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.

4 files changed, 26 insertions, 15 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
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index 7534fde03e..1aed8b0457 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -60,11 +60,12 @@ module ActiveRecord
       def emit_warning_if_null_unspecified(options)
         return if options.key?(:null)
 
-        ActiveSupport::Deprecation.warn \
-          "`timestamp` was called without specifying an option for `null`. In Rails " \
-          "5.0, this behavior will change to `null: false`. You should manually " \
-          "specify `null: true` to prevent the behavior of your existing migrations " \
-          "from changing."
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          `timestamp` was called without specifying an option for `null`. In Rails
+          5.0, this behavior will change to `null: false`. You should manually
+          specify `null: true` to prevent the behavior of your existing migrations
+          from changing.
+        MSG
       end
     end
 
diff --git a/activerecord/lib/active_record/connection_adapters/connection_specification.rb b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
index e02824b33d..af405fc690 100644
--- a/activerecord/lib/active_record/connection_adapters/connection_specification.rb
+++ b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
@@ -1,4 +1,5 @@
 require 'uri'
+require 'active_support/core_ext/string/filters'
 
 module ActiveRecord
   module ConnectionAdapters
@@ -221,8 +222,12 @@ module ActiveRecord
           # this ambiguous behaviour and in the future this function
           # can be removed in favor of resolve_url_connection.
           if configurations.key?(spec) || spec !~ /:/
-            ActiveSupport::Deprecation.warn "Passing a string to ActiveRecord::Base.establish_connection " \
-              "for a configuration lookup is deprecated, please pass a symbol (#{spec.to_sym.inspect}) instead"
+            ActiveSupport::Deprecation.warn(<<-MSG.squish)
+              Passing a string to ActiveRecord::Base.establish_connection for a
+              configuration lookup is deprecated, please pass a symbol
+              (#{spec.to_sym.inspect}) instead
+            MSG
+
             resolve_symbol_connection(spec)
           else
             resolve_url_connection(spec)
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
index 84b9490ba3..961e6224c4 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
@@ -1,3 +1,5 @@
+require 'active_support/core_ext/string/filters'
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
@@ -25,10 +27,11 @@ module ActiveRecord
             if !infinity?(from) && extracted[:exclude_start]
               if from.respond_to?(:succ)
                 from = from.succ
-                ActiveSupport::Deprecation.warn \
-                  "Excluding the beginning of a Range is only partialy supported " \
-                  "through `#succ`. This is not reliable and will be removed in " \
-                  "the future."
+                ActiveSupport::Deprecation.warn(<<-MSG.squish)
+                  Excluding the beginning of a Range is only partialy supported
+                  through `#succ`. This is not reliable and will be removed in
+                  the future.
+                MSG
               else
                 raise ArgumentError, "The Ruby Range object does not support excluding the beginning of a Range. (unsupported value: '#{value}')"
               end