From f71fdfdf353172d1418a1690ae5493c52692d57d Mon Sep 17 00:00:00 2001
From: Jacob Heun <jacobheun@gmail.com>
Date: Mon, 12 Nov 2018 15:43:32 +0100
Subject: [PATCH] feat: conditionally emit errors

test: add tests for emit override
---
 src/index.js        | 18 ++++++++++++++++++
 test/create.spec.js | 21 +++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/src/index.js b/src/index.js
index 40ec5f4563..00a9e6e51f 100644
--- a/src/index.js
+++ b/src/index.js
@@ -51,7 +51,10 @@ class Node extends EventEmitter {
     this._transport = [] // Transport instances/references
     this._discovery = [] // Discovery service instances/references
 
+    // create the switch, and listen for errors
     this._switch = new Switch(this.peerInfo, this.peerBook, _options.switch)
+    this._switch.on('error', (...args) => this.emit('error', ...args))
+
     this.stats = this._switch.stats
     this.connectionManager = new ConnectionManager(this, _options.connectionManager)
 
@@ -162,6 +165,21 @@ class Node extends EventEmitter {
     })
   }
 
+  /**
+   * Overrides EventEmitter.emit to conditionally emit errors
+   * if there is a handler. If not, errors will be logged.
+   * @param {string} eventName
+   * @param  {...any} args
+   * @returns {void}
+   */
+  emit (eventName, ...args) {
+    if (eventName === 'error' && !this._events.error) {
+      log.error(...args)
+    } else {
+      super.emit(eventName, ...args)
+    }
+  }
+
   /**
    * Starts the libp2p node and all sub services
    *
diff --git a/test/create.spec.js b/test/create.spec.js
index 17b1d52d4c..e832771fe5 100644
--- a/test/create.spec.js
+++ b/test/create.spec.js
@@ -80,4 +80,25 @@ describe('libp2p creation', () => {
       done()
     })
   })
+
+  it('should not throw errors from switch if node has no error listeners', (done) => {
+    createNode([], {}, (err, node) => {
+      expect(err).to.not.exist()
+
+      node._switch.emit('error', new Error('bad things'))
+      done()
+    })
+  })
+
+  it('should emit errors from switch if node has error listeners', (done) => {
+    const error = new Error('bad things')
+    createNode([], {}, (err, node) => {
+      expect(err).to.not.exist()
+      node.once('error', (err) => {
+        expect(err).to.eql(error)
+        done()
+      })
+      node._switch.emit('error', error)
+    })
+  })
 })