Fix behavior of JSON encoding for Exception

Author: namusyaka

activesupport/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Fix behavior of JSON encoding for `Exception`.
+
+    *namusyaka*
+
 *   Make `number_to_phone` format number with regexp pattern.
 
         number_to_phone(18812345678, pattern: /(\d{3})(\d{4})(\d{4})/)

activesupport/lib/active_support/core_ext/object/json.rb

@@ -197,3 +197,9 @@ def as_json(options = nil)
     { :exitstatus => exitstatus, :pid => pid }
   end
 end
+
+class Exception
+  def as_json(options = nil)
+    to_s
+  end
+end

activesupport/test/json/encoding_test.rb

@@ -422,6 +422,11 @@ def test_twz_to_json_when_wrapping_a_date_time
     assert_equal '"1999-12-31T19:00:00.000-05:00"', ActiveSupport::JSON.encode(time)
   end
 
+  def test_exception_to_json
+    exception = Exception.new("foo")
+    assert_equal '"foo"', ActiveSupport::JSON.encode(exception)
+  end
+
   protected
 
     def object_keys(json_object)