Factor out needs_packages()

[salim-b]

I just submitted #101 and now I'm wondering: Are there any plans on factoring out the needs_packages() function into a separate package? Or maybe introduce something similar in pak?

Currently, the function looks like this:

pkgsearch/R/utils.R

Lines 100 to 127 in 9c0102e

	needs_packages <- function(pkgs) {
	has <- map_lgl(pkgs, function(pkg) {
	requireNamespace(pkg, quietly = TRUE)
	})
	if (!all(has)) {
	not_installed_pkgs <- pkgs[!has]
	if (length(not_installed_pkgs) == 1) {
	throw(new_error(
	"The ",
	sQuote(not_installed_pkgs),
	" package is needed for this addin.",
	call. = FALSE
	))
	} else {
	throw(new_error(
	"The ",
	paste(sQuote(not_installed_pkgs), collapse = ", "),
	" packages are needed for this addin.",
	call. = FALSE
	))
	}
	}
	}

This implementation of course is not very sophisticated and it could be improved (i.a. provide an auto-generated code snippet to install the missing packages in the error message).

But it still provides a frequently used check: Test if package xyz, which is only suggested but not imported, is installed and if not, throw an informative error. I would really like to have a "standardized" way to do this!

[gaborcsardi]

Hi, yeah, I would not export this from pkgsearch.

It seems like you want to use this programmatically. I think introducing a new dependency for these 10 lines of mostly trivial code is probably not worth it, so I would say just copy this function into your package(s).

FWIW, there is also rlang::is_installed()

[salim-b]

yeah, I would not export this from pkgsearch.

Sure, I didn't really mean to export it in the current form, sorry for being a bit unclear. I was rather asking if there are any plans on your side (the people around tidyverse, r-lib, r-hub, RStudio etc.) on introducing such a function in a new (or existing, e.g. pak) package in the near future. 🙂

After all, it's an action that's frequently used in a lot of packages and it would be cool to have a best practice implementation in one place (kinda like rlang::arg_match() for argument matching).

But I guess your answer means there are no such plans, right?

FWIW, there is also rlang::is_installed()

Thanks for the hint! I just created r-lib/rlang#991 to make it vectorized... I hope you're not about to rip it right out of the air. 😅