repl: lazy-load acorn and defer vm context creation

lib/internal/repl/completion.js

@@ -33,7 +33,7 @@ const {
 const {
   kContextId,
   getREPLResourceName,
-  globalBuiltins,
+  getGlobalBuiltins,
   getReplBuiltinLibs,
   fixReplRequire,
 } = require('internal/repl/utils');
@@ -61,13 +61,6 @@ const {
   getOwnNonIndexProperties,
 } = internalBinding('util');
 
-const {
-  isIdentifierStart,
-  isIdentifierChar,
-  parse: acornParse,
-} = require('internal/deps/acorn/acorn/dist/acorn');
-const acornWalk = require('internal/deps/acorn/acorn-walk/dist/walk');
-
 const importRE = /\bimport\s*\(\s*['"`](([\w@./:-]+\/)?(?:[\w@./:-]*))(?![^'"`])$/;
 const requireRE = /\brequire\s*\(\s*['"`](([\w@./:-]+\/)?(?:[\w@./:-]*))(?![^'"`])$/;
 const fsAutoCompleteRE = /fs(?:\.promises)?\.\s*[a-z][a-zA-Z]+\(\s*["'](.*)/;
@@ -87,6 +80,8 @@ function isIdentifier(str) {
   if (str === '') {
     return false;
   }
+  const { isIdentifierStart, isIdentifierChar } =
+    require('internal/deps/acorn/acorn/dist/acorn');
   const first = StringPrototypeCodePointAt(str, 0);
   if (!isIdentifierStart(first)) {
     return false;
@@ -374,8 +369,8 @@ function complete(line, callback) {
       if (!this.useGlobal) {
         // When the context is not `global`, builtins are not own
         // properties of it.
-        // `globalBuiltins` is a `SafeSet`, not an Array-like.
-        ArrayPrototypePush(contextOwnNames, ...globalBuiltins);
+        // `getGlobalBuiltins()` is a `SafeSet`, not an Array-like.
+        ArrayPrototypePush(contextOwnNames, ...getGlobalBuiltins());
       }
       ArrayPrototypePush(completionGroups, contextOwnNames);
       if (filter !== '') addCommonWords(completionGroups);
@@ -387,6 +382,7 @@ function complete(line, callback) {
     // so in order to make it correct we add an identifier to its end (e.g. `obj.foo.x`)
     const parsableCompleteTarget = completeTarget.endsWith('.') ? `${completeTarget}x` : completeTarget;
 
+    const { parse: acornParse } = require('internal/deps/acorn/acorn/dist/acorn');
     let completeTargetAst;
     try {
       completeTargetAst = acornParse(
@@ -551,6 +547,7 @@ function findExpressionCompleteTarget(code) {
     return !result ? result : `${result}.`;
   }
 
+  const { parse: acornParse } = require('internal/deps/acorn/acorn/dist/acorn');
   let ast;
   try {
     ast = acornParse(code, { __proto__: null, sourceType: 'module', ecmaVersion: 'latest' });
@@ -625,6 +622,7 @@ function findExpressionCompleteTarget(code) {
 
   // Walk the AST for the current block of code, and check whether it contains any
   // statement or expression type that would potentially have side effects if evaluated.
+  const acornWalk = require('internal/deps/acorn/acorn-walk/dist/walk');
   let isAllowed = true;
   const disallow = () => isAllowed = false;
   acornWalk.simple(lastBodyStatement, {

lib/internal/repl/utils.js

@@ -20,10 +20,8 @@ const {
   Symbol,
 } = primordials;
 
-const { tokTypes: tt, Parser: AcornParser } =
-  require('internal/deps/acorn/acorn/dist/acorn');
-
 const { sendInspectorCommand } = require('internal/util/inspector');
+const { getLazy } = require('internal/util');
 
 const {
   ERR_INSPECTOR_NOT_AVAILABLE,
@@ -80,6 +78,9 @@ function isRecoverableError(e, code) {
       isRecoverableError(e, `(${code}`))
     return true;
 
+  const { tokTypes: tt, Parser: AcornParser } =
+    require('internal/deps/acorn/acorn/dist/acorn');
+
   let recoverable = false;
 
   // Determine if the point of any error raised is at the end of the input.
@@ -756,6 +757,8 @@ function setupReverseSearch(repl) {
 const startsWithBraceRegExp = /^\s*{/;
 const endsWithSemicolonRegExp = /;\s*$/;
 function isValidSyntax(input) {
+  const { Parser: AcornParser } =
+    require('internal/deps/acorn/acorn/dist/acorn');
   try {
     AcornParser.parse(input, {
       ecmaVersion: 'latest',
@@ -815,8 +818,9 @@ function getREPLResourceName() {
   return `REPL${nextREPLResourceNumber++}`;
 }
 
-const globalBuiltins =
-  new SafeSet(vm.runInNewContext('Object.getOwnPropertyNames(globalThis)'));
+// Creating a new context is expensive, so only do it on first use.
+const getGlobalBuiltins = getLazy(() =>
+  new SafeSet(vm.runInNewContext('Object.getOwnPropertyNames(globalThis)')));
 
 let _builtinLibs = ArrayPrototypeFilter(
   CJSModule.builtinModules,
@@ -848,7 +852,7 @@ module.exports = {
   isValidSyntax,
   kContextId,
   getREPLResourceName,
-  globalBuiltins,
+  getGlobalBuiltins,
   getReplBuiltinLibs,
   setReplBuiltinLibs,
   fixReplRequire,

lib/repl.js

@@ -89,10 +89,6 @@ const {
   makeRequireFunction,
   addBuiltinLibsToObject,
 } = require('internal/modules/helpers');
-const {
-  parse: acornParse,
-} = require('internal/deps/acorn/acorn/dist/acorn');
-const acornWalk = require('internal/deps/acorn/acorn-walk/dist/walk');
 const {
   decorateErrorStack,
   isError,
@@ -153,7 +149,7 @@ const {
   isValidSyntax,
   kContextId,
   getREPLResourceName,
-  globalBuiltins,
+  getGlobalBuiltins,
   getReplBuiltinLibs,
   setReplBuiltinLibs,
   fixReplRequire,
@@ -249,6 +245,8 @@ writer.options = { ...inspect.defaultOptions, showProxy: true };
 
 // Converts static import statement to dynamic import statement
 const toDynamicImport = (codeLine) => {
+  const { parse: acornParse } = require('internal/deps/acorn/acorn/dist/acorn');
+  const acornWalk = require('internal/deps/acorn/acorn-walk/dist/walk');
   let dynamicImportStatement = '';
   const ast = acornParse(codeLine, { __proto__: null, sourceType: 'module', ecmaVersion: 'latest' });
   acornWalk.ancestor(ast, {
@@ -1139,7 +1137,7 @@ class REPLServer extends Interface {
       });
       ArrayPrototypeForEach(ObjectGetOwnPropertyNames(globalThis), (name) => {
         // Only set properties that do not already exist as a global builtin.
-        if (!globalBuiltins.has(name)) {
+        if (!getGlobalBuiltins().has(name)) {
           ObjectDefineProperty(context, name,
                                {
                                  __proto__: null,