Feature: capture parsing errors

[carloscinelli]

Related question on SO: http://stackoverflow.com/questions/35842682/knitr-knitting-chunks-with-parsing-errors

Maybe it would be a good idea to capture parsing errors. For instance, the code below:

f <- function(x){
  z <- sum(x
           #
           y <- x + 1
           return(x + y + z)
}

Should give 3 errors:

> Sys.setenv(LANG = "en")
> f <- function(x){
+   z <- sum(x
+            #
+            y <- x + 1
Error: unexpected symbol in:
"           #
           y"
>            return(x + y + z)
Error: object 'y' not found
> }
Error: unexpected '}' in "}"

The current version of the evaluate() function stops at the first error:

text <- "f <- function(x){
  z <- sum(x
#
y <- x + 1
return(x + y + z)
}"
evaluate(text)
Error in parse(text = x, srcfile = src) : <text>:4:1: unexpected symbol
3: #
4: y
   ^

The main use case I am thinking here is for educational material (which is what I am working on now), but maybe there will be other use cases too.