Saving to svg without svglite installed throws unhelpful error

[eliocamp]

Trying to save a plot to svg without svsglite installed (which is possible because svglite is a Suggest) throws this error:

> ggsave("poster.svg")
Saving 7 x 7 in imageError in loadNamespace(x) : there is no package called ‘svglite’

The error is not very helpful as it doesn't tell the user what the issue is and how to resolve it.

The problem is that plot_dev doesn't check if svglite is installed here:

ggplot2/R/save.R

Line 280 in b174986

svg = function(filename, ...) svglite::svglite(file = filename, ...),

so R errors out when trying to evaluate the dev function; probably here:

ggplot2/R/save.R

Line 109 in b174986

dev(filename = filename, width = dim[1], height = dim[2], bg = bg, ...)

Maybe a better alternative would be to do something like this:

svg =  function(filename, ...) { 
   check_installed("svglite", reason = "to save as SVG.")
   svglite::svglite(file = filename, ...)
} 

[teunbrand]

This sounds reasonable to me. Do you happen to have any interest in preparing a PR for this?

[eliocamp]

Done!