fs: lazy load the promises impl

jasnell · MylesBorins · commit 2d2897855fa5 · 2018-05-22T14:13:28.000-04:00
PR-URL: #20766 Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com> Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Minwoo Jung <minwoo@nodesource.com> Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com> Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
diff --git a/lib/fs.js b/lib/fs.js
@@ -60,7 +60,6 @@ const { Readable, Writable } = require('stream');
 const EventEmitter = require('events');
 const { FSReqWrap, statValues, kFsStatsFieldsLength } = binding;
 const { FSEvent } = process.binding('fs_event_wrap');
-const promises = require('internal/fs/promises');
 const internalFS = require('internal/fs/utils');
 const { getPathFromURL } = require('internal/url');
 const internalUtil = require('internal/util');
@@ -89,14 +88,18 @@ const {
 CHAR_BACKWARD_SLASH,
 } = require('internal/constants');
 
-let warn = true;
+// Lazy loaded
+let promises;
+
+let promisesWarn = true;
 
 Object.defineProperty(fs, 'promises', {
 configurable: true,
 enumerable: false,
 get() {
- if (warn) {
- warn = false;
+ if (promisesWarn) {
+ promises = require('internal/fs/promises');
+ promisesWarn = false;
 process.emitWarning('The fs.promises API is experimental',
 'ExperimentalWarning');
 }

-Original file line number
+Diff line change
 constEventEmitter=require('events');
 const{ FSReqWrap, statValues, kFsStatsFieldsLength }=binding;
 const{ FSEvent }=process.binding('fs_event_wrap');
 -constpromises=require('internal/fs/promises');
 constinternalFS=require('internal/fs/utils');
 const{ getPathFromURL }=require('internal/url');
 constinternalUtil=require('internal/util');
 CHAR_BACKWARD_SLASH,
 }=require('internal/constants');
 -letwarn=true;
 +// Lazy loaded
 +letpromises;
++
 +letpromisesWarn=true;
 Object.defineProperty(fs,'promises',{
 configurable: true,
 enumerable: false,
 get(){
 -if(warn){
 -warn=false;
 +if(promisesWarn){
 +promises=require('internal/fs/promises');
 +promisesWarn=false;
 process.emitWarning('The fs.promises API is experimental',
 'ExperimentalWarning');
+}