1 files changed, 26 insertions, 12 deletions

diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index 3da99872c0..c7477b9ff4 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -1,4 +1,5 @@
 require 'active_support/core_ext/hash/keys'
+require 'active_support/core_ext/hash/reverse_merge'
 
 module ActiveSupport
   # Implements a hash where keys <tt>:foo</tt> and <tt>"foo"</tt> are considered
@@ -55,7 +56,7 @@ module ActiveSupport
     end
 
     def initialize(constructor = {})
-      if constructor.is_a?(Hash)
+      if constructor.respond_to?(:to_hash)
         super()
         update(constructor)
       else
@@ -72,8 +73,10 @@ module ActiveSupport
     end
 
     def self.new_from_hash_copying_default(hash)
+      hash = hash.to_hash
       new(hash).tap do |new_hash|
         new_hash.default = hash.default
+        new_hash.default_proc = hash.default_proc if hash.default_proc
       end
     end
 
@@ -125,7 +128,7 @@ module ActiveSupport
       if other_hash.is_a? HashWithIndifferentAccess
         super(other_hash)
       else
-        other_hash.each_pair do |key, value|
+        other_hash.to_hash.each_pair do |key, value|
           if block_given? && key?(key)
             value = yield(convert_key(key), self[key], value)
           end
@@ -159,7 +162,7 @@ module ActiveSupport
     #
     #   counters.fetch('foo')          # => 1
     #   counters.fetch(:bar, 0)        # => 0
-    #   counters.fetch(:bar) {|key| 0} # => 0
+    #   counters.fetch(:bar) { |key| 0 } # => 0
     #   counters.fetch(:zoo)           # => KeyError: key not found: "zoo"
     def fetch(key, *extras)
       super(convert_key(key), *extras)
@@ -172,10 +175,17 @@ module ActiveSupport
     #   hash[:b] = 'y'
     #   hash.values_at('a', 'b') # => ["x", "y"]
     def values_at(*indices)
-      indices.collect {|key| self[convert_key(key)]}
+      indices.collect { |key| self[convert_key(key)] }
     end
 
-    # Returns an exact copy of the hash.
+    # Returns a shallow copy of the hash.
+    #
+    #   hash = ActiveSupport::HashWithIndifferentAccess.new({ a: { b: 'b' } })
+    #   dup  = hash.dup
+    #   dup[:a][:c] = 'c'
+    #
+    #   hash[:a][:c] # => nil
+    #   dup[:a][:c]  # => "c"
     def dup
       self.class.new(self).tap do |new_hash|
         new_hash.default = default
@@ -207,7 +217,7 @@ module ActiveSupport
     # Replaces the contents of this hash with other_hash.
     #
     #   h = { "a" => 100, "b" => 200 }
-    #   h.replace({ "c" => 300, "d" => 400 }) #=> {"c"=>300, "d"=>400}
+    #   h.replace({ "c" => 300, "d" => 400 }) # => {"c"=>300, "d"=>400}
     def replace(other_hash)
       super(self.class.new_from_hash_copying_default(other_hash))
     end
@@ -227,17 +237,21 @@ module ActiveSupport
     def deep_symbolize_keys; to_hash.deep_symbolize_keys! end
     def to_options!; self end
 
-    def select(*args, &block)
-      dup.tap {|hash| hash.select!(*args, &block)}
+    def select(*)
+      super.with_indifferent_access
+    end
+
+    def reject(*)
+      super.with_indifferent_access
     end
 
     # Convert to a regular hash with string keys.
     def to_hash
-      _new_hash= {}
+      _new_hash = Hash.new(default)
       each do |key, value|
-        _new_hash[convert_key(key)] = convert_value(value, for: :to_hash)
+        _new_hash[key] = convert_value(value, for: :to_hash)
       end
-      Hash.new(default).merge!(_new_hash)
+      _new_hash
     end
 
     protected
@@ -253,7 +267,7 @@ module ActiveSupport
             value.nested_under_indifferent_access
           end
         elsif value.is_a?(Array)
-          unless options[:for] == :assignment
+          if options[:for] != :assignment || value.frozen?
             value = value.dup
           end
           value.map! { |e| convert_value(e, options) }