In jennybc/reprex: Prepare Reproducible Example Code via the Clipboard

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  error = TRUE
)

Figuring out how to write RTF to the Windows clipboard made me think more about the functions system(), system2(), and (Windows only) shell().

Here's the highlight call used in reprex_rtf(), which converts such a .R file into RTF:

```{sh eval = FALSE} highlight -i foo_reprex.R --out-format rtf --no-trailing-nl --encoding=UTF-8 --style darkbone --font 'Courier Regular' --font-size 50 -o gamma_reprex.rtf

There are many ways to invoke this from R:

* `system()`: Docs say "not recommended for new code".
* `system2()`: Officially, the "right" thing to use, at least on *nix.
* `shell()`: Exists only on Windows. Explicitly runs `cmd` under a shell, which
  is not the case for `system()` or `system2()` on Windows.
* `processx::run()`

`system()` and `system2()` only differ with respect to how the ultimately-run command is constructed.
`system2()` is recommended for new code and takes care of some fiddly details, e.g. quoting.
However, due to quoting nightmares, there are calls that can only be formed by `system()` and some that can't be formed at all (which is one of the reasons processx exists).
The main thing to know is that on Windows `command` is executed directly, not within a shell, such as `cmd.exe` or `powershell.exe`.

This is easiest to see in an example.
`dir` is a command built into `cmd.exe`.
It will work inside `shell()` but not within `system()` or `system2()`.

```r
shell("dir", intern = TRUE)
print(system("dir"))
print(system2("dir"))

How did this come up? Depending on how you have installed highlight, the system() and shell() calls below might produce different results. Specifically, the system() call is reported to fail here if highlight was installed via scoop, which uses a shim-based method of putting things it installs on the PATH. This may additionally have something to do with Windows short paths (?).

system("highlight --version")
shell("highlight --version")
Sys.which("highlight")

In any case, my current hypothesis is that I should invoke highlight via shell() on Windows, to be more resilient to the different ways users may have installed highlight.

Let's prove I can invoke highlight in several ways by implementing reprex_rtf() "by hand". First, we render a reprex to the "r" venue and explicitly write a local output file.

library(reprex)

reprex_r(sample(LETTERS, 5), outfile = here::here("internal/gamma"))

The output of this gamma_reprex_rendered.R is the input for the next step, which is to form RTF.

More objects and helpers we'll use:

r_file <- here::here("internal/gamma_reprex_rendered.R")
rtf_file <- here::here("internal/gamma_reprex_rendered.rtf")

system()

(cmd <- glue::glue("
   highlight -i {r_file} --out-format=rtf --no-trailing-nl --encoding=UTF-8 \\
   -o {rtf_file}"))

system(cmd)

readLines(rtf_file)

system2()

unlink(rtf_file)

(args <- c(
  glue::glue("-i {r_file}"),
  "--out-format=rtf", "--no-trailing-nl", "--encoding=UTF-8",
  glue::glue("-o {rtf_file}")
))

print(system2("highlight", args))

readLines(rtf_file)

shell()

unlink(rtf_file)

(cmd <- glue::glue("
   highlight -i {r_file} --out-format=rtf --no-trailing-nl --encoding=UTF-8 \\
   -o {rtf_file}"))

print(shell(cmd))

readLines(rtf_file)

unlink(rtf_file)

print(shell(cmd, shell = "cmd"))

readLines(rtf_file)

unlink(rtf_file)

print(shell(cmd, shell = "powershell"))

readLines(rtf_file)

Clean up

unlink(list.files(here::here("internal"), pattern = "gamma_reprex", full.names = TRUE))

jennybc/reprex documentation built on Jan. 12, 2024, 9:33 p.m.