Add PluginSupport module

lib/standard.rb

@@ -13,3 +13,4 @@ module Standard
 require "standard/formatter"
 
 require "standard/plugin"
+require "standard/plugin_support"

lib/standard/plugin_support.rb

@@ -0,0 +1 @@
+require "standard/plugin_support/merges_upstream_metadata"

lib/standard/plugin_support/merges_upstream_metadata.rb

@@ -0,0 +1,23 @@
+module Standard
+  module PluginSupport
+    class MergesUpstreamMetadata
+      def merge(plugin_yaml, upstream_yaml)
+        common_upstream_values = upstream_yaml.select { |key| plugin_yaml.key?(key) }
+
+        plugin_yaml.merge(common_upstream_values) { |key, plugin_value, upstream_value|
+          if plugin_value.is_a?(Hash) && upstream_value.is_a?(Hash)
+            plugin_value.merge(upstream_value) { |sub_key, plugin_sub_value, upstream_sub_value|
+              if plugin_value.key?(sub_key)
+                plugin_sub_value
+              else
+                upstream_sub_value
+              end
+            }
+          else
+            plugin_value
+          end
+        }
+      end
+    end
+  end
+end

test/standard/plugin_support/merges_upstream_metadata_test.rb

@@ -0,0 +1,67 @@
+require "test_helper"
+
+module Standard
+  module PluginSupport
+    class MergesUpstreamMetadataTest < Minitest::Test
+      def setup
+        @subject = MergesUpstreamMetadata.new
+      end
+
+      def test_no_op
+        assert_equal({}, @subject.merge({}, {}))
+        assert_equal({}, @subject.merge({}, {:junk => {}, "Some/Rule" => {}}))
+        assert_equal({foo: "berry"}, @subject.merge({foo: "berry"}, {:junk => {}, "Some/Rule" => {}}))
+      end
+
+      def test_merges_undefined_sub_keys
+        assert_equal(
+          {"Some/Rule" => {"Enabled" => true, "Description" => "foo"}},
+          @subject.merge(
+            {"Some/Rule" => {"Enabled" => true}},
+            {"Some/Rule" => {"Description" => "foo"}}
+          )
+        )
+      end
+
+      def test_doesnt_merge_nil_values
+        assert_equal(
+          {"Some/Rule" => {"Description" => nil}},
+          @subject.merge(
+            {"Some/Rule" => {"Description" => nil}},
+            {"Some/Rule" => {"Description" => "foo"}}
+          )
+        )
+      end
+
+      def test_doesnt_override_defined_values
+        assert_equal(
+          {"Some/Rule" => {"Enabled" => false}},
+          @subject.merge(
+            {"Some/Rule" => {"Enabled" => false}},
+            {"Some/Rule" => {"Enabled" => true}}
+          )
+        )
+      end
+
+      def test_doesnt_munge_arrays
+        assert_equal(
+          {"Some/Rule" => {"Included" => ["lol"]}},
+          @subject.merge(
+            {"Some/Rule" => {"Included" => ["lol"]}},
+            {"Some/Rule" => {"Included" => ["kek"]}}
+          )
+        )
+      end
+
+      def test_doesnt_munge_hashes
+        assert_equal(
+          {"Some/Rule" => {"Conf" => {a: 1}}},
+          @subject.merge(
+            {"Some/Rule" => {"Conf" => {a: 1}}},
+            {"Some/Rule" => {"Conf" => {a: 2, b: 3}}}
+          )
+        )
+      end
+    end
+  end
+end