HashWithIndifferentAccess better respects #to_hash

In particular, `.new`, `#update`, `#merge`, `#replace` all accept
objects which respond to `#to_hash`, even if those objects are not
Hashes directly.

3 files changed, 51 insertions, 3 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 7feb820d4f..556e94d184 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   `HashWithIndifferentAccess` better respects `#to_hash` on objects it's
+    given. In particular, `.new`, `#update`, `#merge`, `#replace` all accept
+    objects which respond to `#to_hash`, even if those objects are not Hashes
+    directly.
+
+    *Peter Jaros*
+
 *   Deprecate `Class#superclass_delegating_accessor`, use `Class#class_attribute` instead.
 
     *Akshay Vishnoi*
diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index 594a4ca938..a4ebdea598 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -55,9 +55,9 @@ module ActiveSupport
     end
 
     def initialize(constructor = {})
-      if constructor.is_a?(Hash)
+      if constructor.respond_to?(:to_hash)
         super()
-        update(constructor)
+        update(constructor.to_hash)
       else
         super(constructor)
       end
@@ -72,6 +72,7 @@ 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
       end
@@ -125,7 +126,7 @@ 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
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index 40c8f03374..69a380c7cb 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -23,6 +23,16 @@ class HashExtTest < ActiveSupport::TestCase
     end
   end
 
+  class HashByConversion
+    def initialize(hash)
+      @hash = hash
+    end
+
+    def to_hash
+      @hash
+    end
+  end
+
   def setup
     @strings = { 'a' => 1, 'b' => 2 }
     @nested_strings = { 'a' => { 'b' => { 'c' => 3 } } }
@@ -411,6 +421,12 @@ class HashExtTest < ActiveSupport::TestCase
     assert [updated_with_strings, updated_with_symbols, updated_with_mixed].all? { |h| h.keys.size == 2 }
   end
 
+  def test_update_with_to_hash_conversion
+    hash = HashWithIndifferentAccess.new
+    hash.update HashByConversion.new({ :a => 1 })
+    assert_equal hash['a'], 1
+  end
+
   def test_indifferent_merging
     hash = HashWithIndifferentAccess.new
     hash[:a] = 'failure'
@@ -430,6 +446,12 @@ class HashExtTest < ActiveSupport::TestCase
     assert_equal 2, hash['b']
   end
 
+  def test_merge_with_to_hash_conversion
+    hash = HashWithIndifferentAccess.new
+    merged = hash.merge HashByConversion.new({ :a => 1 })
+    assert_equal merged['a'], 1
+  end
+
   def test_indifferent_replace
     hash = HashWithIndifferentAccess.new
     hash[:a] = 42
@@ -442,6 +464,18 @@ class HashExtTest < ActiveSupport::TestCase
     assert_same hash, replaced
   end
 
+  def test_replace_with_to_hash_conversion
+    hash = HashWithIndifferentAccess.new
+    hash[:a] = 42
+
+    replaced = hash.replace(HashByConversion.new(b: 12))
+
+    assert hash.key?('b')
+    assert !hash.key?(:a)
+    assert_equal 12, hash[:b]
+    assert_same hash, replaced
+  end
+
   def test_indifferent_merging_with_block
     hash = HashWithIndifferentAccess.new
     hash[:a] = 1
@@ -893,6 +927,12 @@ class HashExtTest < ActiveSupport::TestCase
     assert_equal({}, h.compact!)
     assert_equal({}, h)
   end
+
+  def test_new_with_to_hash_conversion
+    hash = HashWithIndifferentAccess.new(HashByConversion.new(a: 1))
+    assert hash.key?('a')
+    assert_equal 1, hash[:a]
+  end
 end
 
 class IWriteMyOwnXML