repl: fix wrong parentheses

lib/internal/repl/utils.js

@@ -301,7 +301,7 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
   function getInputPreview(input, callback) {
     // For similar reasons as `defaultEval`, wrap expressions starting with a
     // curly brace with parenthesis.
-    if (!wrapped && input[0] === '{' && input[input.length - 1] !== ';') {
+    if (!wrapped && input[0] === '{' && input[input.length - 1] !== ';' && isValidSyntax(input)) {
       input = `(${input})`;
       wrapped = true;
     }
@@ -754,6 +754,25 @@ function setupReverseSearch(repl) {
 
 const startsWithBraceRegExp = /^\s*{/;
 const endsWithSemicolonRegExp = /;\s*$/;
+function isValidSyntax(input) {
+  try {
+    AcornParser.parse(input, {
+      ecmaVersion: 'latest',
+      allowAwaitOutsideFunction: true,
+    });
+    return true;
+  } catch {
+    try {
+      AcornParser.parse(`_=${input}`, {
+        ecmaVersion: 'latest',
+        allowAwaitOutsideFunction: true,
+      });
+      return true;
+    } catch {
+      return false;
+    }
+  }
+}
 
 /**
  * Checks if some provided code represents an object literal.
@@ -776,4 +795,5 @@ module.exports = {
   setupPreview,
   setupReverseSearch,
   isObjectLiteral,
+  isValidSyntax,
 };

lib/repl.js

@@ -177,6 +177,7 @@ const {
   setupPreview,
   setupReverseSearch,
   isObjectLiteral,
+  isValidSyntax,
 } = require('internal/repl/utils');
 const {
   constants: {
@@ -445,7 +446,7 @@ function REPLServer(prompt,
     let awaitPromise = false;
     const input = code;
 
-    if (isObjectLiteral(code)) {
+    if (isObjectLiteral(code) && isValidSyntax(code)) {
       // Add parentheses to make sure `code` is parsed as an expression
       code = `(${StringPrototypeTrim(code)})\n`;
       wrappedCmd = true;
@@ -2156,6 +2157,7 @@ module.exports = {
   REPL_MODE_SLOPPY,
   REPL_MODE_STRICT,
   Recoverable,
+  isValidSyntax,
 };
 
 ObjectDefineProperty(module.exports, 'builtinModules', {

test/parallel/test-repl-preview.js

@@ -157,6 +157,83 @@ async function tests(options) {
       '\x1B[90m1\x1B[39m\x1B[12G\x1B[1A\x1B[1B\x1B[2K\x1B[1A\r',
       '\x1B[33m1\x1B[39m',
     ]
+  }, {
+    input: 'aaaa',
+    noPreview: 'Uncaught ReferenceError: aaaa is not defined',
+    preview: [
+      'aaaa\r',
+      'Uncaught ReferenceError: aaaa is not defined',
+    ]
+  }, {
+    input: '/0',
+    noPreview: '/0',
+    preview: [
+      '/0\r',
+      '/0',
+      '^',
+      '',
+      'Uncaught SyntaxError: Invalid regular expression: missing /',
+    ]
+  }, {
+    input: '{})',
+    noPreview: '{})',
+    preview: [
+      '{})\r',
+      '{})',
+      '  ^',
+      '',
+      "Uncaught SyntaxError: Unexpected token ')'",
+    ],
+  }, {
+    input: "{ a: '{' }",
+    noPreview: "{ a: \x1B[32m'{'\x1B[39m }",
+    preview: [
+      "{ a: '{' }\r",
+      "{ a: \x1B[32m'{'\x1B[39m }",
+    ],
+  }, {
+    input: "{'{':0}",
+    noPreview: "{ \x1B[32m'{'\x1B[39m: \x1B[33m0\x1B[39m }",
+    preview: [
+      "{'{':0}",
+      "\x1B[90m{ '{': 0 }\x1B[39m\x1B[15G\x1B[1A\x1B[1B\x1B[2K\x1B[1A\r",
+      "{ \x1B[32m'{'\x1B[39m: \x1B[33m0\x1B[39m }",
+    ],
+  }, {
+    input: '{[Symbol.for("{")]: 0 }',
+    noPreview: '{ \x1B[32mSymbol({)\x1B[39m: \x1B[33m0\x1B[39m }',
+    preview: [
+      '{[Symbol.for("{")]: 0 }\r',
+      '{ \x1B[32mSymbol({)\x1B[39m: \x1B[33m0\x1B[39m }',
+    ],
+  }, {
+    input: '{},{}',
+    noPreview: '{}',
+    preview: [
+      '{},{}',
+      '\x1B[90m{}\x1B[39m\x1B[13G\x1B[1A\x1B[1B\x1B[2K\x1B[1A\r',
+      '{}',
+    ],
+  }, {
+    input: '{} //',
+    noPreview: 'repl > ',
+    preview: [
+      '{} //\r',
+    ],
+  }, {
+    input: '{} //;',
+    noPreview: 'repl > ',
+    preview: [
+      '{} //;\r',
+    ],
+  }, {
+    input: '{throw 0}',
+    noPreview: 'Uncaught \x1B[33m0\x1B[39m',
+    preview: [
+      '{throw 0}',
+      '\x1B[90m0\x1B[39m\x1B[17G\x1B[1A\x1B[1B\x1B[2K\x1B[1A\r',
+      'Uncaught \x1B[33m0\x1B[39m',
+    ],
   }];
 
   const hasPreview = repl.terminal &&
@@ -177,8 +254,13 @@ async function tests(options) {
       assert.deepStrictEqual(lines, preview);
     } else {
       assert.ok(lines[0].includes(noPreview), lines.map(inspect));
-      if (preview.length !== 1 || preview[0] !== `${input}\r`)
-        assert.strictEqual(lines.length, 2);
+      if (preview.length !== 1 || preview[0] !== `${input}\r`) {
+        if (preview[preview.length - 1].includes('Uncaught SyntaxError')) {
+          assert.strictEqual(lines.length, 5);
+        } else {
+          assert.strictEqual(lines.length, 2);
+        }
+      }
     }
   }
 }

test/parallel/test-repl.js

@@ -328,6 +328,19 @@ const errorTests = [
     expect: '[Function (anonymous)]'
   },
   // Multiline object
+  {
+    send: '{}),({}',
+    expect: '| ',
+  },
+  {
+    send: '}',
+    expect: [
+      '{}),({}',
+      kArrow,
+      '',
+      /^Uncaught SyntaxError: /,
+    ]
+  },
   {
     send: '{ a: ',
     expect: '| '