toJSON is not encoding control characters

[fernandoacorreia]

The JSON specification does not allow control characters in strings. toJSON is not escaping these characters:

$ R --vanilla

R version 3.1.2 (2014-10-31) -- "Pumpkin Helmet"
Copyright (C) 2014 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

  Natural language support but running in an English locale

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> library(RJSONIO)
> library(rjson)

Attaching package: ‘rjson’

The following objects are masked from ‘package:RJSONIO’:

    fromJSON, toJSON

> sessionInfo()
R version 3.1.2 (2014-10-31)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=pt_BR.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=pt_BR.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=pt_BR.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=pt_BR.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] rjson_0.2.15  RJSONIO_1.3-0
> x <- intToUtf8(27)
> x
[1] "\033"
> RJSONIO::toJSON(x)
[1] "[ \"\033\" ]"
> rjson::toJSON(x)
[1] "\"\\u001b\""

When deserializing with another library such as Java's Jackson, this results in deserialization errors:

org.codehaus.jackson.JsonParseException: Illegal unquoted character ((CTRL-CHAR, code 27)): has to be escaped using backslash to be included in string value