R_parseVector and syntax error [was: error messages while parsing with rniParse]

Duncan Murdoch wrote:
  

Simon Urbanek wrote:
    

On Jun 18, 2009, at 17:02 , Duncan Murdoch wrote:
 
      

Romain Francois wrote:
   
        

Hello,

[I'm redirecting this here from stats-rosuda-devel]

When parsing R code through R_parseVector and the code generates 
an  error (syntax error), is there a way to grab the error.
It looks like yyerror populates the buffer "R_ParseErrorMsg", but  
then the variable is not part of the public api.

Would it be possible to add yet another entry point to the parser  
that would basically wrap R_parseVector so that it would have an  
extra char* argument that would bring back the error message if  
there is an error?


      
          

I would oppose that.  Suggest ways to reduce the complexity of the  
parser interface and I'd be interested.  It's a nightmare to make  
any changes there.

You can always call the R function wrapped in try(), so it's not as  
though this would give you anything that you don't already have  
access to.
    
        

I'm not quite following - we're talking about R_ParseVector in C 
code  so the point is that the C code gets access to the error 
message so it  can relay it to the user. 
      

I understood that.  But the C code can get the error message by 
evaluating an R expression and looking at the result.

    

There are no R-level functions involved  here. The issue here for the 
moment is that this information is  retrievable at R level but not 
(officially) at the C level. 
      

I wouldn't mind exposing the underlying information in a clean way, 
but the string in R_ParseVector isn't all a front end should get.
    

Great. Let's do that.
Is a function that simply returns some of the static variables used by 
bison clean enough ?
  

At the time of an R_ParseVector syntax error, the parser knows what 
token it couldn't handle, and it knows its classification, and the 
location in the file where it came from.   Not all of that makes it 
through to the error message.
    

As for  reducing complexity - technically, there is no complexity 
added since  all this is already in place ... [adding extra char * 
argument to  ParseVector may not be the best way but that's not what 
I'm arguing  for].   
      

It was what I was arguing against.

Duncan Murdoch

    

Or am I missing something?
      
Cheers,
S


 
      

Romain

Simon Urbanek wrote:

     
          

On Jun 15, 2009, at 12:05 , Romain Francois wrote:


       
            

Hello,

In JRI, is there a way to get the error message that is 
generated  by the
parser through rniParse
For example, if I have this :

long y = re.rniParse( "rnorm( 10 ))", 1 ) ;

this obviously generates a parse error, so y will be the same as
(R_NilValue) :

long null_id = re.rniEval( re.rniParse( "NULL", 1 ), 0 ) ;

I guess the underlying question is : "Is R_ParseErrorMsg exposed to
JRI".

          
              

AFAICT R_ParseErrorMsg and friends are not exposed by the R API -  
they are not accessible outside, so they cannot be use by JRI. It  
would be nice if there was a way of accessing that info, but R  
doesn't currently support that.

Cheers,
Simon


       
            

The reason is I would like to bring back the message as part of an
exception generated when the code does not parse.

Romain