feat: add optional end event for piping (#1926)

This will allow streams to end. We haven't done this because it allows a stream to be reopened and data to be continued to be read. 

Adds `endOnClose` to stream options so the stream will emit the end event when the port is closed. This will signal any piped parsers to end as well. If the port is reopened the parsers won’t function.

Author: reconbot

packages/stream/stream.js

@@ -10,6 +10,7 @@ const FLOWCONTROLS = Object.freeze(['xon', 'xoff', 'xany', 'rtscts'])
 
 const defaultSettings = Object.freeze({
   autoOpen: true,
+  endOnClose: false,
   baudRate: 9600,
   dataBits: 8,
   hupcl: true,
@@ -432,6 +433,9 @@ SerialPort.prototype.close = function(callback, disconnectError) {
       this.closing = false
       debug('binding.close', 'finished')
       this.emit('close', disconnectError)
+      if (this.settings.endOnClose) {
+        this.emit('end')
+      }
       if (callback) {
         callback.call(this, disconnectError)
       }

packages/stream/stream.test.js

@@ -439,7 +439,7 @@ describe('SerialPort', () => {
     })
 
     describe('#close', () => {
-      it('emits a close event', done => {
+      it('emits a close event for writing consumers', done => {
         const port = new SerialPort('/dev/exists', () => {
           port.on('close', () => {
             assert.isFalse(port.isOpen)
@@ -449,6 +449,27 @@ describe('SerialPort', () => {
         })
       })
 
+      it('emits an "end" event for reading consumers when endOnClose is true', done => {
+        const port = new SerialPort('/dev/exists', { endOnClose: true })
+        port.on('open', () => {
+          port.on('end', () => {
+            assert.isFalse(port.isOpen)
+            done()
+          })
+          port.close()
+        })
+      })
+
+      it('doesn\'t emit an "end" event for reading consumers when endOnClose is false', done => {
+        const port = new SerialPort('/dev/exists')
+        port.on('open', () => {
+          port.on('end', () => {
+            done(new Error('Should not have ended'))
+          })
+          port.close(() => done())
+        })
+      })
+
       it('has a close callback', done => {
         const port = new SerialPort('/dev/exists', () => {
           port.close(() => {