Tweak long argument advice

[lorenzwalthert]

This addresses https://github.com/tidyverse/style/issues/173 (and https://github.com/r-lib/styler/issues/829) I think. I must say I am quite surprised to see this proposed by @hadley. I can't really follow the rationale of introducing double indention to the style guide, there is no such thing so far AFAIK in this style guide.

~I think it's quite a fundamental change, requiring adaption for {styler}, {lintr} as well as IDEs such as RStudio or vs code language server to give the expected indention on ENTER. Is this already set in stone? As one can probably guess, I am not really in favor of that change 😄 , but it's obviously not up to me to decide on it...~

Ok maybe I am just too used to the old style and worked too many hours to implement this in {styler} to have a helpful opinion on that... haha. Adaption requirments for IDEs and {styler} and {lintr} are still relevant though.

[hadley]

I opened this to kick off internal discussion.

[lorenzwalthert]

Ok, thanks for explaining.

[luciorq]

The definition of each argument in its line is also more suitable for tracking changes in version control.

It is indeed about time to have it addressed somewhere in the R ecosystem.

But, what is the rationale for double indent? There is any language or style guide that already uses it? I haven't stumbled upon it before.

[hadley]

Now that we've discussed it internally and I've made some changes to my original proposal, it's now worth looking at @lorenzwalthert. The double indentation is inspired by Google's style guide for C++.

[hadley]

https://github.com/rstudio/rstudio/pull/9766 adds IDE support

[hadley]

Would love to get your feedback on this before Sept 3 (one week) so we can make a decision on whether or not to move forward.

[MichaelChirico]

LGTM cc @michaelquinn32

[michaelquinn32]

LGTM. Thanks to everyone that worked on this.

We've got some really gnarly long names lurking in our codebase, and I am very happy to say goodbye the ugly hacks we've had to implement to get them formatted correctly. I think this also goes a long way towards addressing some other internal concerns, like how long names with parentheses-aligned arguments produce a lot of whitespace between the function name and the body of the code.

[lorenzwalthert]

Thanks for adding context (Google C++ style guide), it makes more sense now. I am ok with this, but I don't think it's necessary to always use double indention. If you can make all lines less than 80 characters with the existing rule, I think this is fine:

# all lines less than 80 characters
long_function_name <- function(a = "a long argument",
                               b = "another argument",
                               c = "another long argument") {
  # As usual code is indented by two spaces.
  ...
}

As I understand, the primary case you want to tackle is this:

# some lines longer than 80 characters
long_function_name_that_makes_at_least_one_arg_over_80_characters <- function(a = "a long argument",
                                                                              b = "another argument", 
                                                                              c = "another long argument") {
  # As usual code is indented by two spaces.
  ...
}

Then, proposed re-arrangement makes most sense.

long_function_name_that_makes_at_least_one_arg_over_80_characters <- function(
    a = "a long argument",
    b = "another argument", 
    c = "another long argument") {
  # As usual code is indented by two spaces.
  ...
}

[hadley]

@lorenzwalthert I don't consider the style guide to be binding; it's just a suggestion. I think it's better to keep the guide as short and prescriptive as possible, recognising that anyone is free to deviate it from it at any time for any reason.

[lorenzwalthert]

Ok. I see that we can’t specify all cases here and that it is for the reader’s convenience we keep it brief. In general, I consider this style guide to be binding for {styler} tough, so I plan to implement whatever we decide in this issue for the sake of consistency (even if I did not agree with everything 😊).

[hadley]

@lorenzwalthert in that case, I think it's better to be consistent and always indent function args by four spaces — it's a simpler rule, thus easier to remember. (Assuming that they don't all fit on one line)

[hadley]

@lorenzwalthert you and @lionel- have convinced me that I was being too restrictive, and I've reworded to allow either function-indent or double-indent style (preferring function-indent when it fits).

To make it easier to switch between the different types, @lionel- is going to work on an add-in that can easily toggle between the different styles, and if you're interested, he'll add it to styler.

[lorenzwalthert]

Ok, yes, in principle interested, we have to see how we can handle this in {styler}, what the default should be and how it plays with IDEs like RStudio.