On 25/01/2024 11:18 a.m., Henrik Bengtsson wrote:
On Thu, Jan 25, 2024 at 7:48 AM Duncan Murdoch <murdoch.dun...@gmail.com> wrote:

On 25/01/2024 10:27 a.m., Josiah Parry wrote:
Hey all,

I've encountered use of the native pipe operator in the examples for
'httr2' e.g.

request("http://example.com";) |> req_dry_run()

Since r-oldrel (according to rversions::r_oldrel()) is now 4.2.3, can the
native pipe be used in example code?

I do notice that the package httr2 requires R >= 3.6.0 which implies that
the code itself does not use the native pipe, but the examples do.

I think that the package should state it requires R (>= 4.1.0), since
that code won't work in earlier versions.

I believe it's a syntax error before 4.1.0, but don't have a copy handy
to test.

Yes, support for the |> syntax was introduced in R 4.1.0;

$ Rscript --vanilla -e "getRversion()" -e "1:10 |> sum()"
[1] ‘4.0.5’
Error: unexpected '>' in "1:10 |>"
Execution halted

$ Rscript --vanilla -e "getRversion()" -e "1:10 |> sum()"
[1] ‘4.1.0’
[1] 55

That means the package won't pass R CMD check in those old
versions.  If it wasn't a syntax error, just a case of using a new
feature, then I think it would be fine to put in a run-time test of the
R version to skip code that won't run properly.

There's also the distinction of package code versus code in
documentation. If it's only example code in help pages that use the
native pipe, but the code in R/*.R does not, then the package will
still install and work with R (< 4.1.0).  The only thing that won't
work is when the user tries to run the code in the documented
examples.  I'd argue that it's okay to specify, say, R (>= 3.6.0) in
such an example.  It allows users with older versions to still use the
package, while already now migrating the documentation to use newer

Is there a way to do that so that R will pay attention, or do you mean just saying it in a comment?

I think you're right that syntax errors in help page examples will be installable, but I don't think there's a way to make them pass "R CMD check" other than wrapping them in \dontrun{}, and I don't know a way to do that conditional on the R version.

I would say that a package that doesn't pass "R CMD check" without errors shouldn't be trusted.

Duncan Murdoch

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