Make OpenStruct support as optional

lib/json/add/ostruct.rb

@@ -2,7 +2,10 @@
 unless defined?(::JSON::JSON_LOADED) and ::JSON::JSON_LOADED
   require 'json'
 end
-require 'ostruct'
+begin
+  require 'ostruct'
+rescue LoadError
+end
 
 class OpenStruct
 
@@ -48,4 +51,4 @@ def as_json(*)
   def to_json(*args)
     as_json.to_json(*args)
   end
-end
+end if defined?(::OpenStruct)

lib/json/generic_object.rb

@@ -1,5 +1,8 @@
 #frozen_string_literal: false
-require 'ostruct'
+begin
+  require 'ostruct'
+rescue LoadError
+end
 
 module JSON
   class GenericObject < OpenStruct
@@ -67,5 +70,5 @@ def as_json(*)
     def to_json(*a)
       as_json.to_json(*a)
     end
-  end
+  end if defined?(::OpenStruct)
 end

tests/json_addition_test.rb

@@ -190,7 +190,7 @@ def test_ostruct
     # XXX this won't work; o.foo = { :bar => true }
     o.foo = { 'bar' => true }
     assert_equal o, parse(JSON(o), :create_additions => true)
-  end
+  end if defined?(::OpenStruct)
 
   def test_set
     s = Set.new([:a, :b, :c, :a])

tests/json_generic_object_test.rb

@@ -79,4 +79,4 @@ def switch_json_creatable
   ensure
     JSON::GenericObject.json_creatable = false
   end
-end
+end if defined?(JSON::GenericObject)

tests/json_parser_test.rb

@@ -3,7 +3,10 @@
 require_relative 'test_helper'
 require 'stringio'
 require 'tempfile'
-require 'ostruct'
+begin
+  require 'ostruct'
+rescue LoadError
+end
 begin
   require 'bigdecimal'
 rescue LoadError
@@ -412,46 +415,48 @@ def self.json_create(o)
     end
   end
 
-  class SubOpenStruct < OpenStruct
-    def [](k)
-      __send__(k)
-    end
-
-    def []=(k, v)
-      @item_set = true
-      __send__("#{k}=", v)
-    end
-
-    def item_set?
-      @item_set
-    end
-  end
-
   def test_parse_object_custom_hash_derived_class
     res = parse('{"foo":"bar"}', :object_class => SubHash)
     assert_equal({"foo" => "bar"}, res)
     assert_equal(SubHash, res.class)
     assert res.item_set?
   end
 
-  def test_parse_object_custom_non_hash_derived_class
-    res = parse('{"foo":"bar"}', :object_class => SubOpenStruct)
-    assert_equal "bar", res.foo
-    assert_equal(SubOpenStruct, res.class)
-    assert res.item_set?
-  end
+  if defined?(::OpenStruct)
+    class SubOpenStruct < OpenStruct
+      def [](k)
+        __send__(k)
+      end
 
-  def test_parse_generic_object
-    res = parse(
-      '{"foo":"bar", "baz":{}}',
-      :object_class => JSON::GenericObject
-    )
-    assert_equal(JSON::GenericObject, res.class)
-    assert_equal "bar", res.foo
-    assert_equal "bar", res["foo"]
-    assert_equal "bar", res[:foo]
-    assert_equal "bar", res.to_hash[:foo]
-    assert_equal(JSON::GenericObject, res.baz.class)
+      def []=(k, v)
+        @item_set = true
+        __send__("#{k}=", v)
+      end
+
+      def item_set?
+        @item_set
+      end
+    end
+
+    def test_parse_object_custom_non_hash_derived_class
+      res = parse('{"foo":"bar"}', :object_class => SubOpenStruct)
+      assert_equal "bar", res.foo
+      assert_equal(SubOpenStruct, res.class)
+      assert res.item_set?
+    end
+
+    def test_parse_generic_object
+      res = parse(
+        '{"foo":"bar", "baz":{}}',
+        :object_class => JSON::GenericObject
+      )
+      assert_equal(JSON::GenericObject, res.class)
+      assert_equal "bar", res.foo
+      assert_equal "bar", res["foo"]
+      assert_equal "bar", res[:foo]
+      assert_equal "bar", res.to_hash[:foo]
+      assert_equal(JSON::GenericObject, res.baz.class)
+    end
   end
 
   def test_generate_core_subclasses_with_new_to_json