Introduce `render :plain` for render plain text

This is as an option to render content with a content type of
`text/plain`. This is the preferred option if you are planning to render
a plain text content.

Please see #12374 for more detail.

1 files changed, 168 insertions, 0 deletions

diff --git a/actionpack/test/controller/new_base/render_plain_test.rb b/actionpack/test/controller/new_base/render_plain_test.rb
new file mode 100644
index 0000000000..dba2e9f13e
--- /dev/null
+++ b/actionpack/test/controller/new_base/render_plain_test.rb
@@ -0,0 +1,168 @@
+require 'abstract_unit'
+
+module RenderPlain
+  class MinimalController < ActionController::Metal
+    include AbstractController::Rendering
+    include ActionController::Rendering
+
+    def index
+      render plain: "Hello World!"
+    end
+  end
+
+  class SimpleController < ActionController::Base
+    self.view_paths = [ActionView::FixtureResolver.new]
+
+    def index
+      render plain: "hello david"
+    end
+  end
+
+  class WithLayoutController < ::ApplicationController
+    self.view_paths = [ActionView::FixtureResolver.new(
+      "layouts/application.text.erb" => "<%= yield %>, I'm here!",
+      "layouts/greetings.text.erb"   => "<%= yield %>, I wish thee well.",
+      "layouts/ivar.text.erb"        => "<%= yield %>, <%= @ivar %>"
+    )]
+
+    def index
+      render plain: "hello david"
+    end
+
+    def custom_code
+      render plain: "hello world", status: 404
+    end
+
+    def with_custom_code_as_string
+      render plain: "hello world", status: "404 Not Found"
+    end
+
+    def with_nil
+      render plain: nil
+    end
+
+    def with_nil_and_status
+      render plain: nil, status: 403
+    end
+
+    def with_false
+      render plain: false
+    end
+
+    def with_layout_true
+      render plain: "hello world", layout: true
+    end
+
+    def with_layout_false
+      render plain: "hello world", layout: false
+    end
+
+    def with_layout_nil
+      render plain: "hello world", layout: nil
+    end
+
+    def with_custom_layout
+      render plain: "hello world", layout: "greetings"
+    end
+
+    def with_ivar_in_layout
+      @ivar = "hello world"
+      render plain: "hello world", layout: "ivar"
+    end
+  end
+
+  class RenderPlainTest < Rack::TestCase
+    test "rendering text from a minimal controller" do
+      get "/render_plain/minimal/index"
+      assert_body "Hello World!"
+      assert_status 200
+    end
+
+    test "rendering text from an action with default options renders the text with the layout" do
+      with_routing do |set|
+        set.draw { get ':controller', action: 'index' }
+
+        get "/render_plain/simple"
+        assert_body "hello david"
+        assert_status 200
+      end
+    end
+
+    test "rendering text from an action with default options renders the text without the layout" do
+      with_routing do |set|
+        set.draw { get ':controller', action: 'index' }
+
+        get "/render_plain/with_layout"
+
+        assert_body "hello david"
+        assert_status 200
+      end
+    end
+
+    test "rendering text, while also providing a custom status code" do
+      get "/render_plain/with_layout/custom_code"
+
+      assert_body "hello world"
+      assert_status 404
+    end
+
+    test "rendering text with nil returns an empty body padded for Safari" do
+      get "/render_plain/with_layout/with_nil"
+
+      assert_body " "
+      assert_status 200
+    end
+
+    test "Rendering text with nil and custom status code returns an empty body padded for Safari and the status" do
+      get "/render_plain/with_layout/with_nil_and_status"
+
+      assert_body " "
+      assert_status 403
+    end
+
+    test "rendering text with false returns the string 'false'" do
+      get "/render_plain/with_layout/with_false"
+
+      assert_body "false"
+      assert_status 200
+    end
+
+    test "rendering text with layout: true" do
+      get "/render_plain/with_layout/with_layout_true"
+
+      assert_body "hello world, I'm here!"
+      assert_status 200
+    end
+
+    test "rendering text with layout: 'greetings'" do
+      get "/render_plain/with_layout/with_custom_layout"
+
+      assert_body "hello world, I wish thee well."
+      assert_status 200
+    end
+
+    test "rendering text with layout: false" do
+      get "/render_plain/with_layout/with_layout_false"
+
+      assert_body "hello world"
+      assert_status 200
+    end
+
+    test "rendering text with layout: nil" do
+      get "/render_plain/with_layout/with_layout_nil"
+
+      assert_body "hello world"
+      assert_status 200
+    end
+
+    test "rendering from minimal controller returns response with text/plain content type" do
+      get "/render_plain/minimal/index"
+      assert_content_type "text/plain"
+    end
+
+    test "rendering from normal controller returns response with text/plain content type" do
+      get "/render_plain/simple/index"
+      assert_content_type "text/plain; charset=utf-8"
+    end
+  end
+end