"No newline at end of file" after formatting file in VS Code

[bersbersbers]

1. Create a file bug.R containting this line: styler::style_file("bug.R") (no newline at end of file).
2. Run it using Rscript bug.R
3. Note that a newline at the end of file has been introduced. So this seems to be tidyverse style.
4. Note also that the GitHub web-interface file editor introduces a newline at the end of the file - there is no way to even avoid it.
5. .Rprofile ignores the last line if it does not end in a newline, see https://yihui.org/en/2018/04/rprofile-trailing-newline/

I think the above establishes that a file should end in a newline character.

Now, the R language server seems to remove that newline character - inconsistently!

Note especially how with "editor.formatOnSave": true, it takes me 5 tries to reproduce the problem.

[renkun-ken]

You might want to turn on files.insertFinalNewline in your vscode settings as a quick walk-around.

I'll take a closer look at the document formatting provider then.

[bersbersbers]

Thanks for looking into this! Just know that files.insertFinalNewline inserts an additional newline, which results in a duplicate newline in those cases where the trailing newline was not removed originally. So you either have 0 or 1 newline, OR 1 or 2 newlines - never 1 newline consistently.

[lorenzwalthert]

FWIW: The reason why styler ensures always exactly one trailing empty line (when the input is a file, e.g. not in style_text()) is described here: https://unix.stackexchange.com/questions/18743/whats-the-point-in-adding-a-new-line-to-the-end-of-a-file

[lorenzwalthert]

Other people have experienced this while formatting on save:

• ARROW-13562: [R] Styler followups apache/arrow#10879 (comment)
• Run on change lorenzwalthert/touchstone#41 (comment)

[lorenzwalthert]

This seems to be a major headache for some people. Can we fix it?

[renkun-ken]

Let me take a look into this.

[renkun-ken]

Looks like it is caused by how styler uses cache and how it handles empty line are not consistent.

First, clear the styler cache.

rm -rf ~/.cache/R/R.cache/styler

Then try the following:

> str(styler::style_text(c("print(1)", "")))                                                                        
 'vertical' chr "print(1)"

> str(styler::style_text(c("print(1)", "")))                                                                        
 'vertical' chr [1:2] "print(1)" ""

> str(styler::style_text(c("print(1)", "")))                                                                        
 'vertical' chr [1:2] "print(1)" ""

> str(styler::style_text(c("print(2)", "")))                                                                        
 'vertical' chr "print(2)"

> str(styler::style_text(c("print(2)", "")))                                                                        
 'vertical' chr [1:2] "print(2)" ""

> str(styler::style_text(c("print(2)", "")))                                                                        
 'vertical' chr [1:2] "print(2)" ""

> str(styler::style_text(c("print(3)", "")))                                                                        
 'vertical' chr "print(3)"

> str(styler::style_text(c("print(3)", "")))                                                                        
 'vertical' chr [1:2] "print(3)" ""

> str(styler::style_text(c("print(3)", "")))                                                                        
 'vertical' chr [1:2] "print(3)" ""

Looks like it should be fixed in styler where inconsistent results are returned? @lorenzwalthert

[lorenzwalthert]

Ugh, you are right @renkun-ken. Thanks for looking into it. I will have a look and Open an issue in styler.

[lorenzwalthert]

Seems like it's fixed in dev version of {styler}. Should we just ask people to install the dev version of {styler} or do we need a fix here too? You could check for packageVersion('styler') < '1.6.2.9000 and if that's true, styler:::ensure_last_n_empty(styled_code, n = 1) (or n = 0, not sure how to make sure there is exactly one trailing newline after the formatting is completed). That function exists since {styler} 1.3.2 (released over two years ago).

[lorenzwalthert]

In any case, I think once I release a {styler} update, there should be a minimal version requirement for {styler}.

[renkun-ken]

@lorenzwalthert Do you think #509 should work with both CRAN release and latest dev of styler?

@bersbersbers Does #509 work for you?

[lorenzwalthert]

@nealrichardson @assignUser, with dev styler and dev languageserver, formatting should now be more consistent with regard to trailing blank line. Let us know if it works now for you.

[nealrichardson]

@lorenzwalthert seems to be working for me now--thanks a lot!

[assignUser]

Yep perfect, thanks!

[888Greys]

Thanks a lot. It worked