[Fix rubocop#36] Rake/Desc should not generate offense for prerequi…

…site declarations

Closes rubocop#36

CHANGELOG.md

@@ -7,6 +7,7 @@
 * [#33](https://github.com/rubocop/rubocop-rake/pull/33): Drop support for Ruby 2.3. ([@koic][])
 * [#34](https://github.com/rubocop/rubocop-rake/pull/34): Require RuboCop 1.0 or higher. ([@koic][])
 * [#38](https://github.com/rubocop/rubocop-rake/pull/37): Drop support for Ruby 2.4. ([@tejasbubane])
+* [#36](https://github.com/rubocop/rubocop-rake/issues/36): Fix `Rake/Desc` to not generate offense for prerequisite declarations. ([@tejasbubane][])
 
 ## 0.5.1 (2020-02-14)
 

lib/rubocop/cop/rake/desc.rb

@@ -33,10 +33,17 @@ class Desc < Base
 
         MSG = 'Describe the task with `desc` method.'
 
+        def_node_matcher :prerequisites, <<~PATTERN
+          (send nil? :task (hash (pair _ $_)))
+        PATTERN
+
         def on_task(node)
           return if task_with_desc?(node)
           return if Helper::TaskName.task_name(node) == :default
 
+          requirements = prerequisites(node)
+          return if requirements && requirements.array_type?
+
           add_offense(node)
         end
 

spec/rubocop/cop/rake/desc_spec.rb

@@ -63,4 +63,17 @@
       task.name
     RUBY
   end
+
+  it 'registers an offense for one prerequisite declaration (alias)' do
+    expect_offense(<<~RUBY)
+      task release: 'changelog:check_clean'
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Describe the task with `desc` method.
+    RUBY
+  end
+
+  it 'does not register an offense for multiple prerequisite declarations' do
+    expect_no_offenses(<<~RUBY)
+      task release: ['changelog:check_clean', 'changelog:create']
+    RUBY
+  end
 end