stream: refactor lazyLoadPromises

PR-URL: https://github.com/nodejs/node/pull/34354
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/stream.js

@@ -49,28 +49,30 @@ Stream.PassThrough = require('_stream_passthrough');
 Stream.pipeline = pipeline;
 Stream.finished = eos;
 
+function lazyLoadPromises() {
+  if (promises === null) promises = require('stream/promises');
+  return promises;
+}
+
 ObjectDefineProperty(Stream, 'promises', {
   configurable: true,
   enumerable: true,
   get() {
-    if (promises === null) promises = require('stream/promises');
-    return promises;
+    return lazyLoadPromises();
   }
 });
 
 ObjectDefineProperty(pipeline, customPromisify, {
   enumerable: true,
   get() {
-    if (promises === null) promises = require('stream/promises');
-    return promises.pipeline;
+    return lazyLoadPromises().pipeline;
   }
 });
 
 ObjectDefineProperty(eos, customPromisify, {
   enumerable: true,
   get() {
-    if (promises === null) promises = require('stream/promises');
-    return promises.finished;
+    return lazyLoadPromises().finished;
   }
 });