R devel - Jan 2012 - parse( connection) and source-keeping

In R <= 2.13.x, calling 'parse( con)' where 'con' is a
connection, 'options( keep.source)' is TRUE,  and default
'srcfile' would preserve the source. In R >= 2.14.1, it doesn't.
> tf <- tempfile()
> options( keep.source=TRUE)
> texto <- c( 'function() { # comment', '}')
> parse( text=texto)
expression(function() { # comment
})
> cat( texto, file=tf, sep='\n')
> parse( file=tf)
expression(function() { # comment
})
> parse( file( tf))
expression(function() {
})
> parse( textConnection( texto))
expression(function() {
})

and yes I didn't bother closing any connections.

My suspicion is that this change is unintentional, and it seems to me that the
best option would be for 'connection' to work like 'text' does
here, ie to attach a 'srcfilecopy' containing the contents.

I didn't submit a bug report because the documentation (which hasn't
changed in this respect) actually doesn't say what 'parse' should do
with 'connection' (as opposed to 'text' or 'file')
argument when 'getOption( keep.source)' is TRUE and 'srcfile' is
NULL. [BTW it's also unstated which argument takes precedence if a
non-default 'srcfile' argument is specified.] So some additional
explanation is needed there at a minimum, but also a decision as to what the
best behaviour would be.

bye
Mark

Mark Bravington
CSIRO CMIS
Marine Lab
Hobart
Australia

On 12-01-11 3:54 PM, Mark.Bravington at csiro.au wrote:
> In R<= 2.13.x, calling 'parse( con)' where 'con' is a
connection, 'options( keep.source)' is TRUE,  and default
'srcfile' would preserve the source. In R>= 2.14.1, it doesn't.
Actually, it preserved the "source" attribute of the function if it 
could, but didn't add a srcref.  Sometimes it would fail, giving a 
message like

Error in parse(textConnection(texto)) :
   function is too long to keep source (at line 8812)

>
>> tf<- tempfile()
>> options( keep.source=TRUE)
>> texto<- c( 'function() { # comment', '}')
>> parse( text=texto)
> expression(function() { # comment
> })
>> cat( texto, file=tf, sep='\n')
>> parse( file=tf)
> expression(function() { # comment
> })
>> parse( file( tf))
> expression(function() {
> })
>> parse( textConnection( texto))
> expression(function() {
> })
>
> and yes I didn't bother closing any connections.
>
> My suspicion is that this change is unintentional, and it seems to me that
the best option would be for 'connection' to work like 'text'
does here, ie to attach a 'srcfilecopy' containing the contents.
Yes, that does sound like a good idea.

Duncan Murdoch
> I didn't submit a bug report because the documentation (which
hasn't changed in this respect) actually doesn't say what
'parse' should do with 'connection' (as opposed to
'text' or 'file') argument when 'getOption(
keep.source)' is TRUE and 'srcfile' is NULL. [BTW it's also
unstated which argument takes precedence if a non-default 'srcfile'
argument is specified.] So some additional explanation is needed there at a
minimum, but also a decision as to what the best behaviour would be.
>
> bye
> Mark
>
> Mark Bravington
> CSIRO CMIS
> Marine Lab
> Hobart
> Australia
>
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