clojurescript silently ignores missing externs files possibly leading a developer to chase their tail.
Presently it can be very confusing using advanced compilation if you have made a mistake in the path name of one of your :externs files. This patch makes the compiler print a warning on stderr so you can quickly determine the cause of the broken advanced compilation output.
As a side effect, when doing a basic lein-cljsbuild a warning is always printed:
WARNING: js resource path closure-js/externs does not exist
This is because lein-cljsbuild quietly adds this extra path to your :externs listing without you knowing.
java version "1.7.0_65"
OpenJDK Runtime Environment (IcedTea 2.5.3) (7u71-2.5.3-0ubuntu0.14.04.1)
OpenJDK 64-Bit Server VM (build 24.65-b04, mixed mode)