fix express resource with multiple middlewares matching the route

src/plugins/express.js

@@ -97,11 +97,11 @@ function createWrapRouterMethod (tracer) {
         const handleError = layer.handle_error
 
         layer.handle_request = (req, res, next) => {
-          return handleRequest.call(layer, req, res, wrapNext(tracer, req, next))
+          return handleRequest.call(layer, req, res, wrapNext(tracer, layer, req, next))
         }
 
         layer.handle_error = (error, req, res, next) => {
-          return handleError.call(layer, error, req, res, wrapNext(tracer, req, next))
+          return handleError.call(layer, error, req, res, wrapNext(tracer, layer, req, next))
         }
 
         layer._datadog_matchers = matchers
@@ -112,8 +112,21 @@ function createWrapRouterMethod (tracer) {
   }
 }
 
-function wrapNext (tracer, req, next) {
+function wrapNext (tracer, layer, req, next) {
   if (req._datadog_trace_patched) {
+    const context = tracer._context
+    const originalNext = next
+
+    next = context.bind(function () {
+      const paths = context.get('express.paths')
+
+      if (paths && layer.path && !layer.regexp.fast_star) {
+        paths.pop()
+      }
+
+      originalNext.apply(null, arguments)
+    })
+
     return tracer._context.bind(next)
   }
 

test/plugins/express.spec.js

@@ -140,6 +140,38 @@ describe('Plugin', () => {
         })
       })
 
+      it('should only keep the last matching path of a middleware stack', done => {
+        const app = express()
+        const router = express.Router()
+
+        router.use('/', (req, res, next) => next())
+        router.use('*', (req, res, next) => next())
+        router.use('/bar', (req, res, next) => next())
+        router.use('/bar', (req, res, next) => {
+          res.status(200).send()
+        })
+
+        app.use('/', (req, res, next) => next())
+        app.use('*', (req, res, next) => next())
+        app.use('/foo/bar', (req, res, next) => next())
+        app.use('/foo', router)
+
+        getPort().then(port => {
+          agent
+            .use(traces => {
+              expect(traces[0][0]).to.have.property('resource', '/foo/bar')
+            })
+            .then(done)
+            .catch(done)
+
+          appListener = app.listen(port, 'localhost', () => {
+            axios
+              .get(`http://localhost:${port}/foo/bar`)
+              .catch(done)
+          })
+        })
+      })
+
       it('should support asynchronous routers', done => {
         const app = express()
         const router = express.Router()