repl: show lexically scoped vars in tab completion

Use the V8 inspector protocol, if available, to query the list of lexically scoped variables (defined with `let`, `const` or `class`). PR-URL: #16591 Fixes: #983 Reviewed-By: Timothy Gu <timothygu99@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: targos

lib/internal/util/inspector.js

@@ -0,0 +1,25 @@
+'use strict';
+
+const hasInspector = process.config.variables.v8_enable_inspector === 1;
+const inspector = hasInspector ? require('inspector') : undefined;
+
+let session;
+
+function sendInspectorCommand(cb, onError) {
+ if (!hasInspector) return onError();
+ if (session === undefined) session = new inspector.Session();
+ try {
+ session.connect();
+ try {
+ return cb(session);
+ } finally {
+ session.disconnect();
+ }
+ } catch (e) {
+ return onError();
+ }
+}
+
+module.exports = {
+ sendInspectorCommand
+};

lib/repl.js

@@ -58,6 +58,7 @@ const Module = require('module');
 const domain = require('domain');
 const debug = util.debuglog('repl');
 const errors = require('internal/errors');
+const { sendInspectorCommand } = require('internal/util/inspector');
 
 const parentModule = module;
 const replMap = new WeakMap();
@@ -75,6 +76,7 @@ for (var n = 0; n < GLOBAL_OBJECT_PROPERTIES.length; n++) {
  GLOBAL_OBJECT_PROPERTIES[n];
 }
 const kBufferedCommandSymbol = Symbol('bufferedCommand');
+const kContextId = Symbol('contextId');
 
 try {
  // hack for require.resolve("./relative") to work properly.
@@ -155,6 +157,8 @@ function REPLServer(prompt,
  self.last = undefined;
  self.breakEvalOnSigint = !!breakEvalOnSigint;
  self.editorMode = false;
+ // Context id for use with the inspector protocol.
+ self[kContextId] = undefined;
 
  // just for backwards compat, see github.com/joyent/node/pull/7127
  self.rli = this;
@@ -644,7 +648,16 @@ REPLServer.prototype.createContext = function() {
  if (this.useGlobal) {
  context = global;
  } else {
- context = vm.createContext();
+ sendInspectorCommand((session) => {
+ session.post('Runtime.enable');
+ session.on('Runtime.executionContextCreated', ({ params }) => {
+ this[kContextId] = params.context.id;
+ });
+ context = vm.createContext();
+ session.post('Runtime.disable');
+ }, () => {
+ context = vm.createContext();
+ });
  context.global = context;
  const _console = new Console(this.outputStream);
  Object.defineProperty(context, 'console', {
@@ -779,6 +792,18 @@ function filteredOwnPropertyNames(obj) {
  return Object.getOwnPropertyNames(obj).filter(intFilter);
 }
 
+function getGlobalLexicalScopeNames(contextId) {
+ return sendInspectorCommand((session) => {
+ let names = [];
+ session.post('Runtime.globalLexicalScopeNames', {
+ executionContextId: contextId
+ }, (error, result) => {
+ if (!error) names = result.names;
+ });
+ return names;
+ }, () => []);
+}
+
 REPLServer.prototype.complete = function() {
  this.completer.apply(this, arguments);
 };
@@ -942,6 +967,7 @@ function complete(line, callback) {
  // If context is instance of vm.ScriptContext
  // Get global vars synchronously
  if (this.useGlobal || vm.isContext(this.context)) {
+ completionGroups.push(getGlobalLexicalScopeNames(this[kContextId]));
  var contextProto = this.context;
  while (contextProto = Object.getPrototypeOf(contextProto)) {
  completionGroups.push(

node.gyp

@@ -127,6 +127,7 @@
  'lib/internal/url.js',
  'lib/internal/util.js',
  'lib/internal/util/comparisons.js',
+ 'lib/internal/util/inspector.js',
  'lib/internal/util/types.js',
  'lib/internal/http2/core.js',
  'lib/internal/http2/compat.js',

test/parallel/test-repl-inspector.js

@@ -0,0 +1,34 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const repl = require('repl');
+
+common.skipIfInspectorDisabled();
+
+// This test verifies that the V8 inspector API is usable in the REPL.
+
+const putIn = new common.ArrayStream();
+let output = '';
+putIn.write = function(data) {
+ output += data;
+};
+
+const testMe = repl.start('', putIn);
+
+putIn.run(['const myVariable = 42']);
+
+testMe.complete('myVar', common.mustCall((error, data) => {
+ assert.deepStrictEqual(data, [['myVariable'], 'myVar']);
+}));
+
+putIn.run([
+ 'const inspector = require("inspector")',
+ 'const session = new inspector.Session()',
+ 'session.connect()',
+ 'session.post("Runtime.evaluate", { expression: "1 + 1" }, console.log)',
+ 'session.disconnect()'
+]);
+
+assert(output.includes(
+ "null { result: { type: 'number', value: 2, description: '2' } }"));

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

@@ -24,6 +24,7 @@
 const common = require('../common');
 const assert = require('assert');
 const fixtures = require('../common/fixtures');
+const hasInspector = process.config.variables.v8_enable_inspector === 1;
 
 // We have to change the directory to ../fixtures before requiring repl
 // in order to make the tests for completion of node_modules work properly
@@ -529,3 +530,23 @@ editorStream.run(['.editor']);
 editor.completer('var log = console.l', common.mustCall((error, data) => {
  assert.deepStrictEqual(data, [['console.log'], 'console.l']);
 }));
+
+{
+ // tab completion of lexically scoped variables
+ const stream = new common.ArrayStream();
+ const testRepl = repl.start({ stream });
+
+ stream.run([`
+ let lexicalLet = true;
+ const lexicalConst = true;
+ class lexicalKlass {}
+ `]);
+
+ ['Let', 'Const', 'Klass'].forEach((type) => {
+ const query = `lexical${type[0]}`;
+ const expected = hasInspector ? [[`lexical${type}`], query] : [];
+ testRepl.complete(query, common.mustCall((error, data) => {
+ assert.deepStrictEqual(data, expected);
+ }));
+ });
+}