Is there a general solution for parsing server error messages that aren't returned in the header in httr so that we can print error message for users in a package?

parse_error_messages.md

This is a call to the GBIF API. There is an intential error in the call that gives an error message from the server

com.spatial4j.core.exception.InvalidShapeException: Invalid latitude: latitudes are range -90 to 90: provided lat: [-125.0]

In R with httr:

library(httr)
call <- "http://api.gbif.org/v0.9/occurrence/search?geometry=POLYGON((38.4 -125, 40.9 -125, 40.9 -121.8, 38.4 -121.8, 38.4 -125))"
a <- GET(call)

None of the metadata from the call, as far as I know, gives the error message.

You can parse the message out

library(XML)
doc = htmlParse(content(a, as="text"))
xpathSApply(doc, "//h1", xmlValue)

[1] "HTTP Status 500 - com.spatial4j.core.exception.InvalidShapeException: Invalid latitude: latitudes are range -90 to 90: provided lat: [-125.0]"

But I wonder if there is a general solution available in httr that works beyond just this example.

Perhaps the server error above should be in the header?

Okay, thanks Hadley