrorReported')
 
 // https://github.com/elastic/apm-agent-nodejs/blob/master/lib/instrumentation/modules/express.js
 module.exports = function (agent, version, express) {
@@ -98,6 +100,9 @@ module.exports = function (agent, version, express) {
           }
         } else {
           handle = function (err, req, res, next) {
+            if (shouldReport(err)) {
+
+            }
             return origin.apply(this, arguments)
           }
         }
@@ -131,6 +136,24 @@ module.exports = function (agent, version, express) {
     obj[prop].push(value)
   }
 
+  function shouldReport(error) {
+    if (typeof error === 'string') {
+      return true
+    }
+    if (isError(error) && !error[errorReportedSymbol]) {
+      error[errorReportedSymbol] = true
+      return true
+    }
+    return false
+  }
+
+  function isError(error) {
+    if (!util.types) {
+      return util.isError(error)
+    }
+    return util.types.isNativeError(error)
+  }
+
   function recordHandle(original, objectName, layerName, appAllMethodDescriptor, handlerMethodDescriptor, layerPath) {
     return function (req) {
       const trace = agent.traceContext.currentTraceObject()