Fixed Object#as_json and Struct#as_json with options

These methods now takes the same options as Hash#as_json, for example:

    struct = Struct.new(:foo, :bar).new
    struct.foo = "hello"
    struct.bar = "world"
    json = struct.as_json(only: [:foo]) # => {foo: "hello"}

This is extracted from PR #11728 from @sergiocampama, see also the
discussion in #11460.

3 files changed, 40 insertions, 5 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index e718e79877..5d39fa39d9 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,13 @@
+*   Fixed Object#as_json and Struct#as_json not working properly with options. They now take
+    the same options as Hash#as_json:
+
+        struct = Struct.new(:foo, :bar).new
+        struct.foo = "hello"
+        struct.bar = "world"
+        json = struct.as_json(only: [:foo]) # => {foo: "hello"}
+
+    *Sergio Campamá*, *Godfrey Chan*
+
 *   Added Numeric#in_milliseconds, like 1.hour.in_milliseconds, so we can feed them to JavaScript functions like getTime().
 
 	*DHH*
diff --git a/activesupport/lib/active_support/core_ext/object/json.rb b/activesupport/lib/active_support/core_ext/object/json.rb
index 554da1a2aa..c50cd57c2c 100644
--- a/activesupport/lib/active_support/core_ext/object/json.rb
+++ b/activesupport/lib/active_support/core_ext/object/json.rb
@@ -20,16 +20,16 @@ end
 class Object
   def as_json(options = nil) #:nodoc:
     if respond_to?(:to_hash)
-      to_hash
+      to_hash.as_json(options)
     else
-      instance_values
+      instance_values.as_json(options)
     end
   end
 end
 
 class Struct #:nodoc:
   def as_json(options = nil)
-    Hash[members.zip(values)]
+    Hash[members.zip(values)].as_json(options)
   end
 end
 
diff --git a/activesupport/test/json/encoding_test.rb b/activesupport/test/json/encoding_test.rb
index d549113ff4..ae8b8052ca 100644
--- a/activesupport/test/json/encoding_test.rb
+++ b/activesupport/test/json/encoding_test.rb
@@ -13,7 +13,7 @@ class TestJSONEncoding < ActiveSupport::TestCase
 
   class Hashlike
     def to_hash
-      { :a => 1 }
+      { :foo => "hello", :bar => "world" }
     end
   end
 
@@ -61,7 +61,7 @@ class TestJSONEncoding < ActiveSupport::TestCase
                    [ :"a b", %("a b")  ]]
 
   ObjectTests   = [[ Foo.new(1, 2), %({\"a\":1,\"b\":2}) ]]
-  HashlikeTests = [[ Hashlike.new, %({\"a\":1}) ]]
+  HashlikeTests = [[ Hashlike.new, %({\"bar\":\"world\",\"foo\":\"hello\"}) ]]
   CustomTests   = [[ Custom.new, '"custom"' ]]
 
   RegexpTests   = [[ /^a/, '"(?-mix:^a)"' ], [/^\w{1,2}[a-z]+/ix, '"(?ix-m:^\\\\w{1,2}[a-z]+)"']]
@@ -204,6 +204,31 @@ class TestJSONEncoding < ActiveSupport::TestCase
     end
   end
 
+  def test_hash_like_with_options
+    h = Hashlike.new
+    json = h.to_json :only => [:foo]
+
+    assert_equal({"foo"=>"hello"}, JSON.parse(json))
+  end
+
+  def test_object_to_json_with_options
+    obj = Object.new
+    obj.instance_variable_set :@foo, "hello"
+    obj.instance_variable_set :@bar, "world"
+    json = obj.to_json :only => ["foo"]
+
+    assert_equal({"foo"=>"hello"}, JSON.parse(json))
+  end
+
+  def test_struct_to_json_with_options
+    struct = Struct.new(:foo, :bar).new
+    struct.foo = "hello"
+    struct.bar = "world"
+    json = struct.to_json :only => [:foo]
+
+    assert_equal({"foo"=>"hello"}, JSON.parse(json))
+  end
+
   def test_hash_should_pass_encoding_options_to_children_in_as_json
     person = {
       :name => 'John',