Introduce BundlerSetupInTests cop

config/default.yml

@@ -1,5 +1,10 @@
 # This is the default configuration file.
 
+Packaging/BundlerSetupInTests:
+  Description: 'Avoid using `bundler/setup` in your tests.'
+  Enabled: true
+  VersionAdded: '0.4'
+
 Packaging/GemspecGit:
   Description: 'Use pure Ruby alternative instead of `git ls-files`.'
   Enabled: true

docs/modules/ROOT/pages/cops.adoc

@@ -2,6 +2,7 @@
 
 === Department xref:cops_packaging.adoc[Packaging]
 
+* xref:cops_packaging.adoc#packagingbundlersetupintests[Packaging/BundlerSetupInTests]
 * xref:cops_packaging.adoc#packaginggemspecgit[Packaging/GemspecGit]
 * xref:cops_packaging.adoc#packagingrequirerelativehardcodinglib[Packaging/RequireRelativeHardcodingLib]
 

docs/modules/ROOT/pages/cops_packaging.adoc

@@ -1,5 +1,32 @@
 = Packaging
 
+== Packaging/BundlerSetupInTests
+
+|===
+| Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
+
+| Enabled
+| Yes
+| No
+| 0.4
+| -
+|===
+
+This cop flags the `require "bundler/setup"` calls if they're
+made from inside the tests directory.
+
+=== Examples
+
+[source,ruby]
+----
+# bad
+require "foo"
+require "bundler/setup"
+
+# good
+require "foo"
+----
+
 == Packaging/GemspecGit
 
 |===

lib/rubocop/cop/packaging/bundler_setup_in_tests.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+require "rubocop/packaging/lib_helper_module"
+
+module RuboCop # :nodoc:
+  module Cop # :nodoc:
+    module Packaging # :nodoc:
+      # This cop flags the `require "bundler/setup"` calls if they're
+      # made from inside the tests directory.
+      #
+      # @example
+      #
+      #   # bad
+      #   require "foo"
+      #   require "bundler/setup"
+      #
+      #   # good
+      #   require "foo"
+      #
+      class BundlerSetupInTests < Base
+        include RuboCop::Packaging::LibHelperModule
+
+        # This is the message that will be displayed when RuboCop::Packaging finds
+        # an offense of using `require "bundler/setup"` in the tests directory.
+        MSG = "Avoid using `bundler/setup` in your tests."
+
+        def_node_matcher :bundler_setup?, <<~PATTERN
+          (send nil? :require
+            (str #bundler_setup_in_test_dir?))
+        PATTERN
+
+        # Extended from the Base class.
+        # More about the `#on_new_investigation` method can be found here:
+        # https://github.com/rubocop-hq/rubocop/blob/343f62e4555be0470326f47af219689e21c61a37/lib/rubocop/cop/base.rb
+        #
+        # Processing of the AST happens here.
+        def on_new_investigation
+          @file_path = processed_source.file_path
+          @file_directory = File.dirname(@file_path)
+        end
+
+        # Extended from AST::Traversal.
+        # More about the `#on_send` method can be found here:
+        # https://github.com/rubocop-hq/rubocop-ast/blob/08d0f49a47af1e9a30a6d8f67533ba793c843d67/lib/rubocop/ast/traversal.rb#L112
+        def on_send(node)
+          return unless bundler_setup?(node)
+
+          add_offense(node)
+        end
+
+        # This method is called from inside `#def_node_matcher`.
+        # It flags an offense if the `require "bundler/setup"`
+        # call is made from the tests directory.
+        def bundler_setup_in_test_dir?(str)
+          str.eql?("bundler/setup") && falls_in_test_dir?
+        end
+
+        # This method determines if the call is made *from* the tests directory.
+        def falls_in_test_dir?
+          %w[spec specs test tests].any? { |dir| File.expand_path(@file_directory).start_with?("#{root_dir}/#{dir}") }
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/packaging_cops.rb

@@ -1,4 +1,5 @@
 # frozen_string_literal: true
 
+require_relative "packaging/bundler_setup_in_tests"
 require_relative "packaging/gemspec_git"
 require_relative "packaging/require_relative_hardcoding_lib"

spec/rubocop/cop/packaging/bundler_setup_in_tests_spec.rb

@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Packaging::BundlerSetupInTests, :config do
+  let(:message) { RuboCop::Cop::Packaging::BundlerSetupInTests::MSG }
+
+  let(:project_root) { RuboCop::ConfigLoader.project_root }
+
+  context "when `require bundler/setup` is used in specs/" do
+    let(:filename) { "#{project_root}/spec/spec_helper.rb" }
+    let(:source) { "require 'bundler/setup'" }
+
+    it "registers an offense" do
+      expect_offense(<<~RUBY, filename)
+        #{source}
+        #{"^" * source.length} #{message}
+      RUBY
+    end
+  end
+
+  context "when `require bundler/setup` is used in test/foo" do
+    let(:filename) { "#{project_root}/tests/foo/test_bar.rb" }
+    let(:source) { "require 'bundler/setup'" }
+
+    it "registers an offense" do
+      expect_offense(<<~RUBY, filename)
+        #{source}
+        #{"^" * source.length} #{message}
+      RUBY
+    end
+  end
+
+  context "when `require bundler/setup` is used in a Rakefile" do
+    let(:filename) { "#{project_root}/Rakefile" }
+    let(:source) { "require 'bundler/setup'" }
+
+    it "does not register an offense" do
+      expect_no_offenses(<<~RUBY, filename)
+        #{source}
+      RUBY
+    end
+  end
+
+  context "when `require bundler/setup` is used in bin/console" do
+    let(:filename) { "#{project_root}/bin/console" }
+    let(:source) { "require 'bundler/setup'" }
+
+    it "does not register an offense" do
+      expect_no_offenses(<<~RUBY, filename)
+        #{source}
+      RUBY
+    end
+  end
+end