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, 1 deletions

diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index 99d46af953..2918a98796 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -1,4 +1,5 @@
 require 'active_support/core_ext/module/attribute_accessors'
+require 'active_support/core_ext/string/filters'
 require 'active_support/deprecation'
 require 'action_dispatch/http/filter_redirect'
 require 'monitor'
@@ -288,7 +289,12 @@ module ActionDispatch # :nodoc:
     # as arrays work, and "flattening" responses, cascading to the rack body!
     # Not sensible behavior.
     def to_ary
-      ActiveSupport::Deprecation.warn 'ActionDispatch::Response#to_ary no longer performs implicit conversion to an Array. Please use response.to_a instead, or a splat like `status, headers, body = *response`'
+      ActiveSupport::Deprecation.warn(<<-MSG.squish)
+        'ActionDispatch::Response#to_ary no longer performs implicit conversion
+        to an Array. Please use response.to_a instead, or a splat like `status,
+        headers, body = *response`
+      MSG
+
       to_a
     end