From 7eba938a22a1b2dc1b09e5a3b76a23bd0f66f7e1 Mon Sep 17 00:00:00 2001
From: Stephen Belanger <admin@stephenbelanger.com>
Date: Thu, 17 Sep 2020 12:05:11 -0700
Subject: [PATCH] Use diagnostics_channel in layers

---
 lib/layer.js                |  40 ++++++++++++++
 test/diagnostics-channel.js | 104 ++++++++++++++++++++++++++++++++++++
 2 files changed, 144 insertions(+)
 create mode 100644 test/diagnostics-channel.js

diff --git a/lib/layer.js b/lib/layer.js
index 60a737f..ca8abbb 100644
--- a/lib/layer.js
+++ b/lib/layer.js
@@ -15,6 +15,18 @@
 var pathRegexp = require('path-to-regexp')
 var debug = require('debug')('router:layer')
 
+/**
+ * Diagnostic channels
+ * @private
+ */
+var onHandleRequest
+var onHandleError
+try {
+  var dc = require('diagnostics_channel')
+  onHandleRequest = dc.channel('express.layer.handle_request')
+  onHandleError = dc.channel('express.layer.handle_error')
+} catch (err) { }
+
 /**
  * Module variables.
  * @private
@@ -41,6 +53,7 @@ function Layer(path, options, fn) {
   this.params = undefined
   this.path = undefined
   this.regexp = pathRegexp(path, this.keys = [], opts)
+  this.routingPath = path
 
   // set fast path flags
   this.regexp.fast_star = path === '*'
@@ -65,9 +78,23 @@ Layer.prototype.handle_error = function handle_error(error, req, res, next) {
     return next(error)
   }
 
+  req.layerStack = req.layerStack || []
+  req.layerStack.push(this)
+
+  if (onHandleError && onHandleError.shouldPublish()) {
+    onHandleError.publish({
+      error: error,
+      request: req,
+      response: res,
+      layer: this
+    })
+  }
+
   try {
     fn(error, req, res, next)
+    req.layerStack.pop()
   } catch (err) {
+    req.layerStack.pop()
     next(err)
   }
 }
@@ -89,9 +116,22 @@ Layer.prototype.handle_request = function handle(req, res, next) {
     return next()
   }
 
+  req.layerStack = req.layerStack || []
+  req.layerStack.push(this)
+
+  if (onHandleRequest && onHandleRequest.shouldPublish()) {
+    onHandleRequest.publish({
+      request: req,
+      response: res,
+      layer: this
+    })
+  }
+
   try {
     fn(req, res, next)
+    req.layerStack.pop()
   } catch (err) {
+    req.layerStack.pop()
     next(err)
   }
 }
diff --git a/test/diagnostics-channel.js b/test/diagnostics-channel.js
new file mode 100644
index 0000000..b457d04
--- /dev/null
+++ b/test/diagnostics-channel.js
@@ -0,0 +1,104 @@
+
+var Router = require('../')
+  , assert = require('assert');
+
+var dc = require('diagnostics_channel');
+var onHandleRequest = dc.channel('express.layer.handle_request');
+var onHandleError = dc.channel('express.layer.handle_error');
+
+function mapProp(prop) {
+  return function mapped(obj) {
+    return obj[prop];
+  };
+}
+
+function mapAndJoin(prop) {
+  return function (list) {
+    return list.map(mapProp(prop)).join('');
+  }
+}
+
+function noop() { }
+
+describe('diagnostics_channel', function () {
+  var joinLayerStack = mapAndJoin('routingPath');
+  var handleRequest;
+  var handleError;
+
+  onHandleRequest.subscribe(function (message) {
+    handleRequest = message;
+  });
+
+  onHandleError.subscribe(function (message) {
+    handleError = message;
+  });
+
+  it('use has no layers with a path', function (done) {
+    var router = new Router();
+
+    router.use(function (req, res) {
+      res.end();
+    });
+
+    function end() {
+      assert.strictEqual(joinLayerStack(handleRequest.request.layerStack), '/');
+      done();
+    }
+
+    router.handle({ url: '/', method: 'GET' }, { end }, noop);
+  });
+
+  it('regular routes have a layer with a path', function (done) {
+    var router = new Router();
+
+    router.get('/hello/:name', function (req, res) {
+      res.end();
+    });
+
+    function end() {
+      assert.strictEqual(joinLayerStack(handleRequest.request.layerStack), '/hello/:name/');
+      done();
+    }
+
+    router.handle({ url: '/hello/world', method: 'GET' }, { end }, noop);
+  });
+
+  it('nested routes have multiple layers with paths', function (done) {
+    var outer = new Router();
+    var inner = new Router();
+
+    inner.get('/:name', function (req, res) {
+      res.end();
+    });
+
+    outer.use('/hello', inner);
+
+    function end() {
+      assert.strictEqual(joinLayerStack(handleRequest.request.layerStack), '/hello/:name/');
+      done();
+    }
+
+    outer.handle({ url: '/hello/world', method: 'GET' }, { end }, noop);
+  });
+
+  it('errors send through a different channel', function (done) {
+    var router = new Router();
+    var error = new Error('fail');
+
+    router.get('/hello/:name', function (req, res) {
+      throw error;
+    });
+
+    router.use(function (err, req, res, next) {
+      res.end();
+    });
+
+    function end() {
+      assert.strictEqual(joinLayerStack(handleRequest.request.layerStack), '/hello/:name/');
+      assert.strictEqual(handleError.error, error);
+      done();
+    }
+
+    router.handle({ url: '/hello/world', method: 'GET' }, { end }, noop);
+  });
+});