Support for plain strings, ints and bools in JSON

changelog.md

 # Next
+- [BUG] Support for plain strings, ints and bools on JSON insert
 - [BUG] Fixed regression where `{$in: []}` would result in `IN ()` rather than `IN (NULL)` [#3105](https://github.com/sequelize/sequelize/issues/3105) [#3132](https://github.com/sequelize/sequelize/issues/3132)
 - [BUG] Fixed bug where 2 x `belongsToMany` with `foreignKey` but no `otherKey` defined would result in 3 keys instead of 2. [#2991](https://github.com/sequelize/sequelize/issues/2991)
 

lib/dialects/postgres/query-generator.js

@@ -871,7 +871,7 @@ module.exports = (function() {
         } else if (DataTypes.ARRAY.is(field.type, DataTypes.HSTORE)) {
           return "ARRAY[" + Utils._.map(value, function(v){return "'" + hstore.stringify(v) + "'::hstore";}).join(",") + "]::HSTORE[]";
         }
-      } else if (Utils._.isObject(value) && field && (field.type instanceof DataTypes.JSON || field.type instanceof DataTypes.JSONB)) {
+      } else if (field && (field.type instanceof DataTypes.JSON || field.type instanceof DataTypes.JSONB)) {
         value = JSON.stringify(value);
       } else if (Array.isArray(value) && field && DataTypes.ARRAY.is(field.type, DataTypes.JSON)) {
         return "ARRAY[" + value.map(function (v) {

test/unit/sql/json.test.js

+'use strict';
+
+var Support   = require(__dirname + '/../support')
+  , DataTypes = require(__dirname + '/../../../lib/data-types')
+  , util      = require('util')
+  , expectsql = Support.expectsql
+  , current   = Support.sequelize
+  , sql       = current.dialect.QueryGenerator;
+
+// Notice: [] will be replaced by dialect specific tick/quote character when there is not dialect specific expectation but only a default expectation
+
+if (Support.getTestDialect() === 'postgres') {
+  suite(Support.getTestDialectTeaser('SQL'), function() {
+    suite('JSON', function () {
+      suite('escape', function () {
+        test('plain string', function () {
+          expectsql(sql.escape('string', { type: DataTypes.JSON}), {
+            default: '\'"string"\''
+          });
+        });
+
+        test('plain int', function () {
+          expectsql(sql.escape(123, { type: DataTypes.JSON}), {
+            default: "'123'"
+          });
+        });
+
+        test('nested object', function () {
+          expectsql(sql.escape({ some: 'nested', more: { nested: true }, answer: 42 }, { type: DataTypes.JSON}), {
+            default: "'{\"some\":\"nested\",\"more\":{\"nested\":true},\"answer\":42}'"
+          });
+        });
+
+        test('array of JSON', function () {
+          expectsql(sql.escape([
+            { some: 'nested', more: { nested: true }, answer: 42 },
+            43,
+            'joe'
+          ], { type: DataTypes.ARRAY(DataTypes.JSON)}), {
+            postgres: 'ARRAY[\'{"some":"nested","more":{"nested":true},"answer":42}\',\'43\',\'"joe"\']::JSON[]'
+          });
+        });
+      });
+    });
+  });
+}