Add callback support to SlackBot::{send,reply}

package.json

@@ -26,8 +26,7 @@
   "dependencies": {
     "@slack/client": "3.16.1-sec.2",
     "bluebird": "^3.5.1",
-    "lodash": "^4.17.10",
-    "es6-promise": "~4.2.5"
+    "lodash": "^4.17.10"
   },
   "peerDependencies": {
     "hubot": ">= 2.0.0"

src/bot.coffee

@@ -2,7 +2,7 @@
 {SlackTextMessage, ReactionMessage, PresenceMessage}                              = require "./message"
 SlackClient                                                                       = require "./client"
 pkg                                                                               = require "../package"
-Promise = global.Promise || require('es6-promise')
+Promise = require("bluebird");
 
 class SlackBot extends Adapter
 
@@ -84,10 +84,11 @@ class SlackBot extends Adapter
     callback = ->
     if typeof(messages[messages.length - 1]) == 'function'
       callback = messages.pop()
-    for message in messages
+    messagePromises = messages.map (message) =>
+      return Promise.resolve() if typeof(message) is 'function'
       # NOTE: perhaps do envelope manipulation here instead of in the client (separation of concerns)
       @client.send(envelope, message) unless message is ""
-    Promise.all(messages).then(callback.bind(null, null), callback)
+    Promise.all(messagePromises).then(callback.bind(null, null), callback)
 
   ###*
   # Hubot is replying to a Slack message
@@ -99,12 +100,13 @@ class SlackBot extends Adapter
     callback = ->
     if typeof(messages[messages.length - 1]) == 'function'
       callback = messages.pop()
-    for message in messages
+    messagePromises = messages.map (message) =>
+      return Promise.resolve() if typeof(message) is 'function'
       if message isnt ""
         # TODO: channel prefix matching should be removed
         message = "<@#{envelope.user.id}>: #{message}" unless envelope.room[0] is "D"
         @client.send envelope, message
-    Promise.all(messages).then(callback.bind(null, null), callback)
+    Promise.all(messagePromises).then(callback.bind(null, null), callback)
 
   ###*
   # Hubot is setting the Slack conversation topic