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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