chore: add callback functionality back in

This also improves the performance for multi / batch commands a lot.
The reason is that now there are only callbacks internally even if
a promise is going to be returned in the end.

lib/individualCommands.js

@@ -1,6 +1,6 @@
 'use strict'
 
-const Command = require('./command')
+const { Command, MultiCommand } = require('./command')
 const debug = require('./debug')
 const Multi = require('./multi')
 const utils = require('./utils')
@@ -29,16 +29,20 @@ function selectCallback(client, db) {
       // Store db in this.selectDb to restore it on reconnect
       client.selectedDb = db
     }
-    return err || res
+    return [err, res]
   }
 }
 
 RedisClient.prototype.select = function select(db) {
-  return this.internalSendCommand(new Command('select', [db], null, selectCallback(this, db)))
+  const command = new Command('select', [db])
+  command.transformer = selectCallback(this, db)
+  return this.internalSendCommand(command)
 }
 
 Multi.prototype.select = function select(db) {
-  this._queue.push(new Command('select', [db], null, selectCallback(this._client, db)))
+  const command = new MultiCommand('select', [db])
+  command.transformer = selectCallback(this._client, db)
+  this._queue.push(command)
   return this
 }
 
@@ -51,7 +55,9 @@ RedisClient.prototype.monitor = function monitor() {
     // be properly processed. If this is not the case, it's not an issue either.
     this._monitoring = true
   }
-  return this.internalSendCommand(new Command('monitor', [], callOnWrite))
+  const command = new Command('monitor', [])
+  command.callOnWrite = callOnWrite
+  return this.internalSendCommand(command)
 }
 
 // Only works with batch, not in a transaction
@@ -62,7 +68,9 @@ Multi.prototype.monitor = function monitor() {
     const callOnWrite = () => {
       this._client._monitoring = true
     }
-    this._queue.push(new Command('monitor', [], callOnWrite))
+    const command = new MultiCommand('monitor', [])
+    command.callOnWrite = callOnWrite
+    this._queue.push(command)
     return this
   }
   // Set multi monitoring to indicate the exec that it should abort
@@ -84,9 +92,9 @@ function quitCallback(client) {
       // or the offline queue is deactivated and the command was rejected right away
       // or the stream is not writable
       // or while sending the quit, the connection ended / closed
-      return 'OK'
+      return [null, 'OK']
     }
-    return err || res
+    return [err, res]
   }
 }
 
@@ -95,7 +103,9 @@ RedisClient.prototype.quit = function quit() {
   //
   // Allow the quit command to be fired as soon as possible to prevent it
   // landing in the offline queue. this.ready = this.offlineQueue.length === 0;
-  const backpressureIndicator = this.internalSendCommand(new Command('quit', [], null, quitCallback(this)))
+  const command = new Command('quit', [])
+  command.transformer = quitCallback(this)
+  const backpressureIndicator = this.internalSendCommand(command)
   // Calling quit should always end the connection, no matter if there's a connection or not
   this._closing = true
   this.ready = false
@@ -109,7 +119,10 @@ Multi.prototype.quit = function quit() {
     this._client._closing = true
     this._client.ready = false
   }
-  this._queue.push(new Command('quit', [], callOnWrite, quitCallback(this._client)))
+  const command = new MultiCommand('quit', [])
+  command.callOnWrite = callOnWrite
+  command.transformer = quitCallback(this._client)
+  this._queue.push(command)
   return this
 }
 
@@ -122,7 +135,7 @@ Multi.prototype.quit = function quit() {
 function infoCallback(client) {
   return function (err, res) {
     if (err) {
-      return err
+      return [err, undefined]
     }
 
     if (typeof res !== 'string') {
@@ -171,32 +184,36 @@ function infoCallback(client) {
     }
 
     client.serverInfo = obj
-    return res
+    return [null, res]
   }
 }
 
 // Store info in this.serverInfo after each call
 RedisClient.prototype.info = function info(section) {
   const args = section ? [section] : []
-  return this.internalSendCommand(new Command('info', args, null, infoCallback(this)))
+  const command = new Command('info', args)
+  command.transformer = infoCallback(this)
+  return this.internalSendCommand(command)
 }
 
 Multi.prototype.info = function info(section) {
   const args = section ? [section] : []
-  this._queue.push(new Command('info', args, null, infoCallback(this._client)))
+  const command = new MultiCommand('info', args)
+  command.transformer = infoCallback(this._client)
+  this._queue.push(command)
   return this
 }
 
-function authCallback(client, pass) {
+function authCallback(client) {
   return function (err, res) {
     if (err) {
       if (noPasswordIsSet.test(err.message)) {
         utils.warn(client, 'Warning: Redis server does not require a password, but a password was supplied.')
-        return 'OK'
+        return [null, 'OK']
       }
-      return err
+      return [err, undefined]
     }
-    return res
+    return [null, res]
   }
 }
 
@@ -207,7 +224,9 @@ RedisClient.prototype.auth = function auth(pass) {
   this._options.password = pass
   const ready = this.ready
   this.ready = ready || this.offlineQueue.length === 0
-  const tmp = this.internalSendCommand(new Command('auth', [pass], null, authCallback(this, pass)))
+  const command = new Command('auth', [pass])
+  command.transformer = authCallback(this)
+  const tmp = this.internalSendCommand(command)
   this.ready = ready
   return tmp
 }
@@ -218,7 +237,9 @@ Multi.prototype.auth = function auth(pass) {
 
   // Stash auth for connect and reconnect.
   this._client._options.password = pass
-  this._queue.push(new Command('auth', [pass], null, authCallback(this._client)))
+  const command = new MultiCommand('auth', [pass])
+  command.transformer = authCallback(this._client)
+  this._queue.push(command)
   return this
 }
 
@@ -233,7 +254,9 @@ RedisClient.prototype.client = function client(...arr) {
       }
     }
   }
-  return this.internalSendCommand(new Command('client', arr, callOnWrite))
+  const command = new Command('client', arr)
+  command.callOnWrite = callOnWrite
+  return this.internalSendCommand(command)
 }
 
 Multi.prototype.client = function client(...arr) {
@@ -247,7 +270,9 @@ Multi.prototype.client = function client(...arr) {
       }
     }
   }
-  this._queue.push(new Command('client', arr, callOnWrite))
+  const command = new MultiCommand('client', arr)
+  command.callOnWrite = callOnWrite
+  this._queue.push(command)
   return this
 }
 
@@ -255,14 +280,18 @@ RedisClient.prototype.subscribe = function subscribe(...arr) {
   const callOnWrite = () => {
     this._pubSubMode = this._pubSubMode || this.commandQueue.length + 1
   }
-  return this.internalSendCommand(new Command('subscribe', arr, callOnWrite))
+  const command = new Command('subscribe', arr)
+  command.callOnWrite = callOnWrite
+  return this.internalSendCommand(command)
 }
 
 Multi.prototype.subscribe = function subscribe(...arr) {
   const callOnWrite = () => {
     this._client._pubSubMode = this._client._pubSubMode || this._client.commandQueue.length + 1
   }
-  this._queue.push(new Command('subscribe', arr, callOnWrite))
+  const command = new MultiCommand('subscribe', arr)
+  command.callOnWrite = callOnWrite
+  this._queue.push(command)
   return this
 }
 
@@ -272,7 +301,9 @@ RedisClient.prototype.unsubscribe = function unsubscribe(...arr) {
     // value is manipulated in the callback
     this._pubSubMode = this._pubSubMode || this.commandQueue.length + 1
   }
-  return this.internalSendCommand(new Command('unsubscribe', arr, callOnWrite))
+  const command = new Command('unsubscribe', arr)
+  command.callOnWrite = callOnWrite
+  return this.internalSendCommand(command)
 }
 
 Multi.prototype.unsubscribe = function unsubscribe(...arr) {
@@ -281,7 +312,9 @@ Multi.prototype.unsubscribe = function unsubscribe(...arr) {
     // value is manipulated in the callback
     this._client._pubSubMode = this._client._pubSubMode || this._client.commandQueue.length + 1
   }
-  this._queue.push(new Command('unsubscribe', arr, callOnWrite))
+  const command = new MultiCommand('unsubscribe', arr)
+  command.callOnWrite = callOnWrite
+  this._queue.push(command)
   return this
 }
 
@@ -289,14 +322,18 @@ RedisClient.prototype.psubscribe = function psubscribe(...arr) {
   const callOnWrite = () => {
     this._pubSubMode = this._pubSubMode || this.commandQueue.length + 1
   }
-  return this.internalSendCommand(new Command('psubscribe', arr, callOnWrite))
+  const command = new Command('psubscribe', arr)
+  command.callOnWrite = callOnWrite
+  return this.internalSendCommand(command)
 }
 
 Multi.prototype.psubscribe = function psubscribe(...arr) {
   const callOnWrite = () => {
     this._client._pubSubMode = this._client._pubSubMode || this._client.commandQueue.length + 1
   }
-  this._queue.push(new Command('psubscribe', arr, callOnWrite))
+  const command = new MultiCommand('psubscribe', arr)
+  command.callOnWrite = callOnWrite
+  this._queue.push(command)
   return this
 }
 
@@ -306,7 +343,9 @@ RedisClient.prototype.punsubscribe = function punsubscribe(...arr) {
     // value is manipulated in the callback
     this._pubSubMode = this._pubSubMode || this.commandQueue.length + 1
   }
-  return this.internalSendCommand(new Command('punsubscribe', arr, callOnWrite))
+  const command = new Command('punsubscribe', arr)
+  command.callOnWrite = callOnWrite
+  return this.internalSendCommand(command)
 }
 
 Multi.prototype.punsubscribe = function punsubscribe(...arr) {
@@ -315,6 +354,8 @@ Multi.prototype.punsubscribe = function punsubscribe(...arr) {
     // value is manipulated in the callback
     this._client._pubSubMode = this._client._pubSubMode || this._client.commandQueue.length + 1
   }
-  this._queue.push(new Command('punsubscribe', arr, callOnWrite))
+  const command = new MultiCommand('punsubscribe', arr)
+  command.callOnWrite = callOnWrite
+  this._queue.push(command)
   return this
 }