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Standalone blocks don't work in node REPL console  #5576

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Standalone blocks don't work in node REPL console #5576
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confirmed-bugIssues and PRs for confirmed bugs.replIssues and PRs related to the REPL subsystem.

Description

@polybuildr
polybuildr
opened on Mar 6, 2016

Standalone blocks don't play well with the node console.

{ var x = 4; console.log(x); }

works fine when put in a file and run, but when run in the console,

SyntaxError: Unexpected identifier
    at Object.exports.createScript (vm.js:24:10)
    at REPLServer.defaultEval (repl.js:137:25)
    at bound (domain.js:250:14)
    at REPLServer.runBound [as eval] (domain.js:263:12)
    at REPLServer.<anonymous> (repl.js:393:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:210:10)
    at REPLServer.Interface._line (readline.js:549:8)
    at REPLServer.Interface._ttyWrite (readline.js:826:14)
  • Version: v4.1.1
  • Platform: Linux matrix 3.13.0-79-generic #123-Ubuntu SMP Fri Feb 19 14:27:58 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Activity

  1. mscdex
    added
    replIssues and PRs related to the REPL subsystem.
    confirmed-bugIssues and PRs for confirmed bugs.
    on Mar 6, 2016

  2. bnoordhuis commented on Mar 6, 2016

    @bnoordhuis
    bnoordhuis
    on Mar 6, 2016
    Member

    The REPL wraps input in parentheses, otherwise {} would be interpreted as an empty statement instead of an object literal (which is what most people expect - the evaluator was changed years ago after receiving many, many bug reports about that.)

    You can see it for yourself when you run the REPL with NODE_DEBUG=repl set in the environment:

    $ env NODE_DEBUG=repl out/Release/node 
> { x: 42 }
REPL 5133: line "{ x: 42 }"
REPL 5133: eval "({ x: 42 })\n"
REPL 5133: finish undefined { x: 42 }
{ x: 42 }

> { var x = 4; console.log(x); }
REPL 5133: line "{ var x = 4; console.log(x); }"
REPL 5133: eval "({ var x = 4; console.log(x); })\n"
REPL 5133: parse error "({ var x = 4; console.log(x); })\n" SyntaxError: Unexpected identifier
<elided>

    A possible solution is to retry without parens on SyntaxError but there are some inputs that are ambiguous either way, e.g., { x } can either be a block statement evaluating to x or an ES6 object literal with an x property.

  3. princejwesley commented on Mar 7, 2016

    @princejwesley
    princejwesley
    on Mar 7, 2016
    Contributor

    Same behaviour in chrome console (wrapped with parenthesis).
    image

  4. princejwesley commented on Mar 7, 2016

    @princejwesley
    princejwesley
    on Mar 7, 2016
    Contributor

    @bnoordhuis see #5581

  5. jasnell
    closed this as completedin a38d6adon Mar 19, 2016
  6. evanlucas
    added 2 commits that reference this issue on Mar 30, 2016

    repl: support standalone blocks

    58de768

    repl: support standalone blocks

    4271732
  7. sjarmak
    added a commit that references this issue on Jul 27, 2026

    repl: support standalone blocks

    a38d6ad
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