repl: disable blocking completions by default

It’s not okay for the REPL to be blocked for multiple seconds after entering `require('` because the completion is performing blocking fs operations on potentially huge directories. Turning the REPL completion function asynchronous would be the right thing to do here, but unfortunately the way the code is structured doesn’t play well with that (in particular, it breaks the preview feature). Therefore, disable these blocking calls by default. Refs: #33282 (comment) PR-URL: #36564 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]>

Author: addaleax

lib/repl.js

@@ -58,6 +58,7 @@ const{
  Promise,
  PromiseRace,
  RegExp,
+ RegExpPrototypeTest,
  Set,
  StringPrototypeCharAt,
  StringPrototypeIncludes,
@@ -267,6 +268,7 @@ function REPLServer(prompt,
 configurable: true
 });
 
+this.allowBlockingCompletions=!!options.allowBlockingCompletions;
 this.useColors=!!options.useColors;
 this._domain=options.domain||domain.create();
 this.useGlobal=!!useGlobal;
@@ -1186,7 +1188,8 @@ function complete(line, callback){
 if(completeOn.length){
 filter=completeOn;
 }
-}elseif(requireRE.test(line)){
+}elseif(RegExpPrototypeTest(requireRE,line)&&
+this.allowBlockingCompletions){
 // require('...<Tab>')
 constextensions=ObjectKeys(this.context.require.extensions);
 constindexes=extensions.map((extension)=>`index${extension}`);
@@ -1244,7 +1247,8 @@ function complete(line, callback){
 if(!subdir){
 completionGroups.push(_builtinLibs);
 }
-}elseif(fsAutoCompleteRE.test(line)){
+}elseif(RegExpPrototypeTest(fsAutoCompleteRE,line)&&
+this.allowBlockingCompletions){
 [completionGroups,completeOn]=completeFSFunctions(line);
 // Handle variable member lookup.
 // We support simple chained expressions like the following (no function

test/parallel/test-repl-tab-complete.js

@@ -51,7 +51,12 @@ function getNoResultsFunction(){
 
 constworks=[['inner.one'],'inner.o'];
 constputIn=newArrayStream();
-consttestMe=repl.start('',putIn);
+consttestMe=repl.start({
+prompt: '',
+input: putIn,
+output: process.stdout,
+allowBlockingCompletions: true
+});
 
 // Some errors are passed to the domain, but do not callback
 testMe._domain.on('error',assert.ifError);