how to split the parameters into different lines and keep them aligned?

[fyears]

After using "format code" in the latest RStudio, the parameters of functions are split into different lines and kept aligned.

But I am unable to find the corresponding settings in formatR package. How to do it with formatR?

Consider the source code:

my_sum = function(a = 1, b = 2, c =3) {
  return(a + b + c)
}

The desired formatted result (RStudio returns this):

my_sum = function(a = 1,
                  b = 2,
                  c = 3) {
  return(a + b + c)
}

[yihui]

formatR cannot do that...

---

Reminder to self: update this post when this feature is implemented.

[jfiksel]

I second adding this feature if possible, since this is the correct way to write functions with multi-line parameters

[yihui]

I wouldn't say "it is the correct way", but it is definitely a favorable style to many people.

I don't feel the implementation is easy, so I'll leave this task to contributors...

[fyears]

I checked out the potential solutions before. It was definitely harder than I think: a basic parser understanding R syntax is needed, rather than any "text processing" logics...

[yihui]

Exactly. You cannot do this only through regular expressions or any text processing techniques. A parser has to be involved.

[jfiksel]

Hm, that sounds way above what I would be capable of doing. It seems that RStudio already implements this, but I am only asking because I have been trying to write R code in Atom for a project that I have to use a remote cluster for. It seems that the atom-beautify package implements formatR for formatting R code

[yihui]

If someone can figure out the RStudio magic, and it turns out not be super difficult to implement in pure R, I'd welcome a pull request. Personally I don't have time or enough interest in this feature.

[naught101]

It's this basically a duplicate of #53?

[yihui]

@naught101 Yes.

I can tell you that RStudio actually uses JavaScript to reformat the R code, so the magic cannot be directly ported to formatR.