Add ScatteredSetup cop

config/default.yml

@@ -137,6 +137,10 @@ RSpec/NotToNot:
   - to_not
   Enabled: true
 
+RSpec/ScatteredSetup:
+  Description: Checks for separated hooks in the same example group.
+  Enabled: true
+
 RSpec/SubjectStub:
   Description: Checks for stubbed test subjects.
   Enabled: true

lib/rubocop-rspec.rb

@@ -40,5 +40,6 @@
 require 'rubocop/cop/rspec/named_subject'
 require 'rubocop/cop/rspec/nested_groups'
 require 'rubocop/cop/rspec/not_to_not'
+require 'rubocop/cop/rspec/scattered_setup'
 require 'rubocop/cop/rspec/subject_stub'
 require 'rubocop/cop/rspec/verified_doubles'

lib/rubocop/cop/rspec/scattered_setup.rb

@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module RSpec
+      # Checks for separated hooks in the same example group.
+      #
+      # Unify `before`, `after`, and `around` hooks when possible.
+      #
+      # @example
+      #   # bad
+      #   describe Foo do
+      #     before { setup1 }
+      #     before { setup2 }
+      #   end
+      #
+      #   # good
+      #   describe Foo do
+      #     before do
+      #       setup1
+      #       setup2
+      #     end
+      #   end
+      #
+      class ScatteredSetup < Cop
+        include RuboCop::RSpec::TopLevelDescribe
+
+        MSG = 'Do not define multiple hooks in the same example group.'.freeze
+
+        # Selectors which indicate that indicate we should stop searching
+        # for more hook definitions
+        SCOPE_CHANGES = ExampleGroups::ALL + SharedGroups::ALL + Examples::ALL
+
+        # @!method hook(node)
+        #
+        #   Detect if node is `before`, `after`, `around`
+        def_node_matcher :hook, <<-PATTERN
+        (block $(send nil {#{Hooks::ALL.to_node_pattern}} ...) ...)
+        PATTERN
+
+        # @!method scope_change?(node)
+        #
+        #   Detect if the node is an example or a new example group
+        #
+        def_node_matcher :scope_change?, <<-PATTERN
+          (block (send _ {#{SCOPE_CHANGES.to_node_pattern}} ...) ...)
+        PATTERN
+
+        def on_block(node)
+          return unless example_group?(node)
+
+          repeated =
+            hooks_in_group(node)
+              .group_by(&:method_name)
+              .values
+              .reject(&:one?)
+              .flatten
+
+          repeated.each do |repeated_hook|
+            add_offense(repeated_hook, :expression)
+          end
+        end
+
+        def hooks_in_group(node, &block)
+          return to_enum(__method__, node) unless block_given?
+
+          node.each_child_node { |child| find_hooks(child, &block) }
+        end
+
+        def find_hooks(node, &block)
+          return if scope_change?(node)
+
+          hook(node, &block)
+          hooks_in_group(node, &block)
+        end
+      end
+    end
+  end
+end

spec/rubocop/cop/rspec/scattered_setup_spec.rb

@@ -0,0 +1,62 @@
+describe RuboCop::Cop::RSpec::ScatteredSetup do
+  subject(:cop) { described_class.new }
+
+  it 'flags multiple hooks in the same example group' do
+    expect_violation(<<-RUBY)
+      describe Foo do
+        before { bar }
+        ^^^^^^ Do not define multiple hooks in the same example group.
+        before { baz }
+        ^^^^^^ Do not define multiple hooks in the same example group.
+      end
+    RUBY
+  end
+
+  it 'does not flag different hooks' do
+    expect_no_violations(<<-RUBY)
+      describe Foo do
+        before { bar }
+        after { baz }
+        around { qux }
+      end
+    RUBY
+  end
+
+  it 'does not flag hooks in different example groups' do
+    expect_no_violations(<<-RUBY)
+      describe Foo do
+        before { bar }
+
+        describe '.baz' do
+          before { baz }
+        end
+      end
+    RUBY
+  end
+
+  it 'does not flag hooks in different shared contexts' do
+    expect_no_violations(<<-RUBY)
+      describe Foo do
+        shared_context 'one' do
+          before { bar }
+        end
+
+        shared_context 'two' do
+          before { baz }
+        end
+      end
+    RUBY
+  end
+
+  it 'does not flag similar method names inside of examples' do
+    expect_no_violations(<<-RUBY)
+      describe Foo do
+        before { bar }
+
+        it 'uses an instance method called before' do
+          expect(before { tricky }).to_not confuse_rubocop_rspec
+        end
+      end
+    RUBY
+  end
+end