Add new Rails/RenderInline cop

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### New features
 
+* [#271](https://github.com/rubocop-hq/rubocop-rails/pull/271): Add new `Rails/RenderInline` cop. ([@fatkodima][])
 * [#281](https://github.com/rubocop-hq/rubocop-rails/pull/281): Add new `Rails/MailerName` cop. ([@fatkodima][])
 * [#246](https://github.com/rubocop-hq/rubocop-rails/issues/246): Add new `Rails/PluckInWhere` cop. ([@fatkodima][])
 * [#17](https://github.com/rubocop-hq/rubocop-rails/issues/17): Add new `Rails/NegateInclude` cop. ([@fatkodima][])

config/default.yml

@@ -465,6 +465,12 @@ Rails/RelativeDateConstant:
   VersionChanged: '0.59'
   AutoCorrect: false
 
+Rails/RenderInline:
+  Description: 'Prefer using a template over inline rendering.'
+  StyleGuide: 'https://rails.rubystyle.guide/#inline-rendering'
+  Enabled: 'pending'
+  VersionAdded: '2.7'
+
 Rails/RequestReferer:
   Description: 'Use consistent syntax for request.referer.'
   Enabled: true

docs/modules/ROOT/pages/cops.adoc

@@ -57,6 +57,7 @@
 * xref:cops_rails.adoc#railsreflectionclassname[Rails/ReflectionClassName]
 * xref:cops_rails.adoc#railsrefutemethods[Rails/RefuteMethods]
 * xref:cops_rails.adoc#railsrelativedateconstant[Rails/RelativeDateConstant]
+* xref:cops_rails.adoc#railsrenderinline[Rails/RenderInline]
 * xref:cops_rails.adoc#railsrequestreferer[Rails/RequestReferer]
 * xref:cops_rails.adoc#railsreversiblemigration[Rails/ReversibleMigration]
 * xref:cops_rails.adoc#railssafenavigation[Rails/SafeNavigation]

docs/modules/ROOT/pages/cops_rails.adoc

@@ -2779,6 +2779,47 @@ end
 | Boolean
 |===
 
+== Rails/RenderInline
+
+|===
+| Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
+
+| Pending
+| Yes
+| No
+| 2.7
+| -
+|===
+
+This cop looks for inline rendering within controller actions.
+
+=== Examples
+
+[source,ruby]
+----
+# bad
+class ProductsController < ApplicationController
+  def index
+    render inline: "<% products.each do |p| %><p><%= p.name %></p><% end %>", type: :erb
+  end
+end
+
+# good
+# app/views/products/index.html.erb
+# <% products.each do |p| %>
+#   <p><%= p.name %></p>
+# <% end %>
+
+class ProductsController < ApplicationController
+  def index
+  end
+end
+----
+
+=== References
+
+* https://rails.rubystyle.guide/#inline-rendering
+
 == Rails/RequestReferer
 
 |===

lib/rubocop/cop/rails/render_inline.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Rails
+      # This cop looks for inline rendering within controller actions.
+      #
+      # @example
+      #   # bad
+      #   class ProductsController < ApplicationController
+      #     def index
+      #       render inline: "<% products.each do |p| %><p><%= p.name %></p><% end %>", type: :erb
+      #     end
+      #   end
+      #
+      #   # good
+      #   # app/views/products/index.html.erb
+      #   # <% products.each do |p| %>
+      #   #   <p><%= p.name %></p>
+      #   # <% end %>
+      #
+      #   class ProductsController < ApplicationController
+      #     def index
+      #     end
+      #   end
+      #
+      class RenderInline < Cop
+        MSG = 'Prefer using a template over inline rendering.'
+
+        def_node_matcher :render_with_options?, <<~PATTERN
+          (send nil? :render $(hash ...))
+        PATTERN
+
+        def on_send(node)
+          render_with_options?(node) do |options|
+            add_offense(node) if includes_inline_key?(options)
+          end
+        end
+
+        private
+
+        def includes_inline_key?(node)
+          node.keys.find { |key| key.value.to_sym == :inline }
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rails_cops.rb

@@ -59,6 +59,7 @@
 require_relative 'rails/reflection_class_name'
 require_relative 'rails/refute_methods'
 require_relative 'rails/relative_date_constant'
+require_relative 'rails/render_inline'
 require_relative 'rails/request_referer'
 require_relative 'rails/reversible_migration'
 require_relative 'rails/safe_navigation'

spec/rubocop/cop/rails/render_inline_spec.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Rails::RenderInline do
+  subject(:cop) { described_class.new }
+
+  it 'registers an offense when rendering inline with a symbol key' do
+    expect_offense(<<~RUBY)
+      render status: 200, inline: 'inline template'
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using a template over inline rendering.
+    RUBY
+  end
+
+  it 'registers an offense when rendering inline with a string key' do
+    expect_offense(<<~RUBY)
+      render status: 200, 'inline' => 'inline template'
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using a template over inline rendering.
+    RUBY
+  end
+
+  it 'does not register an offense when rendering a template' do
+    expect_no_offenses(<<~RUBY)
+      render :index
+    RUBY
+  end
+end