Allow opting out of applying key format to values

Since rails#486, key format is also applied to nested hashes that are
passed as values:

     json.key_format! camelize: :lower
     json.settings({some_value: "abc"})

     # => { "settings": { "someValue": "abc" }}

This breaks code that relied on the previous behavior. Add a
`deep_format_keys!` directive that can be used to opt out of the new
behavior.

Author: tf

README.md

@@ -274,6 +274,33 @@ environment.rb for example):
 Jbuilder.key_format camelize: :lower
 ```
 
+Since version 2.11, key format is also applied to nested hashes that
+are passed as values:
+
+``` ruby
+json.key_format! camelize: :lower
+json.settings({some_value: "abc"})
+
+# => { "settings": { "someValue": "abc" }}
+```
+
+If you'd like to preserve the previous behavior, you can opt out:
+
+``` ruby
+json.key_format! camelize: :lower
+json.deep_format_keys! false
+json.settings({some_value: "abc"})
+
+# => { "settings": { "some_value": "abc" }}
+```
+
+You can set this globally with the class method `deep_format_keys` (from inside your
+environment.rb for example):
+
+``` ruby
+Jbuilder.deep_format_keys false
+```
+
 ## Contributing to Jbuilder
 
 Jbuilder is the work of many contributors. You're encouraged to submit pull requests, propose

lib/jbuilder.rb

@@ -9,12 +9,14 @@
 class Jbuilder
   @@key_formatter = nil
   @@ignore_nil    = false
+  @@deep_format_keys = true
 
   def initialize(options = {})
     @attributes = {}
 
     @key_formatter = options.fetch(:key_formatter){ @@key_formatter ? @@key_formatter.clone : nil}
     @ignore_nil = options.fetch(:ignore_nil, @@ignore_nil)
+    @deep_format_keys = options.fetch(:deep_format_keys, @@deep_format_keys)
 
     yield self if ::Kernel.block_given?
   end
@@ -131,6 +133,32 @@ def self.ignore_nil(value = true)
     @@ignore_nil = value
   end
 
+  # Since version 2.11 key format is also applied to nested hashes and
+  # arrays passed to methods like set!, merge! or array!. You can opt
+  # out of this behavior.
+  #
+  # Example:
+  #
+  #   json.key_format! camelize: :lower
+  #   json.settings({some_value: "abc"})
+  #
+  #   { "settings": { "someValue": "abc" }}
+  #
+  #   json.key_format! camelize: :lower
+  #   json.deep_format_keys! false
+  #   json.settings({some_value: "abc"})
+  #
+  #   { "settings": { "some_value": "abc" }}
+  #
+  def deep_format_keys!(value)
+    @deep_format_keys = value
+  end
+
+  # Same as instance method deep_format_keys! except sets the default.
+  def self.deep_format_keys(value)
+    @@deep_format_keys = value
+  end
+
   # Turns the current element into an array and yields a builder to add a hash.
   #
   # Example:
@@ -288,6 +316,8 @@ def _key(key)
   end
 
   def _format_keys(hash_or_array)
+    return hash_or_array unless @deep_format_keys
+
     if ::Array === hash_or_array
       hash_or_array.map { |value| _format_keys(value) }
     elsif ::Hash === hash_or_array
@@ -312,12 +342,12 @@ def _map_collection(collection)
   end
 
   def _scope
-    parent_attributes, parent_formatter = @attributes, @key_formatter
+    parent_attributes, parent_formatter, parent_deep_format_keys = @attributes, @key_formatter, @deep_format_keys
     @attributes = BLANK
     yield
     @attributes
   ensure
-    @attributes, @key_formatter = parent_attributes, parent_formatter
+    @attributes, @key_formatter, @deep_format_keys = parent_attributes, parent_formatter, parent_deep_format_keys
   end
 
   def _is_collection?(object)

test/jbuilder_test.rb

@@ -729,6 +729,45 @@ class JbuilderTest < ActiveSupport::TestCase
     assert_empty cache
   end
 
+  test 'applying key_format! deeply can be disabled' do
+    names = { first_name: 'camel', last_name: 'case' }
+    result = jbuild do |json|
+      json.key_format! camelize: :lower
+      json.deep_format_keys! false
+      json.set! :all_names, names
+    end
+
+    assert_equal %i[first_name last_name], result['allNames'].keys
+  end
+
+  test 'applying key_format! deeply can be disabled per scope' do
+    names = { first_name: 'camel', last_name: 'case' }
+    result = jbuild do |json|
+      json.key_format! camelize: :lower
+      json.scope do
+        json.deep_format_keys! false
+        json.set! :all_names, names
+      end
+      json.set! :all_names, names
+    end
+
+    assert_equal %i[first_name last_name], result['scope']['allNames'].keys
+    assert_equal %w[firstName lastName], result['allNames'].keys
+  end
+
+  test 'applying key_format! deeply can be disabled globally' do
+    names = { first_name: 'camel', last_name: 'case' }
+
+    Jbuilder.deep_format_keys false
+    result = jbuild do |json|
+      json.key_format! camelize: :lower
+      json.set! :all_names, names
+    end
+
+    assert_equal %i[first_name last_name], result['allNames'].keys
+    Jbuilder.send(:class_variable_set, '@@deep_format_keys', true)
+  end
+
   test 'ignore_nil! without a parameter' do
     result = jbuild do |json|
       json.ignore_nil!