Safer latex_dependency insertion

[cderv]

rmarkdown/R/latex_dependencies.R

Lines 48 to 59 in ee69d59

	# return the LaTeX dependencies as a string suitable for inclusion
	# in the head of a document
	latex_dependencies_as_string <- function(dependencies) {
	lines <- sapply(dependencies, function(dep) {
	opts <- paste(dep$options, collapse = ",")
	if (opts != "") opts <- paste0("[", opts, "]")
	# \\usepackage[opt1,opt2]{pkgname}
	pkg <- paste0("\\usepackage", opts, "{", dep$name, "}")
	one_string(c(pkg, dep$extra_lines))
	})
	one_string(unique(lines))
	}

I wonder if it would be ok to use safer inclusion to avoid potential conflict if this is used in a document where the is already loaded package 🤔

Using \@ifpackageloaded{pkgname}{}{\usepackage[options]{name}}

If a package needs options to be set though, there is not really a good way to avoid option conflict, unless this is loaded before documentclass with \PassOptionsToPackage{options}{pkgname}

Anyhow, I feel latex_dependency is not that much used, and if it would be it need to be safer.

For thoughts...

[yihui]

Perhaps using \@ifpackageloaded{pkgname} only when opts == ''? That means, if users don't need any options, we can guarantee that the package will be loaded without conflicts. If they do, we just respect the options, which may or may not lead to conflicts.

[cderv]

Yes definitely - \@ifpackageloaded{pkgname} should be only used if opts == ''. I like that. thanks !