Capture missing key calls in V1 configs and record them as warnings

lib/vagrant/config/v1/root.rb

@@ -1,3 +1,6 @@
+require "ostruct"
+require "set"
+
 module Vagrant
   module Config
     module V1
@@ -9,8 +12,9 @@ module Vagrant
         #
         # @param [Hash] config_map Map of key to config class.
         def initialize(config_map, keys=nil)
-          @keys       = keys || {}
-          @config_map = config_map
+          @keys              = keys || {}
+          @config_map        = config_map
+          @missing_key_calls = Set.new
         end
 
         # We use method_missing as a way to get the configuration that is
@@ -25,8 +29,9 @@ module Vagrant
             @keys[name] = config_klass.new
             return @keys[name]
           else
-            # Super it up to probably raise a NoMethodError
-            super
+            # Record access to a missing key as an error
+            @missing_key_calls.add(name.to_s)
+            return OpenStruct.new
           end
         end
 
@@ -45,8 +50,9 @@ module Vagrant
         # clashes with potential configuration keys.
         def __internal_state
           {
-            "config_map" => @config_map,
-            "keys"       => @keys
+            "config_map"        => @config_map,
+            "keys"              => @keys,
+            "missing_key_calls" => @missing_key_calls
           }
         end
       end

lib/vagrant/config/v2/loader.rb

@@ -119,6 +119,10 @@ module Vagrant
             end
           end
 
+          old.__internal_state["missing_key_calls"].to_a.sort.each do |key|
+            warnings << I18n.t("vagrant.config.loader.bad_v1_key", :key => key)
+          end
+
           [root, warnings, errors]
         end
 

templates/locales/en.yml

@@ -397,6 +397,10 @@ en:
         run_list_empty: "Run list must not be empty."
         server_url_empty: "Chef server URL must be populated."
         validation_key_path: "Validation key path must be valid path to your chef server validation key."
+      loader:
+        bad_v1_key: |-
+          Unknown configuration section '%{key}'. If this section was part of
+          a Vagrant 1.0.x plugin, note that 1.0.x plugins are incompatible with 1.1+.
       root:
         bad_key: |-
           Unknown configuration section '%{key}'.