providers/docker: single port works [GH-3991]

CHANGELOG.md

@@ -38,6 +38,7 @@ BUG FIXES:
   - guests/windows: Reboot after hostname change. [GH-3987]
   - hosts/arch: NFS works with latest versions. [GH-4224]
   - hosts/windows: RDP command works without crash. [GH-3962]
+  - providers/docker: Port on its own will choose random host port. [GH-3991]
   - providers/virtualbox: Increase network device limit to 36. [GH-4206]
   - provisioners/chef: Chef client cleanup should work. [GH-4099]
   - provisioners/puppet: Manifest file can be a directory. [GH-4169]

plugins/providers/docker/action/create.rb

@@ -114,20 +114,32 @@ module VagrantPlugins
 
         def forwarded_ports(include_ssh=false)
           mappings = {}
+          random = []
+
           @machine.config.vm.networks.each do |type, options|
             next if type != :forwarded_port
 
             # Don't include SSH if we've explicitly asked not to
             next if options[:id] == "ssh" && !include_ssh
 
+            # If the guest port is 0, put it in the random group
+            if options[:guest] == 0
+              random << options[:host]
+              next
+            end
+
             mappings[options[:host]] = options
           end
 
-          mappings.values.map do |fp|
+          # Build the results
+          result = random.map(&:to_s)
+          result += mappings.values.map do |fp|
             protocol = ""
             protocol = "/udp" if fp[:protocol].to_s == "udp"
             "#{fp[:host]}:#{fp[:guest]}#{protocol}"
           end.compact
+
+          result
         end
       end
     end