Include comments when constructing functions? about constructive HOT 5 CLOSED

foo <- function(x) {
  # foo
  x
}

library(constructive)

# we have
construct(foo)
#> {constructive} couldn't create code that reproduces perfectly the input
#> ℹ Call `construct_issues()` to inspect the last issues
#> function(x) {
#>   x
#> }

# we can construct with the srcref
construct(foo, opts_function(srcref = TRUE))
#> {constructive} couldn't create code that reproduces perfectly the input
#> ℹ Call `construct_issues()` to inspect the last issues
#> (function(x) {
#>   x
#> }) |>
#>   structure(
#>     srcref = c(1L, 8L, 4L, 1L, 8L, 1L, 1L, 4L) |>
#>       structure(
#>         srcfile = list2env(
#>           list(
#>             fixedNewlines = TRUE,
#>             lines = c("foo <- function(x) {", "  # foo", "  x", "}", ""),
#>             filename = ""
#>           ),
#>           parent = .GlobalEnv
#>         ) |>
#>           structure(class = c("srcfilecopy", "srcfile")),
#>         class = "srcref"
#>       )
#>   )

# and we can verify that it prints properly
(function(x) {
  x
}) |>
  structure(
    srcref = c(1L, 8L, 4L, 1L, 8L, 1L, 1L, 4L) |>
      structure(
        srcfile = list2env(
          list(
            fixedNewlines = TRUE,
            lines = c("foo <- function(x) {", "  # foo", "  x", "}", ""),
            filename = ""
          ),
          parent = .GlobalEnv
        ) |>
          structure(class = c("srcfilecopy", "srcfile")),
        class = "srcref"
      )
  )
#> function(x) {
#>   # foo
#>   x
#> }

# but the compact and proper way would be to reproduce the idiomatic definition with the comments and get:
function(x) {
  # foo
  x
}

# then I think we just need, though to be safe we should parse it and check that get the same language tree
as.character(attr(foo, "srcref"))
#> [1] "function(x) {" "  # foo"       "  x"           "}"

# This is only for the `opts_function("function")` (the default), for `as.function()` for instance we lose the 
# comments so we cannot use this shortcut to set the secret
as.function(alist(x=, {
  # foo
  x
}))
#> function (x) 
#> {
#>     x
#> }

# For language objects We need `opts_language(srcref=)` because now we cannot faithfully reconstruct the body in isolation
construct(body(foo))
#> quote({
#>   x
#> })
attributes(body(foo))
#> $srcref
#> $srcref[[1]]
#> {
#> 
#> $srcref[[2]]
#> x
#> 
#> 
#> $srcfile
#> <text> 
#> 
#> $wholeSrcref
#> foo <- function(x) {
#>   # foo
#>   x
#> }

# however for that case we cannot reproduce the srcref without setting attributes, because the srcref
# either doesn't reproduce the object, as above, or contains too much, as below
bar <- identity(quote({
  # foo
  x
}))

attributes(bar)
#> $srcref
#> $srcref[[1]]
#> {
#> 
#> $srcref[[2]]
#> x
#> 
#> 
#> $srcfile
#> <text> 
#> 
#> $wholeSrcref
#> bar <- identity(quote({
#>   # foo
#>   x
#> }
as.character(attr(bar, "wholeSrcref"))
#> [1] "bar <- identity(quote({" "  # foo"                
#> [3] "  x"                     "}"

x <- function(x) {
  # foo
  x
}

constructive::construct(x)
#> function(x) {
#>   # foo
#>   x
#> }
constructive::construct(list(a= x))
#> list(
#>   a = function(x) {
#>     # foo
#>     x
#>   }
#> )