string_decoder: lazy loaded

PR-URL: https://github.com/nodejs/node/pull/20567
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/readline.js b/lib/readline.js
index 124fc8111b..89dd1b84f2 100644
--- a/lib/readline.js
+++ b/lib/readline.js
@@ -35,7 +35,6 @@ const {
 const { debug, inherits } = require('util');
 const { Buffer } = require('buffer');
 const EventEmitter = require('events');
-const { StringDecoder } = require('string_decoder');
 const {
   CSI,
   emitKeys,
@@ -52,6 +51,9 @@ const {
   kClearScreenDown
 } = CSI;
 
+// Lazy load StringDecoder for startup performance.
+let StringDecoder;
+
 const kHistorySize = 30;
 const kMincrlfDelay = 100;
 // \r\n, \n, or \r followed by something other than \n
@@ -73,6 +75,9 @@ function Interface(input, output, completer, terminal) {
     return new Interface(input, output, completer, terminal);
   }
 
+  if (StringDecoder === undefined)
+    StringDecoder = require('string_decoder').StringDecoder;
+
   this._sawReturnAt = 0;
   this.isCompletionEnabled = true;
   this._sawKeyPress = false;
@@ -987,6 +992,9 @@ Interface.prototype._ttyWrite = function(s, key) {
 
 function emitKeypressEvents(stream, iface) {
   if (stream[KEYPRESS_DECODER]) return;
+
+  if (StringDecoder === undefined)
+    StringDecoder = require('string_decoder').StringDecoder;
   stream[KEYPRESS_DECODER] = new StringDecoder('utf8');
 
   stream[ESCAPE_DECODER] = emitKeys(stream);