[Rd] Depends: R (>= 4.1) for packages that use |> and \(...)

[Ivan Krylov]

Many thanks to Henrik for remembering the report in Bugzilla and to
Kurt for implementing the change and finding out the true number of
affected packages.

On Wed, 22 Jan 2025 15:34:41 -0500
Ian Farm <ian.farm using maine.edu> wrote:

> Would packages using the underscore placeholder with the native pipe
> need to also depend on R >= 4.2.0?

That's a good find! For the R >= 4.2 syntax, we only need to check for
getParseData(...)$token %in% 'PLACEHOLDER'. The R >= 4.3 syntax feature
is harder to test for:

>> As an experimental feature the placeholder _ can now also be used in
>> the rhs of a forward pipe |> expression as the first argument in an
>> extraction call, such as _$coef. More generally, it can be used as
>> the head of a chain of extractions, such as _$coef[[2]]. 

I think it might be possible to parse(text = paste('PLACEHOLDER |>',
grandparent_expression)) and then look at the top-level function in the
call, but that feels quite fragile:

x <- utils::getParseData(parse(f, keep.source = TRUE))
i <- x$token %in% "PLACEHOLDER"
pi <- x[i, "parent"]
ppi <- x[x$id %in% pi, "parent"]
placeholder_expressions <- utils::getParseText(x, ppi)
extractor_used <- vapply(placeholder_expressions, function(src) {
 toplevel <- parse(text = paste("PLACEHOLDER |> ", src))[[1]][[1]]
 identical(toplevel, quote(`$`)) ||
  identical(toplevel, quote(`[`)) ||
  identical(toplevel, quote(`[[`))
}, FALSE)

Alternatively, we may find the first child of the grandparent of the
placeholder. If it's the placeholder expression, then the pipe must be
of the form ...|> _..., which is the R >= 4.3 syntax:

x <- utils::getParseData(parse(f, keep.source = TRUE))
i <- x$token %in% "PLACEHOLDER"
vapply(which(i), function(i) {
 pi <- x[i, "parent"]
 ppi <- x[x$id %in% pi, "parent"]
 cppi <- x[x$parent %in% ppi, "id"]
 min(cppi) == pi
}, FALSE)

-- 
Best regards,
Ivan