Add shim for system.file to work with devtools-loaded packages

[wch]

This addresses rstudio/shiny#2468. Now when devtools::test(, "bootstrap") is called for shiny, it no longer has errors.

[cpsievert]

Hmm, I don't see any errors when I run devtools::test(, "bootstrap") on rstudio/shiny@d35c5c8

(Update: It wasn't failing because of the workaround I have in my .Rprofile)

[cpsievert]

Just cause I'm curious, how does find.package() know to return the source path and not the installed path?

htmltools/R/shim.R

Line 20 in aad84f5

pkg_path <- find.package(package)

[cpsievert]

Maybe we should use pkgload::dev_meta() if pkgload is installed (to help protect against internal changes to dev_meta())

htmltools/R/shim.R

Line 4 in aad84f5

if (is.null(ns) || is.null(ns$.__DEVTOOLS__)) {

[wch]

The reason to not use pkgload::dev_meta() is because then htmltools will take a dependency on pkgload.

[wch]

Just cause I'm curious, how does find.package() know to return the source path and not the installed path?

R doesn't have a concept of source path vs. installed path; it just has a concept of installed path. So when devtools loads a package, it tells R that the installed path is the source path.

[cpsievert]

I was thinking we'd have pkgload in suggests (or not at all with a getFromNamespace() workaround), but I don't feel that strongly about it, so you have my 👍 either way

if (system.file(package = "pkgload") != "") {
  return(!is.null(pkgload::dev_meta(package)))
} else if (is.null(ns) || is.null(ns$.__DEVTOOLS__)) {
  return(FALSE)
}

[wch]

Thanks - I'd still rather not take any sort of dependency on pkgload. The worst that can happen if pkgload decides to change the .__DEVTOOLS__ thing to something else is that this will no longer work, and the user will be in the same situation that exists currently.

Also, if we do use pkgload::dev_meta, then, if the user has pkgload installed, that line will cause the pkgload package to load (along with its dependencies) just to make this check, and that's way more heavyweight than is necessary here.