Support older rubies.

lib/async/scheduler.rb

@@ -165,15 +165,28 @@ def address_resolve(hostname)
 			::Resolv.getaddresses(hostname)
 		end
 
+
+		if IO.method_defined?(:timeout)
+			private def get_timeout(io)
+				io.timeout
+			end
+		else
+			private def get_timeout(io)
+				nil
+			end
+		end
+
 		# @asynchronous May be non-blocking..
 		def io_wait(io, events, timeout = nil)
 			fiber = Fiber.current
 
 			if timeout
+				# If an explicit timeout is specified, we expect that the user will handle it themselves:
 				timer = @timers.after(timeout) do
 					fiber.transfer
 				end
-			elsif timeout = io.timeout
+			elsif timeout = get_timeout(io)
+				# Otherwise, if we default to the io's timeout, we raise an exception:
 				timer = @timers.after(timeout) do
 					fiber.raise(::IO::TimeoutError, "Timeout while waiting for IO to become ready!")
 				end
@@ -183,12 +196,12 @@ def io_wait(io, events, timeout = nil)
 		ensure
 			timer&.cancel
 		end
-
+		
 		if ::IO::Event::Support.buffer?
 			def io_read(io, buffer, length, offset = 0)
 				fiber = Fiber.current
 
-				if timeout = io.timeout
+				if timeout = get_timeout(io)
 					timer = @timers.after(timeout) do
 						fiber.raise(::IO::TimeoutError, "execution expired")
 					end
@@ -203,7 +216,7 @@ def io_read(io, buffer, length, offset = 0)
 				def io_write(io, buffer, length, offset = 0)
 					fiber = Fiber.current
 
-					if timeout = io.timeout
+					if timeout = get_timeout(io)
 						timer = @timers.after(timeout) do
 							fiber.raise(::IO::TimeoutError, "execution expired")
 						end

lib/async/wrapper.rb

@@ -32,12 +32,12 @@ def dup
 
 		# Wait for the io to become readable.
 		def wait_readable(timeout = @timeout)
-			@io.to_io.wait_readable(timeout) or raise ::IO::TimeoutError
+			@io.to_io.wait_readable(timeout) or raise TimeoutError
 		end
 
 		# Wait for the io to become writable.
 		def wait_priority(timeout = @timeout)
-			@io.to_io.wait_priority(timeout) or raise ::IO::TimeoutError
+			@io.to_io.wait_priority(timeout) or raise TimeoutError
 		end
 
 		# Wait for the io to become writable.

test/async/wrapper.rb

@@ -33,7 +33,7 @@ def after
 		it "can timeout if no event occurs" do
 			expect do
 				output.wait_readable(0.001)
-			end.to raise_exception(IO::TimeoutError)
+			end.to raise_exception(Async::TimeoutError)
 		end
 
 		it "can wait for readability in sequential tasks" do

test/io.rb

@@ -32,6 +32,8 @@
 		end
 
 		it "can read with timeout" do
+			skip_unless_constant_defined(:TimeoutError, IO)
+
 			input, output = IO.pipe
 			input.timeout = 0.001
 
@@ -41,6 +43,8 @@
 		end
 
 		it "can wait readable with default timeout" do
+			skip_unless_constant_defined(:TimeoutError, IO)
+
 			input, output = IO.pipe
 			input.timeout = 0.001
 
@@ -51,7 +55,7 @@
 			end.to raise_exception(::IO::TimeoutError)
 		end
 
-		it "can wait readable with 0 timeout" do
+		it "can wait readable with explicit timeout" do
 			input, output = IO.pipe
 
 			expect(input.wait_readable(0)).to be_nil