Better plugin dev experience through warnings

CHANGELOG.md

@@ -6,6 +6,8 @@ IMPROVEMENTS:
   - Don't load `vagrant plugin` installed plugins when in a Bundler
     environment. This happens during plugin development. This will make
     Vagrant errors much quieter when developing plugins.
+  - Vagrant will detect Bundler environments, make assumptions that you're
+    developing plugins, and will quiet its error output a bit.
 
 BUG FIXES:
 

bin/vagrant

@@ -52,8 +52,23 @@ begin
   logger.debug("Creating Vagrant environment")
   env = Vagrant::Environment.new(opts)
 
-  # If we're not in the installer, warn.
-  env.ui.warn(I18n.t("vagrant.general.not_in_installer")) if !Vagrant.in_installer?
+  if !Vagrant.in_installer?
+    warned = false
+
+    # If we're in a bundler environment, we assume it is for plugin
+    # development and will let the user know that.
+    if defined?(Bundler)
+      require 'bundler/shared_helpers'
+      if Bundler::SharedHelpers.in_bundle?
+        env.ui.warn(I18n.t("vagrant.general.in_bundler"))
+        env.ui.warn("")
+        warned = true
+      end
+    end
+
+    # If we're not in the installer, warn.
+    env.ui.warn(I18n.t("vagrant.general.not_in_installer")) if !warned
+  end
 
   begin
     # Execute the CLI interface, and exit with the proper error code

templates/locales/en.yml

@@ -18,6 +18,11 @@ en:
 
         Old: %{old}
         New: %{new}
+      in_bundler: |-
+        You appear to be running Vagrant in a Bundler environment. Because
+        Vagrant should be run within installers (outside of Bundler), Vagrant
+        will assume that you're developing plugins and will change its behavior
+        in certain ways to better assist plugin development.
       not_in_installer: |-
         You appear to be running Vagrant outside of the official installers.
         Note that the installers are what ensure that Vagrant has all required