issue warning on empty return set

[SymbolixAU]

No description provided.

[jonocarroll]

For a ZERO_RESULTS return, try

> google_directions(origin = "Adelaide, South Australia", destination = "New York, New York", key="")
$available_travel_modes
[1] "DRIVING"   "BICYCLING" "WALKING"  

$geocoded_waypoints
  geocoder_status                    place_id                                types
1              OK ChIJP7Mmxcc1t2oRQMaOYlQ2AwQ colloquial_area, locality, political
2              OK ChIJOwg_06VPwokRYv534QaPC8g                  locality, political

$routes
list()

$status
[1] "ZERO_RESULTS"

It's not necessarily your package's duty to do this checking, but it could. It would be good to document the returned list (when simplify=TRUE) and mention that there's a $status that is checked against (and potential values, likely listed in the API docs). It's particularly friendly to do so given that there's potential for an empty list() to be returned (the fun of lapply in jsonlite::simplify).

Handling of this case (and a successful one) should also appear in your automated package testing.

[SymbolixAU]

The problem with testing actual API calls is I would have to expose my API key (unless you know of another way?)

[jonocarroll]

I usually save the key in a hidden file on my local drive outside of the git scope (add to .gitignore just in case) then read it in to the field.

 APIkey <- c(read.dcf("~/.googleAPI", fields = c("GOOGLE_API_KEY")))

 google_directions(origin      = ltrip[[1]],
                   destination = ltrip[[length(ltrip)]],
                   mode        = "bicycling",
                   waypoints   = ltrip,
                   key         = APIkey)

I can adapt a setup_google() function I've already got somewhere if you like. It can be run at the start of API calling functions and will ensure that the session is authenticated before continuing, otherwise prompt for such.

I've made the mistake of committing a key before; don't do that.

You can do the function testing locally with this option and not epose your key. Refer to the Skipping a test section of http://r-pkgs.had.co.nz/tests.html to see how to not require this when testing externally. Also, skip_on_cran().