1 files changed, 12 insertions, 8 deletions
diff --git a/activesupport/lib/active_support/core_ext/hash/keys.rb b/activesupport/lib/active_support/core_ext/hash/keys.rb
index 5934c578ea..9297a59c46 100644
--- a/activesupport/lib/active_support/core_ext/hash/keys.rb
+++ b/activesupport/lib/active_support/core_ext/hash/keys.rb
@@ -6,7 +6,8 @@ class Hash
   #  hash.transform_keys{ |key| key.to_s.upcase }
   #  # => {"NAME"=>"Rob", "AGE"=>"28"}
   def transform_keys
-    result = {}
+    return enum_for(:transform_keys) unless block_given?
+    result = self.class.new
     each_key do |key|
       result[yield(key)] = self[key]
     end
@@ -16,6 +17,7 @@ class Hash
   # Destructively convert all keys using the block operations.
   # Same as transform_keys but modifies +self+.
   def transform_keys!
+    return enum_for(:transform_keys!) unless block_given?
     keys.each do |key|
       self[yield(key)] = delete(key)
     end
@@ -29,13 +31,13 @@ class Hash
   #   hash.stringify_keys
   #   # => {"name"=>"Rob", "age"=>"28"}
   def stringify_keys
-    transform_keys{ |key| key.to_s }
+    transform_keys(&:to_s)
   end
 
   # Destructively convert all keys to strings. Same as
   # +stringify_keys+, but modifies +self+.
   def stringify_keys!
-    transform_keys!{ |key| key.to_s }
+    transform_keys!(&:to_s)
   end
 
   # Returns a new hash with all keys converted to symbols, as long as
@@ -57,9 +59,11 @@ class Hash
   end
   alias_method :to_options!, :symbolize_keys!
 
-  # Validate all keys in a hash match <tt>*valid_keys</tt>, raising ArgumentError
-  # on a mismatch. Note that keys are NOT treated indifferently, meaning if you
-  # use strings for keys but assert symbols as keys, this will fail.
+  # Validate all keys in a hash match <tt>*valid_keys</tt>, raising
+  # ArgumentError on a mismatch.
+  #
+  # Note that keys are treated differently than HashWithIndifferentAccess,
+  # meaning that string and symbol keys will not match.
   #
   #   { name: 'Rob', years: '28' }.assert_valid_keys(:name, :age) # => raises "ArgumentError: Unknown key: :years. Valid keys are: :name, :age"
   #   { name: 'Rob', age: '28' }.assert_valid_keys('name', 'age') # => raises "ArgumentError: Unknown key: :name. Valid keys are: 'name', 'age'"
@@ -101,14 +105,14 @@ class Hash
   #   hash.deep_stringify_keys
   #   # => {"person"=>{"name"=>"Rob", "age"=>"28"}}
   def deep_stringify_keys
-    deep_transform_keys{ |key| key.to_s }
+    deep_transform_keys(&:to_s)
   end
 
   # Destructively convert all keys to strings.
   # This includes the keys from the root hash and from all
   # nested hashes and arrays.
   def deep_stringify_keys!
-    deep_transform_keys!{ |key| key.to_s }
+    deep_transform_keys!(&:to_s)
   end
 
   # Returns a new hash with all keys converted to symbols, as long as