From bc0643613a30a3848bbccc303d001783bb689877 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Sun, 6 May 2012 14:01:10 -0700
Subject: [PATCH] Vagrant.require_plugin [GH-916]

---
 CHANGELOG.md              |  3 ++-
 lib/vagrant.rb            | 16 ++++++++++++++++
 lib/vagrant/errors.rb     |  5 +++++
 templates/locales/en.yml  |  3 +++
 test/unit/vagrant_test.rb | 13 +++++++++++++
 5 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3fb10b693..4289948e2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,7 +7,8 @@
     not be _functional_ in future versions of Vagrant).
   - Plugins no longer "autoload" by simply gem installing them. This increases
     Vagrant's initial startup time considerably. To replace this, you must now
-    explicitly require plugins in the `~/.vagrantrc` file.
+    explicitly require plugins in the `~/.vagrantrc` file, using
+    `Vagrant.require_plugin`.
   - Improve the SSH "ready?" check. [GH-841]
   - Human friendly error if connection times out for HTTP downloads. [GH-849]
   - Detect when the VirtualBox installation is incomplete and error. [GH-846]
diff --git a/lib/vagrant.rb b/lib/vagrant.rb
index 1783dc27f..7adf8402f 100644
--- a/lib/vagrant.rb
+++ b/lib/vagrant.rb
@@ -107,6 +107,22 @@ module Vagrant
     # Raise an error that the plugin version is invalid
     raise ArgumentError, "Invalid plugin version API: #{version}"
   end
+
+  # This should be used instead of Ruby's built-in `require` in order to
+  # load a Vagrant plugin. This will load the given plugin by first doing
+  # a normal `require`, giving a nice error message if things go wrong,
+  # and second by verifying that a Vagrant plugin was actually defined in
+  # the process.
+  #
+  # @param [String] name Name of the plugin to load.
+  def self.require_plugin(name)
+    # Attempt the normal require
+    begin
+      require name
+    rescue LoadError
+      raise Errors::PluginLoadError, :plugin => name
+    end
+  end
 end
 
 # # Default I18n to load the en locale
diff --git a/lib/vagrant/errors.rb b/lib/vagrant/errors.rb
index 6f17fbfab..9a192386a 100644
--- a/lib/vagrant/errors.rb
+++ b/lib/vagrant/errors.rb
@@ -298,6 +298,11 @@ module Vagrant
       error_key(:dotfile_error, "vagrant.actions.vm.persist")
     end
 
+    class PluginLoadError < VagrantError
+      status_code(81)
+      error_key(:plugin_load_error)
+    end
+
     class SCPUnavailable < VagrantError
       status_code(56)
       error_key(:scp_unavailable)
diff --git a/templates/locales/en.yml b/templates/locales/en.yml
index 1d70599d0..deac589cb 100644
--- a/templates/locales/en.yml
+++ b/templates/locales/en.yml
@@ -83,6 +83,9 @@ en:
       no_env: |-
         A Vagrant environment is required to run this command. Run `vagrant init`
         to set one up.
+      plugin_load_error: |-
+        The plugin "%{plugin}" could not be found. Please make sure that it is
+        properly installed via `vagrant gem`.
       port_collision_resume: |-
         This VM cannot be resumed, because the forwarded ports would collide with
         another running virtual machine. Normally, Vagrant will attempt to fix this
diff --git a/test/unit/vagrant_test.rb b/test/unit/vagrant_test.rb
index a97ad657a..5dd502aa8 100644
--- a/test/unit/vagrant_test.rb
+++ b/test/unit/vagrant_test.rb
@@ -15,4 +15,17 @@ describe Vagrant do
         to raise_error(ArgumentError)
     end
   end
+
+  describe "requiring plugins" do
+    it "should require the plugin given" do
+      # For now, just require a stdlib
+      expect { described_class.require_plugin "set" }.
+        to_not raise_error
+    end
+
+    it "should raise an error if the file doesn't exist" do
+      expect { described_class.require_plugin("i_dont_exist") }.
+        to raise_error(Vagrant::Errors::PluginLoadError)
+    end
+  end
 end