Add deprecation warning for `render :text`

We've started on discouraging the usage of `render :text` in #12374.
This is a follow-up commit to make sure that we print out the
deprecation warning.

1 files changed, 14 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller/metal/rendering.rb b/actionpack/lib/action_controller/metal/rendering.rb
index b9ae8dd5ea..a3b0645dc0 100644
--- a/actionpack/lib/action_controller/metal/rendering.rb
+++ b/actionpack/lib/action_controller/metal/rendering.rb
@@ -1,3 +1,6 @@
+require 'active_support/deprecation'
+require 'active_support/core_ext/string/filters'
+
 module ActionController
   module Rendering
     extend ActiveSupport::Concern
@@ -74,6 +77,17 @@ module ActionController
     def _normalize_options(options) #:nodoc:
       _normalize_text(options)
 
+      if options[:text]
+        ActiveSupport::Deprecation.warn <<-WARNING.squish
+          `render :text` is deprecated because it does not actually render a
+          `text/plain` response. Switch to `render plain: 'plain text'` to
+          render as `text/plain`, `render html: '<strong>HTML</strong>'` to
+          render as `text/html`, or `render body: 'raw'` to match the deprecated
+          behavior and render with the default Content-Type, which is
+          `text/plain`.
+        WARNING
+      end
+
       if options[:html]
         options[:html] = ERB::Util.html_escape(options[:html])
       end