R 4.2: Support new pipe placeholder syntax

[cderv]

Coming to R 4.2 is the new pipe with now a placeholder syntax

New pipe support has been added in

• support lambda, pipe in upcoming r-devel #8533
• support pipe-bind syntax in R-devel #8744

Now you can also use a paceholder

mtcars |> subset(cyl == 4) |> lm(mpg ~ disp, data = _)

Example here: https://twitter.com/henrikbengtsson/status/1501306369319735300
Added in : wch/r-source@587244f

Currently, the IDE is throwing a "Unexpected token error"

Opening the issue just to be sure it is on your radar.

[ronblum]

Triage: Would this need to be backported?

[jmcphers]

Yes, we'd want to backport it to supported releases.

[kevinushey]

I'll take a look. (We'll probably support _ in the tokenizer in all places for backport, and then consider a change in SW where the diagnostics engine warns if _ is used in an incorrect context.)

[mikebessuille]

we want to backport this (PT includes some support for R4.2) but don't need to urgently backport this into 2022.02.1

[ronblum]

Testing with the following examples (details to follow):

R Source

# Example of of native pipe placeholder orig. from pipeOp
mtcars |> subset(cyl == 4) |> lm(mpg ~ disp, data = _)

# Example from QA notes
mtcars |> summary(object = _)

# Making sure that putting the entire statement in a function doesn't matter
fc <- function(c){
  mtcars |> subset(cyl == 4) |> lm(mpg ~ disp, data = _)
}
fc(1)

# Also making sure that putting the statement in a function doesn't matter
fd <- function(d){
  mtcars |> summary(object = _)
}
fc(1)

# Using a user-defined function
fab <- function(a, b){
  print(b)
}
12 |> fab(1, b = _)

R Markdown

---
title: "Placeholder"
author: "New Pipe"
date: '2022-04-14'
output: html_document
---

```{r}
# Example of of native pipe placeholder orig. from pipeOp
mtcars |> subset(cyl == 4) |> lm(mpg ~ disp, data = _)

# Example from QA notes
mtcars |> summary(object = _)

# Making sure that putting the entire statement in a function doesn't matter
fc <- function(c){
  mtcars |> subset(cyl == 4) |> lm(mpg ~ disp, data = _)
}
fc(1)

# Also making sure that putting the statement in a function doesn't matter
fd <- function(d){
  mtcars |> summary(object = _)
}
fc(1)

# Using a user-defined function
fab <- function(a, b){
  print(b)
}
12 |> fab(1, b = _)
```

[ronblum]

Tested in:

• RStudio Desktop 2022.02.2+481 & 2022.6.0+296 on MacOS 12.3 with R 4.2.0
• RStudio Server 2022.6.0+296 on Ubuntu 20.04 with R 4.1.2

[Ghost Orchid patch 3 TBD]

Results:

1. The new native pipe operator's placeholder (_) is no longer identified as an error
   (cf. to 2022.02.1+461 as a baseline).
2. There's no difference between the R script and R Markdown.
3. There's no difference between R versions—we treat the placeholder as not-an-error regardless, even though it's only supported by R 4.2.0.
4. However, while this example is treated as fine:
   mtcars |> subset(cyl == 4) |> lm(mpg ~ disp, data = _)
   this example has a "no symbol named '_' in scope" warning associated with it:
   mtcars |> summary(object = _)

[ronblum]

I think we don't want to show this warning, either, so putting this back into "in progress." But I can open a separate issue for this instead, since at least we're no longer flagging this as an error.

[ronblum]

Verified fixed in RStudio Desktop 2021.09.3-395, 2022.02.2-485, and 2022.06.0-313.