rack.rb in falcon-0.19.3

- old
+ new

@@ -16,10 +16,12 @@
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
+require 'rack'
+
 require_relative 'input'
 require_relative 'response'
 
 require 'async/logger'
 
@@ -32,9 +34,11 @@
 			CONTENT_TYPE = 'CONTENT_TYPE'.freeze
 			CONTENT_LENGTH = 'CONTENT_LENGTH'.freeze
 			
 			def initialize(app, logger = Async.logger)
 				@app = app
+				
+				raise ArgumentError, "App must be callable!" unless @app.respond_to?(:call)
 				
 				@logger = logger
 			end
 			
 			# Rack separates multiple headers with the same key, into a single field with multiple "lines".