Fix handling of IO#timeout.

lib/async/scheduler.rb

@@ -173,6 +173,10 @@ def io_wait(io, events, timeout = nil)
 				timer = @timers.after(timeout) do
 					fiber.transfer
 				end
+			elsif timeout = io.timeout
+				timer = @timers.after(timeout) do
+					fiber.raise(::IO::TimeoutError, "Timeout while waiting for IO to become ready!")
+				end
 			end
 
 			return @selector.io_wait(fiber, io, events)
@@ -182,12 +186,32 @@ def io_wait(io, events, timeout = nil)
 
 		if ::IO::Event::Support.buffer?
 			def io_read(io, buffer, length, offset = 0)
-				@selector.io_read(Fiber.current, io, buffer, length, offset)
+				fiber = Fiber.current
+
+				if timeout = io.timeout
+					timer = @timers.after(timeout) do
+						fiber.raise(::IO::TimeoutError, "execution expired")
+					end
+				end
+
+				@selector.io_read(fiber, io, buffer, length, offset)
+			ensure
+				timer&.cancel
 			end
 
 			if RUBY_ENGINE != "ruby" || RUBY_VERSION >= "3.3.0"
 				def io_write(io, buffer, length, offset = 0)
-					@selector.io_write(Fiber.current, io, buffer, length, offset)
+					fiber = Fiber.current
+
+					if timeout = io.timeout
+						timer = @timers.after(timeout) do
+							fiber.raise(::IO::TimeoutError, "execution expired")
+						end
+					end
+
+					@selector.io_write(fiber, io, buffer, length, offset)
+				ensure
+					timer&.cancel
 				end
 			end
 		end

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(Async::TimeoutError)
+			end.to raise_exception(IO::TimeoutError)
 		end
 
 		it "can wait for readability in sequential tasks" do

test/io.rb

@@ -30,5 +30,31 @@
 			input.close
 			output.close
 		end
+
+		it "can read with timeout" do
+			input, output = IO.pipe
+			input.timeout = 0.001
+
+			expect do
+				line = input.gets
+			end.to raise_exception(::IO::TimeoutError)
+		end
+
+		it "can wait readable with default timeout" do
+			input, output = IO.pipe
+			input.timeout = 0.001
+
+			expect do
+				# This behaviour is not consistent with non-fiber scheduler IO.
+				# However, this is the best we can do without fixing CRuby.
+				input.wait_readable
+			end.to raise_exception(::IO::TimeoutError)
+		end
+
+		it "can wait readable with 0 timeout" do
+			input, output = IO.pipe
+
+			expect(input.wait_readable(0)).to be_nil
+		end
 	end
 end