Warn users about unknown requested experimental features

bin/vagrant

@@ -172,6 +172,13 @@ begin
     logger.debug("Experimental flag is enabled")
     if Vagrant::Util::Experimental.global_enabled?
       ui.warn(I18n.t("vagrant.general.experimental.all"), bold: true, prefix: true, channel: :error)
+    else
+      ui.warn(I18n.t("vagrant.general.experimental.features", features: experimental.join(", ")), bold: true, prefix: true, channel: :error)
+
+      diff = Vagrant::Util::Experimental.features_valid?
+      if !diff.empty?
+        ui.error(I18n.t("vagrant.general.experimental.unknown_features", unknown: diff.join(", ")), bold: true, prefix: true, channel: :error)
+      end
     end
   end
 

lib/vagrant/util/experimental.rb

@@ -45,14 +45,19 @@ module Vagrant
           experimental = features_requested
           feature = feature.to_s
 
-          if experimental.size == 1 && experimental.first == "1"
-            return true
-          elsif VALID_FEATURES.include?(feature) &&
-                experimental.include?(feature)
-            return true
-          else
-            return false
+          return global_enabled? || (VALID_FEATURES.include?(feature) && experimental.include?(feature))
+        end
+
+        # Determines if there are any unrecognized requested features
+        #
+        # @return [Array]
+        def features_valid?
+          if !defined?(@_features_diff)
+            @_features_diff = []
+            features = features_requested
+            features.each { |f| @_features_diff << f if !VALID_FEATURES.include?(f) }
           end
+          @_features_diff
         end
 
         # Returns the features requested for the experimental flag

templates/locales/en.yml

@@ -405,6 +405,10 @@ en:
 
           Please use with caution, as some of the features may not be fully
           functional yet.
+        unknown_features: |-
+          Requested unknown feature flags will be ignored:
+
+          Unknown:   %{unknown}
       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

test/unit/vagrant/util/experimental_test.rb

@@ -98,6 +98,22 @@ describe Vagrant::Util::Experimental do
     end
   end
 
+  describe "#features_valid" do
+    before(:each) do
+      stub_const("Vagrant::Util::Experimental::VALID_FEATURES", ["cool_feature", "other_feature", "secret_feature"])
+    end
+
+    it "returns an empty array if no diffs found" do
+      allow(ENV).to receive(:[]).with("VAGRANT_EXPERIMENTAL").and_return("cool_feature,other_feature")
+      expect(subject.features_valid?).to eq([])
+    end
+
+    it "returns the invalid flag if found" do
+      allow(ENV).to receive(:[]).with("VAGRANT_EXPERIMENTAL").and_return("fake_feature")
+      expect(subject.features_valid?).to eq(["fake_feature"])
+    end
+  end
+
   describe "#features_requested" do
     it "returns an array of requested features" do
       allow(ENV).to receive(:[]).with("VAGRANT_EXPERIMENTAL").and_return("secret_feature,other_secret")