support group by

Signed-off-by: Muhammad Aaqil <aaqilcs102@gmail.com>

lib/dao.js

@@ -179,10 +179,12 @@ DataAccessObject._forDB = function(data) {
   const res = {};
   for (const propName in data) {
     const type = this.getPropertyType(propName);
-    if (type === 'JSON' || type === 'Any' || type === 'Object' || data[propName] instanceof Array) {
-      res[propName] = JSON.stringify(data[propName]);
+    const value = data[propName];
+    if (value !== null && (type === 'JSON' || type === 'Any' ||
+        type === 'Object' || value instanceof Array)) {
+      res[propName] = JSON.stringify(value);
     } else {
-      res[propName] = data[propName];
+      res[propName] = value;
     }
   }
   return res;

test/loopback-dl.test.js

@@ -1363,6 +1363,58 @@ describe('Model define with scopes configuration', function() {
   });
 });
 
+describe('DataAccessObject._forDB', function() {
+  const ds = new DataSource('memory');
+  const dao = ds.DataAccessObject;
+
+  it('should return input data if dataSource is not relational', function() {
+    const inputData = {testKey: 'testValue'};
+    dao.getDataSource = () => ({isRelational: () => false});
+
+    const outputData = dao._forDB(inputData);
+
+    assert.deepEqual(outputData, inputData);
+  });
+
+  it('should return JSON stringified values for appropriate types', function() {
+    const inputData = {
+      key1: [1, 2, 3],
+      key2: {subKey: 'value'},
+      key3: 'nonJSONvalue',
+    };
+    dao.getDataSource = () => ({isRelational: () => true});
+    dao.getPropertyType = (propName) => (propName !== 'key3' ? 'JSON' : 'String');
+
+    const outputData = dao._forDB(inputData);
+
+    assert.deepEqual(outputData, {
+      key1: JSON.stringify([1, 2, 3]),
+      key2: JSON.stringify({subKey: 'value'}),
+      key3: 'nonJSONvalue',
+    });
+  });
+
+  it('should return original value for non JSON, non Array types', function() {
+    const inputData = {key1: 'string', key2: 123, key3: true};
+    dao.getDataSource = () => ({isRelational: () => true});
+    dao.getPropertyType = () => 'String';
+
+    const outputData = dao._forDB(inputData);
+
+    assert.deepEqual(outputData, inputData);
+  });
+
+  it('should not process null values', function() {
+    const inputData = {key1: 'value', key2: null};
+    dao.getDataSource = () => ({isRelational: () => true});
+    dao.getPropertyType = (propName) => 'JSON';
+
+    const outputData = dao._forDB(inputData);
+
+    assert.deepEqual(outputData, {key1: JSON.stringify('value'), key2: null});
+  });
+});
+
 describe('DataAccessObject', function() {
   let ds, model, where, error, filter;