Util::ScopedHashOverride

lib/vagrant/util/scoped_hash_override.rb

@@ -0,0 +1,40 @@
+module Vagrant
+  module Util
+    # This allows for hash options to be overridden by a scope key
+    # prefix. An example speaks best here. Imagine the following hash:
+    #
+    #     original = {
+    #       :id => "foo",
+    #       :mitchellh__id => "bar",
+    #       :mitchellh__other => "foo"
+    #     }
+    #
+    #     scoped = scoped_hash_override(original, "mitchellh")
+    #
+    #     scoped == {
+    #       :id => "bar",
+    #       :other => "foo"
+    #     }
+    #
+    module ScopedHashOverride
+      def scoped_hash_override(original, scope)
+        result = original.dup
+
+        original.each do |key, value|
+          parts = key.to_s.split("__", 2)
+
+          # If we don't have the proper parts, then bail
+          next if parts.length != 2
+
+          # If this is our scope, then override
+          if parts[0] == scope
+            result[parts[1].to_sym] = value
+            result.delete(key)
+          end
+        end
+
+        result
+      end
+    end
+  end
+end

test/unit/vagrant/util/scoped_hash_override_test.rb

@@ -0,0 +1,48 @@
+require File.expand_path("../../../base", __FILE__)
+
+require "vagrant/util/scoped_hash_override"
+
+describe Vagrant::Util::ScopedHashOverride do
+  let(:klass) do
+    Class.new do
+      extend Vagrant::Util::ScopedHashOverride
+    end
+  end
+
+  it "should not mess with non-overrides" do
+    original = {
+      :key => "value",
+      :another_value => "foo"
+    }
+
+    klass.scoped_hash_override(original, "foo").should == original
+  end
+
+  it "should override if the scope matches" do
+    original = {
+      :key => "value",
+      :scope__key => "replaced"
+    }
+
+    expected = {
+      :key => "replaced"
+    }
+
+    klass.scoped_hash_override(original, "scope").should == expected
+  end
+
+  it "should ignore non-matching scopes" do
+    original = {
+      :key => "value",
+      :scope__key => "replaced",
+      :another__key => "value"
+    }
+
+    expected = {
+      :key => "replaced",
+      :another__key => "value"
+    }
+
+    klass.scoped_hash_override(original, "scope").should == expected
+  end
+end