-----Original Message-----
From: Duncan Murdoch [mailto:murdoch.duncan at gmail.com]
Sent: Friday, September 02, 2011 4:58 AM
To: William Dunlap
Cc: r-devel at r-project.org
Subject: Re: [Rd] parser does not catch strings without closing quote
On 11-09-01 6:24 PM, William Dunlap wrote:
Shouldn't the parser complain about unfinished strings in files?
It doesn't and will tack on a newline if there isn't one there.
> withOption<- function(optionList, expr) {
+ oldOption<- options(optionList)
+ on.exit(options(oldOption))
+ expr
+ }
> cat(file=tf<-tempfile(), "\"string without closing quote\n")
> p<- withOption(list(keep.source=FALSE), parse(tf))
> p
expression("string without closing quote\n")
> cat(file=tf<-tempfile(), "\"string with no closing quote nor newline")
> p<- withOption(list(keep.source=FALSE), parse(tf))
> p
expression("string with no closing quote nor newline\n")
It does complain when parsing a character string with the same problem.
> p<- withOption(list(keep.source=FALSE), parse(text="\"unfinished string"))
Error in parse(text = "\"unfinished string") :
2:0: unexpected end of input
1: "unfinished string
^
I assume this is a bug, but the way the parser handles input is quite a
mess, so I'm not sure where to fix this. The obvious place (within the
parser where it is getting tokens) does not work: the higher level code
breaks up input into small pieces, and the parser frequently hits the
end of a piece (at a newline or semicolon, for example), and signals an
incomplete parse, which is restarted.
(For others than Bill: this is necessary because the S language doesn't
have a clear end of statement marker. If the parser sees "x + ", it
tries to get more input to finish the statement. It's only an error if
nothing more is there.)
A possibility would be to add a new token "incomplete string", which
will eventually trigger an error if the restart doesn't complete it.
I'll think about it...
Duncan Murdoch