Honour allowExtendedOperators in "DAO.find"

Modify the coercion of filter.where to hounour "allowExtendedOperators"
and don't coerce property values of type object (extended operators).

lib/dao.js

@@ -1658,13 +1658,19 @@ DataAccessObject._coerce = function(where) {
       }
     } else {
       if (val != null) {
+        const dsSettings = this.getDataSource().settings;
+        const allowExtendedOperators = dsSettings.allowExtendedOperators;
         if (operator === null && val instanceof RegExp) {
           // Normalize {name: /A/} to {name: {regexp: /A/}}
           operator = 'regexp';
         } else if (operator === 'regexp' && val instanceof RegExp) {
           // Do not coerce regex literals/objects
-        } else if (!((operator === 'like' || operator === 'nlike' ||
-            operator === 'ilike' || operator === 'nilike') && val instanceof RegExp)) {
+        } else if ((operator === 'like' || operator === 'nlike' ||
+            operator === 'ilike' || operator === 'nilike') && val instanceof RegExp) {
+          // Do not coerce RegExp operator value
+        } else if (allowExtendedOperators && typeof val === 'object') {
+          // Do not coerce object values when extended operators are allowed
+        } else {
           val = DataType(val);
         }
       }

test/allow-extended-operators.test.js

@@ -0,0 +1,62 @@
+// Copyright IBM Corp. 2015,2016. All Rights Reserved.
+// Node module: loopback-datasource-juggler
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+const DataSource = require('..').DataSource;
+const should = require('should');
+
+describe('Model.settings.allowExtendedOperators', () => {
+  context('DAO.find()', () => {
+    it('converts extended operators to string value by default', () => {
+      const TestModel = createTestModel();
+      return TestModel.find(extendedQuery()).then((results) => {
+        should(results[0].value).eql('[object Object]');
+      });
+    });
+
+    it('preserves extended operators wit allowExtendedOperators set', () => {
+      const TestModel = createTestModel({allowExtendedOperators: true});
+      return TestModel.find(extendedQuery()).then((results) => {
+        should(results[0].value).eql({$exists: true});
+      });
+    });
+
+    function extendedQuery() {
+      // datasource modifies the query,
+      // we have to build a new object for each test
+      return {where: {value: {$exists: true}}};
+    }
+  });
+
+  function createTestModel(connectorSettings) {
+    const ds = createTestDataSource(connectorSettings);
+    return ds.createModel('TestModel', {value: String});
+  }
+
+  function createTestDataSource(connectorSettings) {
+    connectorSettings = connectorSettings || {};
+    connectorSettings.connector = {
+      initialize: (dataSource, cb) => {
+        dataSource.connector = new TestConnector(dataSource);
+      },
+    };
+
+    return new DataSource(connectorSettings);
+  }
+
+  class TestConnector {
+    constructor(dataSource) {
+    }
+
+    all(model, filter, options, callback) {
+      // return the raw "value" query
+      var instanceFound = {
+        value: filter.where.value,
+      };
+      callback(null, [instanceFound]);
+    }
+  }
+});