Add new RSpec/EmptyHook cop

Closes #811

CHANGELOG.md

@@ -7,6 +7,7 @@
 * Ignore String constants by `RSpec/Describe`. ([@AlexWayfer][])
 * Drop support for ruby 2.3. ([@bquorning][])
 * Fix multiple cops to detect `let` with proc argument. ([@tejasbubane][])
+* Add new `RSpec/EmptyHook` cop. ([@tejasbubane][])
 
 ## 1.38.1 (2020-02-15)
 

config/default.yml

@@ -105,6 +105,12 @@ RSpec/EmptyExampleGroup:
   CustomIncludeMethods: []
   StyleGuide: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/EmptyExampleGroup
 
+RSpec/EmptyHook:
+  Description: Checks for empty before and after hooks.
+  Enabled: true
+  VersionAdded: 1.39.0
+  StyleGuide: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/EmptyHook
+
 RSpec/EmptyLineAfterExample:
   Description: Checks if there is an empty line after example blocks.
   Enabled: true

lib/rubocop/cop/rspec/empty_hook.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module RSpec
+      #  Checks for empty before and after hooks.
+      #
+      # @example
+      #   # bad
+      #   before {}
+      #   after do; end
+      #   before(:all) do
+      #   end
+      #   after(:all) { }
+      #
+      #   # good
+      #   before { create_users }
+      #   after do
+      #     cleanup_users
+      #   end
+      #   before(:all) do
+      #     create_feed
+      #   end
+      #   after(:all) { cleanup_feed }
+      class EmptyHook < Cop
+        MSG = 'Empty hook detected.'
+
+        def_node_matcher :empty_hook?, <<~PATTERN
+          (block $#{Hooks::ALL.send_pattern} _ nil?)
+        PATTERN
+
+        def on_block(node)
+          empty_hook?(node) do |hook|
+            add_offense(hook)
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rspec_cops.rb

@@ -30,6 +30,7 @@
 require_relative 'rspec/described_class_module_wrapping'
 require_relative 'rspec/dialect'
 require_relative 'rspec/empty_example_group'
+require_relative 'rspec/empty_hook'
 require_relative 'rspec/empty_line_after_example'
 require_relative 'rspec/empty_line_after_example_group'
 require_relative 'rspec/empty_line_after_final_let'

manual/cops.md

@@ -29,6 +29,7 @@
 * [RSpec/DescribedClassModuleWrapping](cops_rspec.md#rspecdescribedclassmodulewrapping)
 * [RSpec/Dialect](cops_rspec.md#rspecdialect)
 * [RSpec/EmptyExampleGroup](cops_rspec.md#rspecemptyexamplegroup)
+* [RSpec/EmptyHook](cops_rspec.md#rspecemptyhook)
 * [RSpec/EmptyLineAfterExample](cops_rspec.md#rspecemptylineafterexample)
 * [RSpec/EmptyLineAfterExampleGroup](cops_rspec.md#rspecemptylineafterexamplegroup)
 * [RSpec/EmptyLineAfterFinalLet](cops_rspec.md#rspecemptylineafterfinallet)

manual/cops_rspec.md

@@ -639,6 +639,45 @@ CustomIncludeMethods | `[]` | Array
 
 * [https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/EmptyExampleGroup](https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/EmptyExampleGroup)
 
+## RSpec/EmptyHook
+
+Enabled by default | Supports autocorrection
+--- | ---
+Enabled | No
+
+Checks for empty before and after hooks.
+
+### Examples
+
+```ruby
+# bad
+before {}
+after do; end
+before(:all) do
+end
+after(:all) { }
+
+# good
+before { create_users }
+after do
+  cleanup_users
+end
+before(:all) do
+  create_feed
+end
+after(:all) { cleanup_feed }
+```
+
+### Configurable attributes
+
+Name | Default value | Configurable values
+--- | --- | ---
+VersionAdded | `1.39.0` | String
+
+### References
+
+* [https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/EmptyHook](https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/EmptyHook)
+
 ## RSpec/EmptyLineAfterExample
 
 Enabled by default | Supports autocorrection

spec/rubocop/cop/rspec/empty_hook_spec.rb

@@ -0,0 +1,208 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::RSpec::EmptyHook do
+  subject(:cop) { described_class.new }
+
+  context 'with `before` hook' do
+    it 'detects offense for empty `before`' do
+      expect_offense(<<~RUBY)
+        before {}
+        ^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'detects offense for empty `before` with :each scope' do
+      expect_offense(<<~RUBY)
+        before(:each) {}
+        ^^^^^^^^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'detects offense for empty `before` with :example scope' do
+      expect_offense(<<~RUBY)
+        before(:example) {}
+        ^^^^^^^^^^^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'detects offense for empty `before` with :context scope' do
+      expect_offense(<<~RUBY)
+        before(:context) {}
+        ^^^^^^^^^^^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'detects offense for empty `before` with :all scope' do
+      expect_offense(<<~RUBY)
+        before(:all) {}
+        ^^^^^^^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'detects offense for empty `before` with :suite scope' do
+      expect_offense(<<~RUBY)
+        before(:suite) {}
+        ^^^^^^^^^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'accepts non-empty `before` hook' do
+      expect_no_offenses(<<~RUBY)
+        before { create_users }
+      RUBY
+    end
+
+    it 'accepts multiline `before` hook' do
+      expect_no_offenses(<<~RUBY)
+        before(:all) do
+          create_users
+          create_products
+        end
+      RUBY
+    end
+  end
+
+  context 'with `after` hook' do
+    it 'detects offense for empty `after`' do
+      expect_offense(<<~RUBY)
+        after {}
+        ^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'accepts non-empty `after` hook' do
+      expect_no_offenses(<<~RUBY)
+        after { cleanup_users }
+      RUBY
+    end
+
+    it 'accepts multiline `after` hook' do
+      expect_no_offenses(<<~RUBY)
+        after(:suite) do
+          cleanup_users
+          cleanup_products
+        end
+      RUBY
+    end
+  end
+
+  context 'with `around` hook' do
+    it 'detects offense for empty `around`' do
+      expect_offense(<<~RUBY)
+        around {}
+        ^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'accepts non-empty `around` hook' do
+      expect_no_offenses(<<~RUBY)
+        around { yield }
+      RUBY
+    end
+
+    it 'accepts multiline `around` hook' do
+      expect_no_offenses(<<~RUBY)
+        around(:suite) do
+          setup_users
+          yield
+        end
+      RUBY
+    end
+  end
+
+  context 'with `prepend_before` hook' do
+    it 'detects offense for empty `prepend_before`' do
+      expect_offense(<<~RUBY)
+        prepend_before {}
+        ^^^^^^^^^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'accepts non-empty `prepend_before` hook' do
+      expect_no_offenses(<<~RUBY)
+        prepend_before { create_users }
+      RUBY
+    end
+
+    it 'accepts multiline `prepend_before` hook' do
+      expect_no_offenses(<<~RUBY)
+        prepend_before(:all) do
+          create_users
+          create_products
+        end
+      RUBY
+    end
+  end
+
+  context 'with `append_before` hook' do
+    it 'detects offense for empty `append_before`' do
+      expect_offense(<<~RUBY)
+        append_before {}
+        ^^^^^^^^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'accepts non-empty `append_before` hook' do
+      expect_no_offenses(<<~RUBY)
+        append_before { create_users }
+      RUBY
+    end
+
+    it 'accepts multiline `append_before` hook' do
+      expect_no_offenses(<<~RUBY)
+        append_before(:each) do
+          create_users
+          create_products
+        end
+      RUBY
+    end
+  end
+
+  context 'with `prepend_after` hook' do
+    it 'detects offense for empty `prepend_after`' do
+      expect_offense(<<~RUBY)
+        prepend_after {}
+        ^^^^^^^^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'accepts non-empty `prepend_after` hook' do
+      expect_no_offenses(<<~RUBY)
+        prepend_after { cleanup_users }
+      RUBY
+    end
+
+    it 'accepts multiline `prepend_after` hook' do
+      expect_no_offenses(<<~RUBY)
+        prepend_after(:all) do
+          cleanup_users
+          cleanup_products
+        end
+      RUBY
+    end
+  end
+
+  context 'with `append_after` hook' do
+    it 'detects offense for empty `append_after`' do
+      expect_offense(<<~RUBY)
+        append_after {}
+        ^^^^^^^^^^^^ Empty hook detected.
+      RUBY
+    end
+
+    it 'accepts non-empty `append_after` hook' do
+      expect_no_offenses(<<~RUBY)
+        append_after { cleanup_users }
+      RUBY
+    end
+
+    it 'accepts multiline `append_after` hook' do
+      expect_no_offenses(<<~RUBY)
+        append_after(:all) do
+          cleanup_users
+          cleanup_products
+        end
+      RUBY
+    end
+  end
+end