Merge pull request #23810 from xijo/fix_json_coder_when_mysql_strict_is_disabled

Fix bug in JSON deserialization when column default is an empty string

activerecord/CHANGELOG.md

@@ -1,2 +1,6 @@
+*   Handle JSON deserialization correctly if the column default from database
+    adapter returns `''` instead of `nil`.
+
+    *Johannes Opper*
 
 Please check [5-0-stable](https://github.com/rails/rails/blob/5-0-stable/activerecord/CHANGELOG.md) for previous changes.

activerecord/lib/active_record/coders/json.rb

@@ -6,7 +6,7 @@ module ActiveRecord
       end
 
       def self.load(json)
-        ActiveSupport::JSON.decode(json) unless json.nil?
+        ActiveSupport::JSON.decode(json) unless json.blank?
       end
     end
   end

activerecord/test/cases/coders/json_test.rb

@@ -0,0 +1,15 @@
+require "cases/helper"
+
+module ActiveRecord
+  module Coders
+    class JSONTest < ActiveRecord::TestCase
+      def test_returns_nil_if_empty_string_given
+        assert_nil JSON.load("")
+      end
+
+      def test_returns_nil_if_nil_given
+        assert_nil JSON.load(nil)
+      end
+    end
+  end
+end