Add presence helpers

lib/vagrant/util/presence.rb

@@ -0,0 +1,41 @@
+module Vagrant
+  module Util
+    module Presence
+      extend self
+
+      # Determines if the given object is "present". A String is considered
+      # present if the stripped contents are not empty. An Array/Hash is
+      # considered present if they have a length of more than 1. "true" is
+      # always present and `false` and `nil` are always not present. Any other
+      # object is considered to be present.
+      #
+      # @return [true, false]
+      def present?(obj)
+        case obj
+        when String
+          !obj.strip.empty?
+        when Array, Hash
+          !obj.empty?
+        when TrueClass, FalseClass
+          obj
+        when NilClass
+          false
+        when Object
+          true
+        end
+      end
+
+      # Returns the presence of the object. If the object is {present?}, it is
+      # returned. Otherwise `false` is returned.
+      #
+      # @return [Object, false]
+      def presence(obj)
+        if present?(obj)
+          obj
+        else
+          false
+        end
+      end
+    end
+  end
+end

test/unit/vagrant/util/presence_test.rb

@@ -0,0 +1,46 @@
+require File.expand_path("../../../base", __FILE__)
+
+require "vagrant/util/presence"
+
+describe Vagrant::Util::Presence do
+  subject { described_class }
+
+  describe "#presence" do
+    it "returns false for nil" do
+      expect(subject.presence(nil)).to be(false)
+    end
+
+    it "returns false for false" do
+      expect(subject.presence(false)).to be(false)
+    end
+
+    it "returns false for an empty string" do
+      expect(subject.presence("")).to be(false)
+    end
+
+    it "returns false for a string with null bytes" do
+      expect(subject.presence("\u0000")).to be(false)
+    end
+
+    it "returns false for an empty array" do
+      expect(subject.presence([])).to be(false)
+    end
+
+    it "returns false for an empty hash" do
+      expect(subject.presence({})).to be(false)
+    end
+
+    it "returns true for true" do
+      expect(subject.presence(true)).to be(true)
+    end
+
+    it "returns the object for an object" do
+      obj = Object.new
+      expect(subject.presence(obj)).to be(obj)
+    end
+
+    it "returns the class for a class" do
+      expect(subject.presence(String)).to be(String)
+    end
+  end
+end