Add extra_args cap for darwin rdp

This commit fixes GH-5523.

plugins/hosts/darwin/cap/rdp.rb

@@ -8,6 +8,15 @@ module VagrantPlugins
     module Cap
       class RDP
         def self.rdp_client(env, rdp_info)
+          config_path = self.generate_config_file(rdp_info)
+          Vagrant::Util::Subprocess.execute("open", config_path.to_s)
+        end
+
+        protected
+
+        # Generates an RDP connection file and returns the resulting path.
+        # @return [String]
+        def self.generate_config_file(rdp_info)
           opts   = {
             "drivestoredirect:s"       => "*",
             "full address:s"           => "#{rdp_info[:host]}:#{rdp_info[:port]}",
@@ -22,10 +31,15 @@ module VagrantPlugins
             opts.each do |k, v|
               f.puts("#{k}:#{v}")
             end
+
+            if rdp_info[:extra_args]
+              rdp_info[:extra_args].each do |arg|
+                f.puts("#{arg}")
+              end
+            end
           end
 
-          # Launch it
-          Vagrant::Util::Subprocess.execute("open", config_path.to_s)
+          return config_path
         end
       end
     end

test/unit/plugins/hosts/darwin/cap/rdp_test.rb

@@ -0,0 +1,36 @@
+require_relative "../../../../base"
+
+require_relative "../../../../../../plugins/hosts/darwin/cap/rdp"
+
+describe VagrantPlugins::HostDarwin::Cap::RDP do
+  let(:rdp_info) do
+    {
+      host: "host",
+      port: "port",
+      username: "username",
+    }
+  end
+
+  it "includes the default options" do
+    path = described_class.generate_config_file(rdp_info)
+    result = File.read(path)
+    expect(result).to match("drivestoredirect:s:*")
+    expect(result).to match("full address:s:host:port")
+    expect(result).to match("prompt for credentials:i:1")
+    expect(result).to match("username:s:username")
+  end
+
+  it "includes extra RDP arguments" do
+    rdp_info.merge!(extra_args: ["screen mode id:i:0"])
+    path = described_class.generate_config_file(rdp_info)
+    result = File.read(path)
+    expect(result).to match("screen mode id:i:0")
+  end
+
+  it "opens the RDP file" do
+    env = double(:env)
+    allow(described_class).to receive(:generate_config_file).and_return("/path")
+    expect(Vagrant::Util::Subprocess).to receive(:execute).with("open", "/path")
+    described_class.rdp_client(env, rdp_info)
+  end
+end

website/source/docs/cli/rdp.html.md

@@ -23,8 +23,21 @@ these through. For example:
 
 ```
 $ vagrant rdp -- /span
-...
 ```
 
 The above command on Windows will execute `mstsc.exe /span config.rdp`,
 allowing your RDP to span multiple desktops.
+
+
+On Darwin hosts, such as Mac OS X, the additional arguments are added to the
+generated RDP configuration file. Since these files can contain multiple options
+with different spacing, you _must_ quote multiple arguments. For example:
+
+```
+$ vagrant rdp -- "screen mode id:i:0" "other config:s:value"
+```
+
+Note that as of the publishing of this guide, the Microsoft RDP Client for Mac
+does _not_ perform validation on the configuration file. This means if you
+specify an invalid configuration option or make a typographical error, the
+client will silently ignore the error and continue!