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.

3 files changed, 28 insertions, 16 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>.
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
 
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 6acee80513..746742a85f 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -6,6 +6,7 @@ require 'active_support/core_ext/object/to_query'
 require 'active_support/core_ext/hash/slice'
 require 'active_support/core_ext/module/remove_method'
 require 'active_support/core_ext/array/extract_options'
+require 'active_support/core_ext/string/filters'
 require 'action_controller/metal/exceptions'
 require 'action_dispatch/http/request'
 require 'action_dispatch/routing/endpoint'
@@ -325,20 +326,22 @@ module ActionDispatch
       LEGACY  = ->(options) {
         if options.key?(:only_path)
           if options[:only_path]
-            ActiveSupport::Deprecation.warn \
-              "You are calling a `*_path` helper with the `only_path` option " \
-              "explicitly set to `true`. This option will stop working on " \
-              "path helpers in Rails 5. Simply remove the `only_path: true` " \
-              "argument from your call as it is redundant when applied to a " \
-              "path helper."
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
+              You are calling a `*_path` helper with the `only_path` option
+              explicitly set to `true`. This option will stop working on
+              path helpers in Rails 5. Simply remove the `only_path: true`
+              argument from your call as it is redundant when applied to a
+              path helper.
+            MSG
 
             PATH.call(options)
           else
-            ActiveSupport::Deprecation.warn \
-              "You are calling a `*_path` helper with the `only_path` option " \
-              "explicitly set to `false`. This option will stop working on " \
-              "path helpers in Rails 5. Use the corresponding `*_url` helper " \
-              "instead."
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
+              You are calling a `*_path` helper with the `only_path` option
+              explicitly set to `false`. This option will stop working on
+              path helpers in Rails 5. Use the corresponding `*_url` helper
+              instead.
+            MSG
 
             FULL.call(options)
           end