Allow inclusion of custom rules (#6)

* Fix up some CC issues

* Allow configurable custom rules via config file

* Document `include_rules` usage in README

Author: toddmohney

README.md

@@ -14,8 +14,8 @@ engines:
 
 ## Configuration
 
-This engine accepts `tags` and `cookbook_paths` in its configuration. Both
-values are optional:
+This engine accepts `tags`, `cookbook_paths` and `include_rules` in its
+configuration. All values are optional:
 
 ```yml
 engines:
@@ -28,6 +28,9 @@ engines:
       cookbook_paths:
       - libraries/mysql.rb
       - libraries/docker.rb
+      include_rules:
+      - rules/my_custom_rule.rb
+      - rules/my_other_custom_rule.rb
 ```
 
 **NOTE**: `cookbook_paths`, when defined, are passed directly to Foodcritic and

lib/cc/engine.rb

@@ -7,15 +7,16 @@ module Engine
     def self.each_issue
       rules = Rules.new
 
-      get_warnings.each do |lint|
+      warnings.each do |lint|
         yield Issue.new(lint, rules)
       end
     end
 
-    def self.get_warnings
+    def self.warnings
       config = Config.new
       options = {
         cookbook_paths: config.cookbook_paths,
+        include_rules: config.include_rules,
         progress: false,
         tags: config.tags,
       }
@@ -30,7 +31,7 @@ class Config
       DEFAULT_TAGS = ["~FC011", "~FC033"]
 
       def initialize(path = "/config.json")
-        if File.exists?(path)
+        if File.exist?(path)
           @config = JSON.parse(File.read(path))
         else
           @config = {}
@@ -41,6 +42,10 @@ def cookbook_paths
         engine_config.fetch("cookbook_paths") { expand_include_paths }
       end
 
+      def include_rules
+        engine_config.fetch("include_rules", [])
+      end
+
       def tags
         engine_config.fetch("tags", DEFAULT_TAGS)
       end
@@ -69,7 +74,7 @@ def expand_include_paths
 
     class Rules
       def initialize(path = "/rules.yml")
-        if File.exists?(path)
+        if File.exist?(path)
           @config = YAML.load_file(path)
         else
           @config = {}

spec/cc/engine_spec.rb

@@ -57,6 +57,23 @@ module CC
         end
       end
 
+      describe "#include_rules" do
+        it "provides a default" do
+          config = Engine::Config.new
+          expect(config.include_rules).to(eq([]))
+        end
+
+        it "allows overrides via config" do
+          Tempfile.open("config.json") do |tmp|
+            tmp.write(%{ {"config":{"include_rules":["some_rule.rb","some_other_rule.rb"]}} })
+            tmp.rewind
+
+            config = Engine::Config.new(tmp.path)
+            expect(config.include_rules).to eq %w[some_rule.rb some_other_rule.rb]
+          end
+        end
+      end
+
       describe "#tags" do
         it "has a sane default" do
           config = Engine::Config.new