Introduce FactoryGirl/FactoryClassName cop

The cop ensures that when creating factories, we do not allow
passing the class itself. Instead we require users to pass the
class name.

Although `FactoryBot` allows passing the class, we find that by doing so,
application models are loaded during application initialization and
many files are required without them having to.

This affects the startup time as well as libraries like simplecov
that fail to capture those files.

Example:

bad
```
factory :foo, class: Foo do
end
```

good
```
factory :foo, class: 'Foo' do
end
```

Author: fragoulis

CHANGELOG.md

@@ -7,6 +7,7 @@
 * Fix `RSpec/SubjectStub` to detect implicit subjects stubbed. ([@QQism][])
 * Fix `RSpec/Pending` not flagging `skip` with string values. ([@pirj][])
 * Add `AllowedExplicitMatchers` config option for `RSpec/PredicateMatcher`. ([@mkrawc][])
+* Add `FactoryBot/FactoryClassName` cop. ([@jfragoulis][])
 
 ## 1.36.0 (2019-09-27)
 
@@ -462,3 +463,4 @@ Compatibility release so users can upgrade RuboCop to 0.51.0. No new features.
 [@QQism]: https://github.com/QQism
 [@kellysutton]: https://github.com/kellysutton
 [@mkrawc]: https://github.com/mkrawc
+[@jfragoulis]: https://github.com/jfragoulis

config/default.yml

@@ -480,6 +480,11 @@ FactoryBot/CreateList:
   - n_times
   StyleGuide: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/FactoryBot/CreateList
 
+FactoryBot/FactoryClassName:
+  Description: Use string value when setting the class attribute explicitly.
+  Enabled: true
+  StyleGuide: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/FactoryBot/FactoryClassName
+
 Rails/HttpStatus:
   Description: Enforces use of symbolic or numeric value to describe HTTP status.
   Enabled: true

lib/rubocop/cop/rspec/factory_bot/factory_class_name.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module RSpec
+      module FactoryBot
+        # Use string value when setting the class attribute explicitly.
+        #
+        # @example
+        #   # bad
+        #   factory :foo, class: Foo do
+        #   end
+        #
+        #   # good
+        #   factory :foo, class: 'Foo' do
+        #   end
+        class FactoryClassName < Cop
+          MSG = "Pass '%<class_name>s' instead of %<class_name>s."
+
+          def_node_matcher :class_name, <<~PATTERN
+            (send _ :factory _ (hash <(pair (sym :class) $(const ...)) ...>))
+          PATTERN
+
+          def on_send(node)
+            class_name(node) do |cn|
+              add_offense(cn, message: format(MSG, class_name: cn.const_name))
+            end
+          end
+
+          def autocorrect(node)
+            lambda do |corrector|
+              corrector.replace(node.loc.expression, "'#{node.source}'")
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rspec_cops.rb

@@ -5,6 +5,7 @@
 
 require_relative 'rspec/factory_bot/attribute_defined_statically'
 require_relative 'rspec/factory_bot/create_list'
+require_relative 'rspec/factory_bot/factory_class_name'
 
 begin
   require_relative 'rspec/rails/http_status'

manual/cops.md

@@ -8,6 +8,7 @@
 
 * [FactoryBot/AttributeDefinedStatically](cops_factorybot.md#factorybotattributedefinedstatically)
 * [FactoryBot/CreateList](cops_factorybot.md#factorybotcreatelist)
+* [FactoryBot/FactoryClassName](cops_factorybot.md#factorybotfactoryclassname)
 
 #### Department [RSpec](cops_rspec.md)
 

manual/cops_factorybot.md

@@ -77,3 +77,27 @@ EnforcedStyle | `create_list` | `create_list`, `n_times`
 ### References
 
 * [https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/FactoryBot/CreateList](https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/FactoryBot/CreateList)
+
+## FactoryBot/FactoryClassName
+
+Enabled by default | Supports autocorrection
+--- | ---
+Enabled | Yes
+
+Use string value when setting the class attribute explicitly.
+
+### Examples
+
+```ruby
+# bad
+factory :foo, class: Foo do
+end
+
+# good
+factory :foo, class: 'Foo' do
+end
+```
+
+### References
+
+* [https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/FactoryBot/FactoryClassName](https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/FactoryBot/FactoryClassName)

spec/rubocop/cop/rspec/factory_bot/factory_class_name_spec.rb

@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::RSpec::FactoryBot::FactoryClassName do
+  subject(:cop) { described_class.new }
+
+  context 'when passing block' do
+    it 'flags passing a class' do
+      expect_offense(<<~RUBY)
+        factory :foo, class: Foo do
+                             ^^^ Pass 'Foo' instead of Foo.
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        factory :foo, class: 'Foo' do
+        end
+      RUBY
+    end
+
+    it 'flags passing a class from global namespace' do
+      expect_offense(<<~RUBY)
+        factory :foo, class: ::Foo do
+                             ^^^^^ Pass 'Foo' instead of Foo.
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        factory :foo, class: '::Foo' do
+        end
+      RUBY
+    end
+
+    it 'flags passing a subclass' do
+      expect_offense(<<~RUBY)
+        factory :foo, class: Foo::Bar do
+                             ^^^^^^^^ Pass 'Foo::Bar' instead of Foo::Bar.
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        factory :foo, class: 'Foo::Bar' do
+        end
+      RUBY
+    end
+
+    it 'ignores passing class name' do
+      expect_no_offenses(<<~RUBY)
+        factory :foo, class: 'Foo' do
+        end
+      RUBY
+    end
+  end
+
+  context 'when not passing block' do
+    it 'flags passing a class' do
+      expect_offense(<<~RUBY)
+        factory :foo, class: Foo
+                             ^^^ Pass 'Foo' instead of Foo.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        factory :foo, class: 'Foo'
+      RUBY
+    end
+
+    it 'ignores passing class name' do
+      expect_no_offenses(<<~RUBY)
+        factory :foo, class: 'Foo'
+      RUBY
+    end
+  end
+end