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

3 files changed, 20 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 0c14c0ea86..c677178253 100644
--- a/activerecord/CHANGELOG.md
+++ b/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.
diff --git a/activerecord/lib/active_record/coders/json.rb b/activerecord/lib/active_record/coders/json.rb
index 75d3bfe625..cb185a881e 100644
--- a/activerecord/lib/active_record/coders/json.rb
+++ b/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
diff --git a/activerecord/test/cases/coders/json_test.rb b/activerecord/test/cases/coders/json_test.rb
new file mode 100644
index 0000000000..d22d93d129
--- /dev/null
+++ b/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