Allow error handling

[gregmacfarlane]

I want to write exception handling in case the object I want to get from my bucket isn't there. I tried to surround this in tryCatch:

tryCatch({
  header <- head_object(object = "s3://mybucket/not_there.txt")
}, error = function(e){
  message("object not found")
  # code to get around it
})

Unfortunately, when the object is not available, head_object returns a message saying "Client error: (404) Not Found" instead of an error, so there is nothing to catch. I've gotten around this by saying doing

suppressMessages(  
  header <- aws.s3::head_object(object = "s3://mybucket/not_there.txt")
)
if(!header[1]){
  message("object not found")
  # code to get around it
}

because the first element in the returned object is a boolean indicating whether it was there or not, this works. But it feels unnatural. Is there a reason for this design decision? Is there a better way to handle exceptions?

By the way, I only came across this when I didn't find a function for check_exists(), which would seem to be a natural thing to have here.

[leeper]

Thanks for this. Will reply again when I've got this working better.

[leeper]

Give the new object_exists() function a try, which should return a logical. Added via: 927f38f from #234