Fix up local gem plugin installation when not published remotely

lib/vagrant/bundler.rb

@@ -140,19 +140,14 @@ module Vagrant
     # @param [String] path Path to a local gem file.
     # @return [Gem::Specification]
     def install_local(path)
-      installer = Gem::Installer.at(path,
-        ignore_dependencies: true,
-        install_dir: plugin_gem_path.to_s
-      )
-      installer.install
-      new_spec = installer.spec
+      plugin_source = Gem::Source::SpecificFile.new(path)
       plugin_info = {
-        new_spec.name => {
-          'gem_version' => new_spec.version.to_s
+        plugin_source.spec.name => {
+          'local_source' => plugin_source
         }
       }
       internal_install(plugin_info, {})
-      new_spec
+      plugin_source.spec
     end
 
     # Update updates the given plugins, or every plugin if none is given.
@@ -231,6 +226,8 @@ module Vagrant
 
       update = {} unless update.is_a?(Hash)
 
+      installer_set = Gem::Resolver::InstallerSet.new(:both)
+
       # Generate all required plugin deps
       plugin_deps = plugins.map do |name, info|
         if update == true || (update[:gems].respond_to?(:include?) && update[:gems].include?(name))
@@ -238,6 +235,9 @@ module Vagrant
         else
           gem_version = info['gem_version'].to_s.empty? ? '> 0' : info['gem_version']
         end
+        if plugin_source = info.delete("local_source")
+          installer_set.add_local(plugin_source.spec.name, plugin_source.spec, plugin_source)
+        end
         Gem::Dependency.new(name, gem_version)
       end
 
@@ -254,7 +254,7 @@ module Vagrant
       request_set.import(existing_deps)
 
       # Generate the required solution set for new plugins
-      solution = request_set.resolve(Gem::Resolver::InstallerSet.new(:both))
+      solution = request_set.resolve(installer_set)
 
       # If any items in the solution set are local but not activated, turn them on
       solution.each do |activation_request|

lib/vagrant/plugin/manager.rb

@@ -47,7 +47,6 @@ module Vagrant
           local_spec = Vagrant::Bundler.instance.install_local(name)
           name       = local_spec.name
           opts[:version] = local_spec.version.to_s
-          local      = true
         end
 
         plugins = installed_plugins
@@ -57,21 +56,24 @@ module Vagrant
           "sources"     => opts[:sources],
         }
 
-        result = nil
-        install_lambda = lambda do
-          Vagrant::Bundler.instance.install(plugins, local).each do |spec|
-            next if spec.name != name
-            next if result && result.version >= spec.version
-            result = spec
+        if local_spec.nil?
+          result = nil
+          install_lambda = lambda do
+            Vagrant::Bundler.instance.install(plugins, local).each do |spec|
+              next if spec.name != name
+              next if result && result.version >= spec.version
+              result = spec
+            end
           end
-        end
 
-        if opts[:verbose]
-          Vagrant::Bundler.instance.verbose(&install_lambda)
+          if opts[:verbose]
+            Vagrant::Bundler.instance.verbose(&install_lambda)
+          else
+            install_lambda.call
+          end
         else
-          install_lambda.call
+          result = local_spec
         end
-
         # Add the plugin to the state file
         @user_file.add_plugin(
           result.name,