Check for existence of #to_json method before call

Author: flori

lib/json/pure/generator.rb

@@ -363,7 +363,11 @@ def json_transform(state)
               result << state.space_before
               result << ':'
               result << state.space
-              result << value.to_json(state)
+              if value.respond_to?(:to_json)
+                result << value.to_json(state)
+              else
+                result << %{"#{String(value)}"}
+              end
               first = false
             }
             depth = state.depth -= 1
@@ -398,7 +402,11 @@ def json_transform(state)
             each { |value|
               result << delim unless first
               result << state.indent * depth if indent
-              result << value.to_json(state)
+              if value.respond_to?(:to_json)
+                result << value.to_json(state)
+              else
+                result << %{"#{String(value)}"}
+              end
               first = false
             }
             depth = state.depth -= 1

tests/test_json_generate.rb

@@ -342,7 +342,7 @@ def to_s; self; end
       undef to_json
     end
     assert_nothing_raised(SystemStackError) do
-      assert_equal '[""]', JSON.generate([s.new])
+      assert_equal '["foo"]', JSON.generate([s.new('foo')])
     end
   end
 end