Resolve AAAA before A in address_resolve.

Author: wtn

lib/async/scheduler.rb

@@ -295,7 +295,22 @@ def address_resolve(hostname)
 			# On some platforms, hostnames may contain a device-specific suffix (e.g. %en0). We need to strip this before resolving.
 			# See <https://github.com/socketry/async/issues/180> for more details.
 			hostname = hostname.split("%", 2).first
-			::Resolv.getaddresses(hostname)
+			
+			return [hostname] if ::Resolv::AddressRegex =~ hostname
+			
+			addresses = ::Resolv::Hosts.new.getaddresses(hostname)
+			
+			if addresses.empty?
+				dns = ::Resolv::DNS.new
+				[::Resolv::DNS::Resource::IN::AAAA, ::Resolv::DNS::Resource::IN::A].each do |type|
+					dns.each_resource(hostname, type) {|resource| addresses << resource.address.to_s}
+				end
+			else
+				ipv6, ipv4 = addresses.partition {|address| address.include?(":")}
+				addresses = ipv6 + ipv4
+			end
+			
+			addresses
 		end
 
 		# Wait for the specified IO to become ready for the specified events.

test/async/scheduler/address.rb

@@ -34,4 +34,18 @@
 			expect(address.ipv6?).to be == true
 		end
 	end
+
+	with "#address_resolve" do
+		it "preserves the platform's address selection ordering" do
+			hostname = "localhost"
+			
+			expected = Socket.getaddrinfo(hostname, nil, Socket::AF_UNSPEC, Socket::SOCK_STREAM)
+				.map {|info| info[3]}
+				.uniq
+				
+			actual = Fiber.scheduler.address_resolve(hostname)
+			
+			expect(actual).to be == expected
+		end
+	end
 end