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, 6 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index eba51baba1..e197f7f2f9 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -2,6 +2,7 @@ require 'thread'
 require 'thread_safe'
 require 'monitor'
 require 'set'
+require 'active_support/core_ext/string/filters'
 
 module ActiveRecord
   # Raised when a connection could not be obtained within the connection
@@ -518,10 +519,11 @@ module ActiveRecord
       end
 
       def connection_pools
-        ActiveSupport::Deprecation.warn(
-          "In the next release, this will return the same as #connection_pool_list. " \
-          "(An array of pools, rather than a hash mapping specs to pools.)"
-        )
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          In the next release, this will return the same as #connection_pool_list.
+          (An array of pools, rather than a hash mapping specs to pools.)
+        MSG
+
         Hash[connection_pool_list.map { |pool| [pool.spec, pool] }]
       end