Get or set function body

fn_body() is a simple wrapper around base::body(). It always returns a { expression and throws an error when the input is a primitive function (whereas body() returns NULL). The setter version preserves attributes, unlike body<-.

fn_body(fn = caller_fn())

fn_body(fn) <- value

Arguments

fn	A function. It is lookep up in the calling frame if not supplied.
value	New formals or formals names for fn.

Examples

# fn_body() is like body() but always returns a block:
fn <- function() do()
body(fn)
#> do()
fn_body(fn)
#> {
#>     do()
#> }

# It also throws an error when used on a primitive function:
try(fn_body(base::list))
#> Error : `fn` is not a closure
#> Backtrace:
#>      █
#>   1. ├─base::tryCatch(...)
#>   2. │ └─base:::tryCatchList(expr, classes, parentenv, handlers)
#>   3. │   ├─base:::tryCatchOne(...)
#>   4. │   │ └─base:::doTryCatch(return(expr), name, parentenv, handler)
#>   5. │   └─base:::tryCatchList(expr, names[-nh], parentenv, handlers[-nh])
#>   6. │     └─base:::tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>   7. │       └─base:::doTryCatch(return(expr), name, parentenv, handler)
#>   8. ├─base::withCallingHandlers(...)
#>   9. ├─base::saveRDS(...)
#>  10. ├─base::do.call(...)
#>  11. ├─(function (what, args, quote = FALSE, envir = parent.frame()) ...
#>  12. └─(function (..., crayon_enabled, crayon_colors, pkgdown_internet) ...
#>  13.   └─pkgdown::build_site(...)
#>  14.     └─pkgdown:::build_site_local(...)
#>  15.       └─pkgdown::build_reference(...)
#>  16.         └─purrr::map(...)
#>  17.           └─pkgdown:::.f(.x[[i]], ...)
#>  18.             └─pkgdown:::data_reference_topic(...)
#>  19.               ├─pkgdown:::as_data(...)
#>  20.               └─pkgdown:::as_data.tag_examples(...)
#>  21.                 └─purrr::pmap_chr(...)
#>  22.                   └─pkgdown:::.f(...)
#>  23.                     ├─withr::with_options(...)
#>  24.                     │ └─base::force(code)
#>  25.                     └─evaluate::evaluate(code, env, new_device = TRUE)
#>  26.                       └─evaluate:::evaluate_call(...)
#>  27.                         ├─evaluate:::timing_fn(...)
#>  28.                         ├─evaluate:::handle(...)
#>  29.                         │ └─base::try(f, silent = TRUE)
#>  30.                         │   └─base::tryCatch(...)
#>  31.                         │     └─base:::tryCatchList(expr, classes, parentenv, handlers)
#>  32.                         │       └─base:::tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>  33.                         │         └─base:::doTryCatch(return(expr), name, parentenv, handler)
#>  34.                         ├─base::withCallingHandlers(...)
#>  35.                         ├─base::withVisible(eval(expr, envir, enclos))
#>  36.                         └─base::eval(expr, envir, enclos)
#>  37.                           └─base::eval(expr, envir, enclos)
#>  38.                             ├─base::try(fn_body(base::list))
#>  39.                             │ └─base::tryCatch(...)
#>  40.                             │   └─base:::tryCatchList(expr, classes, parentenv, handlers)
#>  41.                             │     └─base:::tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>  42.                             │       └─base:::doTryCatch(return(expr), name, parentenv, handler)
#>  43.                             └─rlang::fn_body(base::list)