let's warn with heredocs

The current style for warning messages without newlines uses
concatenation of string literals with manual trailing spaces
where needed.

Heredocs have better readability, and with `squish` we can still
produce a single line.

This is a similar use case to the one that motivated defining
`strip_heredoc`, heredocs are super clean.

1 files changed, 7 insertions, 4 deletions

diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 7038f0997f..a5ee1e2159 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -1,5 +1,6 @@
 require 'active_support/core_ext/hash/indifferent_access'
 require 'active_support/core_ext/array/wrap'
+require 'active_support/core_ext/string/filters'
 require 'active_support/deprecation'
 require 'active_support/rescuable'
 require 'action_dispatch/http/upload'
@@ -114,10 +115,12 @@ module ActionController
 
     def self.const_missing(const_name)
       super unless const_name == :NEVER_UNPERMITTED_PARAMS
-      ActiveSupport::Deprecation.warn "`ActionController::Parameters::NEVER_UNPERMITTED_PARAMS`"\
-                                      " has been deprecated. Use "\
-                                      "`ActionController::Parameters.always_permitted_parameters` instead."
-      self.always_permitted_parameters
+      ActiveSupport::Deprecation.warn(<<-MSG.squish)
+        `ActionController::Parameters::NEVER_UNPERMITTED_PARAMS` has been deprecated.
+        Use `ActionController::Parameters.always_permitted_parameters` instead.
+      MSG
+
+      always_permitted_parameters
     end
 
     # Returns a new instance of <tt>ActionController::Parameters</tt>.