Allow select (keys) to be altered in triggers

Inspect the keys when a query is returned from a trigger and respect the new
value.

Author: Arthur Cinader

spec/CloudCode.spec.js

@@ -1306,4 +1306,41 @@ describe('beforeFind hooks', () => {
       done();
     });
   });
-})
+
+  it('should alter select', (done) => {
+    Parse.Cloud.beforeFind('MyObject', (req) => {
+      req.query.select('white');
+      return req.query;
+    });
+
+    const obj0 = new Parse.Object('MyObject')
+      .set('white', true)
+      .set('black', true)
+      .save()
+      .then(() => {
+        new Parse.Query('MyObject')
+          .first()
+          .then(result => {
+            expect(result.get('white')).toBe(true);
+            expect(result.get('black')).toBe(undefined);
+            done();
+          });
+      });
+  });
+
+  it('should not alter select', (done) => {
+    const obj0 = new Parse.Object('MyObject')
+      .set('white', true)
+      .set('black', true)
+      .save()
+      .then(() => {
+        new Parse.Query('MyObject')
+          .first()
+          .then(result => {
+            expect(result.get('white')).toBe(true);
+            expect(result.get('black')).toBe(true);
+            done();
+          });
+      });
+  });
+});

src/triggers.js

@@ -288,6 +288,10 @@ export function maybeRunQueryTrigger(triggerType, className, restWhere, restOpti
       restOptions = restOptions || {};
       restOptions.include = jsonQuery.include;
     }
+    if (jsonQuery.keys) {
+      restOptions = restOptions || {};
+      restOptions.keys = jsonQuery.keys;
+    }
     return {
       restWhere,
       restOptions