Filter synced folders by allowed_synced_folder_types

lib/vagrant/action/builtin/mixin_synced_folders.rb

@@ -25,6 +25,13 @@ module Vagrant
           # Order the plugins by priority. Higher is tried before lower.
           ordered = ordered.sort { |a, b| b[0] <=> a[0] }
 
+          allowed_types = machine.config.vm.allowed_synced_folder_types
+          if allowed_types
+            ordered = ordered.select do |_, key, impl|
+              allowed_types.include? key
+            end
+          end
+
           # Find the proper implementation
           ordered.each do |_, key, impl|
             return key if impl.new.usable?(machine)

plugins/kernel_v2/config/vm.rb

@@ -14,6 +14,7 @@ module VagrantPlugins
     class VMConfig < Vagrant.plugin("2", :config)
       DEFAULT_VM_NAME = :default
 
+      attr_accessor :allowed_synced_folder_types
       attr_accessor :base_mac
       attr_accessor :boot_timeout
       attr_accessor :box
@@ -36,6 +37,7 @@ module VagrantPlugins
       attr_reader :provisioners
 
       def initialize
+        @allowed_synced_folder_types  = UNSET_VALUE
         @base_mac                     = UNSET_VALUE
         @boot_timeout                 = UNSET_VALUE
         @box                          = UNSET_VALUE
@@ -347,6 +349,7 @@ module VagrantPlugins
 
       def finalize!
         # Defaults
+        @allowed_synced_folder_types = nil if @allowed_synced_folder_types == UNSET_VALUE
         @base_mac = nil if @base_mac == UNSET_VALUE
         @boot_timeout = 300 if @boot_timeout == UNSET_VALUE
         @box = nil if @box == UNSET_VALUE

test/unit/vagrant/action/builtin/mixin_synced_folders_test.rb

@@ -28,14 +28,26 @@ describe Vagrant::Action::Builtin::MixinSyncedFolders do
     end
   end
 
-  let(:vm_config) { double("machine_vm_config") }
+  let(:vm_config) { double("machine_vm_config", :allowed_synced_folder_types => nil) }
 
   describe "default_synced_folder_type" do
     it "returns the usable implementation" do
       plugins = {
         "bad" => [impl(false, "bad"), 0],
-        "nope" => [impl(true, "nope"), 1],
-        "good" => [impl(true, "good"), 5],
+        "good" => [impl(true, "good"), 1],
+        "best" => [impl(true, "best"), 5],
+      }
+
+      result = subject.default_synced_folder_type(machine, plugins)
+      expect(result).to eq("best")
+    end
+
+    it "filters based on allowed_synced_folder_types" do
+      expect(vm_config).to receive(:allowed_synced_folder_types).and_return(["bad", "good"])
+      plugins = {
+        "bad" => [impl(false, "bad"), 0],
+        "good" => [impl(true, "good"), 1],
+        "best" => [impl(true, "best"), 5],
       }
 
       result = subject.default_synced_folder_type(machine, plugins)