Check for unneeded directives when all other rules are done

spec/ameba/base_spec.cr

@@ -14,10 +14,6 @@ module Ameba::Rule
         rules.should contain DummyRule
         rules.should contain NoProperties
       end
-
-      it "should not include syntax rule" do
-        Rule.rules.should_not contain Rule::Syntax
-      end
     end
 
     context "properties" do

spec/ameba/config_spec.cr

@@ -66,14 +66,14 @@ module Ameba
       config = Config.load config_sample
 
       it "updates enabled property" do
-        name = DummyRule.class_name
+        name = DummyRule.rule_name
         config.update_rule name, enabled: false
         rule = config.rules.find(&.name.== name).not_nil!
         rule.enabled.should be_false
       end
 
       it "updates excluded property" do
-        name = DummyRule.class_name
+        name = DummyRule.rule_name
         excluded = %w(spec/source.cr)
         config.update_rule name, excluded: excluded
         rule = config.rules.find(&.name.== name).not_nil!

spec/ameba/formatter/todo_formatter_spec.cr

@@ -44,7 +44,7 @@ module Ameba
       end
 
       it "creates a todo with run details" do
-        create_todo.should contain "Run `ameba --only #{DummyRule.class_name}`"
+        create_todo.should contain "Run `ameba --only #{DummyRule.rule_name}`"
       end
 
       it "excludes source from this rule" do

spec/ameba/rule/unneded_disable_directive_spec.cr

@@ -67,7 +67,7 @@ module Ameba::Rule
 
     it "fails if there is disabled UnneededDisableDirective" do
       s = Source.new %Q(
-        # ameba:disable #{UnneededDisableDirective.class_name}
+        # ameba:disable #{UnneededDisableDirective.rule_name}
         a = 1
       ), "source.cr"
       s.error UnneededDisableDirective.new, 3, 1, "Alarm!", :disabled

spec/ameba/runner_spec.cr

@@ -6,7 +6,7 @@ module Ameba
     config.formatter = formatter
     config.files = files
 
-    config.update_rule ErrorRule.class_name, enabled: false
+    config.update_rule ErrorRule.rule_name, enabled: false
 
     Runner.new(config)
   end
@@ -59,7 +59,7 @@ module Ameba
 
           Runner.new(rules, [source], formatter).run
           source.should_not be_valid
-          source.errors.first.rule.name.should eq "Syntax"
+          source.errors.first.rule.name.should eq Rule::Syntax.rule_name
         end
 
         it "does not run other rules" do
@@ -75,6 +75,19 @@ module Ameba
           source.errors.size.should eq 1
         end
       end
+
+      context "unneeded disables" do
+        it "reports an error if such disable exists" do
+          rules = [Rule::UnneededDisableDirective.new] of Rule::Base
+          source = Source.new %(
+            a = 1 # ameba:disable LineLength
+          )
+
+          Runner.new(rules, [source], formatter).run
+          source.should_not be_valid
+          source.errors.first.rule.name.should eq Rule::UnneededDisableDirective.rule_name
+        end
+      end
     end
 
     describe "#success?" do

src/ameba/config.cr

@@ -186,7 +186,7 @@ class Ameba::Config
 
         def self.new(config = nil)
           if (raw = config.try &.raw).is_a? Hash
-            yaml = raw[class_name]?.try &.to_yaml
+            yaml = raw[rule_name]?.try &.to_yaml
           end
           from_yaml yaml || "{}"
         end

src/ameba/rule/base.cr

@@ -1,7 +1,9 @@
 module Ameba::Rule
+  # List of names of the special rules, which
+  # behave differently than usual rules.
   SPECIAL = [
-    Syntax.class_name,
+    Syntax.rule_name,
-    UnneededDisableDirective.class_name,
+    UnneededDisableDirective.rule_name,
   ]
 
   # Represents a base of all rules. In other words, all rules
@@ -60,7 +62,7 @@ module Ameba::Rule
     # ```
     #
     def name
-      {{@type}}.class_name
+      {{@type}}.rule_name
     end
 
     # Checks whether the source is excluded from this rule.
@@ -78,7 +80,18 @@ module Ameba::Rule
       end
     end
 
-    protected def self.class_name
+    # Returns true if this rule is special and behaves differently than
+    # usual rules.
+    #
+    # ```
+    # my_rule.special? # => true or false
+    # ```
+    #
+    def special?
+      SPECIAL.includes? name
+    end
+
+    protected def self.rule_name
       name.gsub("Ameba::Rule::", "")
     end
 
@@ -95,6 +108,6 @@ module Ameba::Rule
   # ```
   #
   def self.rules
-    Base.subclasses.reject! &.== Rule::Syntax
+    Base.subclasses
   end
 end

src/ameba/runner.cr

@@ -23,6 +23,9 @@ module Ameba
     # A syntax rule which always inspects a source first
     @syntax_rule = Rule::Syntax.new
 
+    # Checks for unneeded disable directives. Always inspects a source last
+    @unneeded_disable_directive_rule : Rule::Base?
+
     # Instantiates a runner using a `config`.
     #
     # ```
@@ -36,7 +39,11 @@ module Ameba
     def initialize(config : Config)
       @sources = load_sources(config)
       @formatter = config.formatter
-      @rules = config.rules.select &.enabled
+      @rules = config.rules.select(&.enabled).reject!(&.special?)
+
+      @unneeded_disable_directive_rule =
+        config.rules
+              .find &.name.==(Rule::UnneededDisableDirective.rule_name)
     end
 
     # :nodoc:
@@ -65,6 +72,7 @@ module Ameba
             next if rule.excluded?(source)
             rule.test(source)
           end
+          check_unneeded_directives(source)
         end
 
         @formatter.source_finished source
@@ -87,6 +95,12 @@ module Ameba
       @sources.all? &.valid?
     end
 
+    private def check_unneeded_directives(source)
+      if (rule = @unneeded_disable_directive_rule) && rule.enabled
+        rule.test(source)
+      end
+    end
+
     private def load_sources(config)
       config.files.map do |wildcard|
         wildcard += "/**/*.cr" if File.directory?(wildcard)