Properly serialize all JSON primitives in the AR JSON type

Previously we were assuming that the only valid types for encoding were
arrays and hashes. However, any JSON primitive is an accepted value by
both PG and MySQL.

This does involve a minor breaking change in the handling of `default`
in the schema dumper. This is easily worked around, as passing a
hash/array literal would have worked fine in previous versions of Rails.
However, because of this, I will not be backporting this to 4.2 or
earlier.

Fixes #24234

activerecord/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Properly accept all valid JSON primitives in the JSON data type.
+
+    Fixes #24234
+
+    *Sean Griffin*
+
 *   MariaDB 5.3+ supports microsecond datetime precision.
 
     *Jeremy Daer*

activerecord/lib/active_record/type/internal/abstract_json.rb

@@ -17,11 +17,7 @@ module ActiveRecord
         end
 
         def serialize(value)
-          if value.is_a?(::Array) || value.is_a?(::Hash)
-            ::ActiveSupport::JSON.encode(value)
-          else
-            value
-          end
+          ::ActiveSupport::JSON.encode(value)
         end
 
         def accessor

activerecord/test/cases/adapters/mysql2/json_test.rb

@@ -161,12 +161,19 @@ class Mysql2JSONTest < ActiveRecord::Mysql2TestCase
     assert_not json.changed?
   end
 
-  def test_assigning_invalid_json
-    json = JsonDataType.new
+  def test_assigning_string_literal
+    json = JsonDataType.create(payload: "foo")
+    assert_equal "foo", json.payload
+  end
 
-    json.payload = 'foo'
+  def test_assigning_number
+    json = JsonDataType.create(payload: 1.234)
+    assert_equal 1.234, json.payload
+  end
 
-    assert_nil json.payload
+  def test_assigning_boolean
+    json = JsonDataType.create(payload: true)
+    assert_equal true, json.payload
   end
 end
 end

activerecord/test/cases/adapters/postgresql/json_test.rb

@@ -38,7 +38,7 @@ module PostgresqlJSONSharedTestCases
   end
 
   def test_default
-    @connection.add_column 'json_data_type', 'permissions', column_type, default: '{"users": "read", "posts": ["read", "write"]}'
+    @connection.add_column 'json_data_type', 'permissions', column_type, default: {"users": "read", "posts": ["read", "write"]}
     JsonDataType.reset_column_information
 
     assert_equal({"users"=>"read", "posts"=>["read", "write"]}, JsonDataType.column_defaults['permissions'])
@@ -178,12 +178,19 @@ module PostgresqlJSONSharedTestCases
     assert_not json.changed?
   end
 
-  def test_assigning_invalid_json
-    json = JsonDataType.new
+  def test_assigning_string_literal
+    json = JsonDataType.create(payload: "foo")
+    assert_equal "foo", json.payload
+  end
 
-    json.payload = 'foo'
+  def test_assigning_number
+    json = JsonDataType.create(payload: 1.234)
+    assert_equal 1.234, json.payload
+  end
 
-    assert_nil json.payload
+  def test_assigning_boolean
+    json = JsonDataType.create(payload: true)
+    assert_equal true, json.payload
   end
 end