parse_all() fails with line directives

[ArcadeAntics]

I had a piece of code from a file, something like:

#line 11
LINENO()

where LINENO is a function I made that returns the line number of the executing expression in the executing script, and #line 11 is a line directive to indicate that the text is originally written starting on line 11 of the script. It erroneously returns something like this:

> evaluate:::parse_all(c("#line 11", "   LINENO()"))
             src     expr
1     #line 11\n         
2     LINENO()\n         
3           NA\n         
4           NA\n         
5           NA\n         
6           NA\n         
7           NA\n         
8           NA\n         
9           NA\n         
10          NA\n         
11            NA LINENO()
> 

I believe this is because evaluate:::parse_all.character does something like this:

    srcref <- attr(exprs, "srcref", exact = TRUE)
    pos <- do.call(rbind, lapply(srcref, unclass))[, c(1, 3), 
        drop = FALSE]

using the first_line and last_line of the srcref (which respects line directives) instead of the first_parsed and last_parsed (which just count lines). I think this error is easily solved by changing c(1, 3) to c(7, 8):

> x <- c("#line 11", "LINENO()")
> parse_all.character2 <- evaluate:::parse_all.character
> body(parse_all.character2)[[c(12, 3, 4)]]
c(1, 3)
> body(parse_all.character2)[[c(12, 3, 4)]] <- quote(c(7, 8))
> evaluate:::parse_all.character(x)
          src     expr
1  #line 11\n         
2  LINENO()\n         
3        NA\n         
4        NA\n         
5        NA\n         
6        NA\n         
7        NA\n         
8        NA\n         
9        NA\n         
10       NA\n         
11         NA LINENO()
>            parse_all.character2(x)
         src     expr
1 #line 11\n         
2   LINENO() LINENO()
> 

I took these details from the doc page ?srcfile. If you need any more details, I'm happy to oblige. Thank you!

[yihui]

Thank you so much! This is absolutely helpful and might take me a long time to figure out (I haven't touched this part of code for several years).