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REPL bug fixes

Rodrigo Muino Tomonari requested to merge github/fork/thefourtheye/repl-bug-fixes into master

There are four bug fixes.

1. Better line continuation feature

As it is, REPL doesn't honour the line continuation feature very well. This patch

  1. keeps track of the beginning of the string literals and if they don't end or current line doesn't end with line continuation, then error out.
  2. monitors if the line continuation character is used without the string literal and errors out if that happens.

2. Removing undefined when unknown REPL command is used

When an invalid REPL keyword is used, we actually print undefined as well in the console.

> process.version
'v2.3.4'
> .invalid_repl_command
Invalid REPL keyword
undefined
>

This patch prevents printing undefined in this case.

> process.version
'v2.3.5-pre'
> .invalid_repl_command
Invalid REPL keyword

3. preventing REPL crash with inherited properties

When an inherited property is used as a REPL keyword, the REPL crashes.

➜  Desktop  iojs
> process.version
'v2.3.4'
> .toString
readline.js:913
        stream[ESCAPE_DECODER].next(r[i]);
                                ^
TypeError: Cannot read property 'call' of undefined
    at REPLServer.parseREPLKeyword (repl.js:746:15)
    at REPLServer.<anonymous> (repl.js:284:16)
    at emitOne (events.js:77:13)
    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)
    at ReadStream.onkeypress (readline.js:105:10)
    at emitTwo (events.js:87:13)
    at ReadStream.emit (events.js:172:7)
➜  Desktop

This patch makes the internal commands object inherit from null so that there will be no inherited properties.

> process.version
'v2.3.5-pre'
> .toString
Invalid REPL keyword
>

4. Better empty line handling

In REPL, if we try to evaluate an empty line, we get undefined.

> process.version
'v2.3.4'
>
undefined
>
undefined
>

This patch prevents undefined from printing if the string is empty.

> process.version
'v2.3.5-pre'
>
>
>

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