R devel - Jun 2013 - sys.source() does not provide the parsing info to eval()

Hello,

It seems that the parsing information attached to expressions parsed by the
parse() function when keep.source=TRUE is not provided to the eval()
function.

Please consider this code:

path <- tempfile()
code <- '(function() print( str( sys.calls() ) ))()'
writeLines(code, path)
sys.source(path, envir=globalenv(), keep.source=TRUE)
> OUTPUT:
Dotted pair list of 4
 $ : language sys.source(path, envir = globalenv(), keep.source = TRUE)
 $ : language eval(i, envir)
 $ : language eval(expr, envir, enclos)
 $ : language (function() print(str(sys.calls())))()
NULL

then:
eval(parse(text=code))
> OUTPUT:
Dotted pair list of 3
 $ : language eval(parse(text = code))
 $ : language eval(expr, envir, enclos)
 $ :length 1 (function() print(str(sys.calls())))()
  ..- attr(*, "srcref")=Class 'srcref'  atomic [1:8] 1 1 1 42
1 42 1 1
  .. .. ..- attr(*, "srcfile")=Classes 'srcfilecopy',
'srcfile'
<environment: 0x7f42951fc388>

As you can see, when using eval() directly, the expression/call has the
parsing information available in the "srcref" attribute, but not when
using
sys.source()

Looking at sys.source() implementation, this seems to be caused by this
line:
for (i in exprs) eval(i, envir)

The attribute "srcref" is not available anymore when "exprs"
is subsetted,
as illustred by the code below:

ex <- parse( text="1+1; 2+2")

attr(ex, 'srcref')
print(str(ex))
# length 2 expression(1 + 1, 2 + 2)
#  - attr(*, "srcref")=List of 2
#   ..$ :Class 'srcref'  atomic [1:8] 1 1 1 3 1 3 1 1
#   .. .. ..- attr(*, "srcfile")=Classes 'srcfilecopy',
'srcfile'
<environment: 0x7f42951f3b00>
#   ..$ :Class 'srcref'  atomic [1:8] 1 6 1 8 6 8 1 1
#   .. .. ..- attr(*, "srcfile")=Classes 'srcfilecopy',
'srcfile'
<environment: 0x7f42951f3b00>
#  - attr(*, "srcfile")=Classes 'srcfilecopy',
'srcfile' <environment:
0x7f42951f3b00>
#  - attr(*, "wholeSrcref")=Class 'srcref'  atomic [1:8] 1 0 2
0 0 0 1 2
#   .. ..- attr(*, "srcfile")=Classes 'srcfilecopy',
'srcfile'
<environment: 0x7f42951f3b00>
# NULL

print( str(ex[[1]]))
#  language 1 + 1
# NULL

print( str(ex[1]))
# length 1 expression(1 + 1)
#  - attr(*, "srcref")=List of 1
#   ..$ :Class 'srcref'  atomic [1:8] 1 1 1 3 1 3 1 1
#   .. .. ..- attr(*, "srcfile")=Classes 'srcfilecopy',
'srcfile'
<environment: 0x7f42951f3b00>
# NULL


I suppose that the line "for (i in exprs) eval(i, envir)" could be
replaced
by "eval(exprs, envir)" ?

Best,

Karl Forner



P.S
> sessionInfo()
R version 3.0.1 (2013-05-16)
Platform: x86_64-unknown-linux-gnu (64-bit)
...

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