Fix the `config_for` to always return a NonSymbolAccessDeprecatedHash:

- If you have hashes inside array, the hashes were getting initialized
  as regular HWIA wereas we want them to be
  NonSymbolAccessDeprecatedHash in order to trigger a deprecation
  warning when keys are accessed with string.

  This patch fixes that by overwriting the `[]=` to to the same
  as what HWIA does (with the difference that we don't call
  `convert_key` to not trigger a deprecation when setting value).

  I also took the liberty to extract `hash.nested_under_indifferent_access`,
  into a separate method to allow subclasses to return whatever
  they want.
  Inheriting HWIA is not common, but I think it's useful for cases
  like this one where we want to preprocess reading and writing values
  in the hash (for deprecation purposes or other reasons).

1 files changed, 18 insertions, 4 deletions

diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index d0417f8a49..fbad3e5db3 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -602,10 +602,7 @@ module Rails
         end
 
         def []=(key, value)
-          if value.is_a?(Hash)
-            value = self.class.new(value)
-          end
-          super(key.to_sym, value)
+          regular_writer(key.to_sym, convert_value(value, for: :assignment))
         end
 
         private
@@ -623,6 +620,23 @@ module Rails
 
             key
           end
+
+          def convert_value(value, options = {}) # :doc:
+            if value.is_a? Hash
+              if options[:for] == :to_hash
+                value.to_hash
+              else
+                self.class.new(value)
+              end
+            elsif value.is_a?(Array)
+              if options[:for] != :assignment || value.frozen?
+                value = value.dup
+              end
+              value.map! { |e| convert_value(e, options) }
+            else
+              value
+            end
+          end
       end
   end
 end