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

…site declarations

Closes rubocop#36

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 * [#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][])
+* [#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)
 
@@ -57,3 +58,4 @@
 [@pocke]: https://github.com/pocke
 [@jaruuuu]: https://github.com/jaruuuu
 [@koic]: https://github.com/koic
+[@tejasbubane]: https://github.com/tejasbubane

lib/rubocop/cop/rake/desc.rb

@@ -33,9 +33,14 @@ class Desc < Base
 
         MSG = 'Describe the task with `desc` method.'
 
+        def_node_matcher :prerequisite_declaration?, <<~PATTERN
+          (send nil? :task (hash ...))
+        PATTERN
+
         def on_task(node)
           return if task_with_desc?(node)
           return if Helper::TaskName.task_name(node) == :default
+          return if prerequisite_declaration?(node)
 
           add_offense(node)
         end

spec/rubocop/cop/rake/desc_spec.rb

@@ -63,4 +63,10 @@
       task.name
     RUBY
   end
+
+  it 'does not register an offense for prerequisite declarations' do
+    expect_no_offenses(<<~RUBY)
+      task release: 'changelog:check_clean'
+    RUBY
+  end
 end