Support projecting fields in queries

src/parse-mockdb.js

@@ -596,12 +596,28 @@ function sortQueryresults(matches, order) {
   return _.orderBy(matches, keys, orders);
 }
 
+/**
+ * Projects out specific fields in the response (the `keys` parameter
+ * in the REST API).
+ */
+function projectFields(objects, fields) {
+  const realFields = [
+    ...fields.split(','),
+    'objectId',
+    'createdAt',
+    'updatedAt',
+    'ACL',
+  ];
+  return objects.map(object => _.pick(object, realFields));
+}
+
 /**
  * Handles a GET request (Parse.Query.find(), get(), first(), Parse.Object.fetch())
  */
 function handleGetRequest(request) {
   const objId = request.objectId;
   const className = request.className;
+  const data = request.data;
   if (objId) {
     // Object.fetch() query
     const collection = getCollection(className);
@@ -619,9 +635,12 @@ function handleGetRequest(request) {
       match = _.omit(match, toOmit);
     }
 
+    if (data.keys) {
+      match = projectFields([match], data.keys)[0];
+    }
+
     return Promise.resolve(respond(200, match));
   }
-  const data = request.data;
   indirect = data.redirectClassNameForKey;
   let matches = recursivelyMatch(className, data.where);
   let matchesClassName = '';
@@ -656,6 +675,10 @@ function handleGetRequest(request) {
     matches = sortQueryresults(matches, data.order);
   }
 
+  if (data.keys) {
+    matches = projectFields(matches, data.keys);
+  }
+
   const limit = data.limit || DEFAULT_LIMIT;
   const startIndex = data.skip || 0;
   const endIndex = startIndex + limit;

test/test.js

@@ -27,9 +27,12 @@ Parse.Object.registerSubclass('Store', Store);
 
 class CustomUserSubclass extends Parse.User { }
 
-function createBrandP(name) {
+function createBrandP(name, extra) {
   const brand = new Brand();
   brand.set('name', name);
+  if (extra) {
+    brand.set(extra);
+  }
   return brand.save();
 }
 
@@ -1553,6 +1556,65 @@ describe('ParseMock', () => {
     })
   );
 
+  describe('projecting fields', () => {
+    let savedBrand;
+    const brandExtra = { type: 'utility' };
+    beforeEach(() => createBrandP('ACME', brandExtra).then((brand) => { savedBrand = brand; }));
+
+    let savedItem;
+    const itemExtra = { name: 'Dynamite', description: 'Blows up.' };
+    beforeEach(() => createItemP(30, savedBrand, itemExtra).then((item) => { savedItem = item; }));
+
+    it('can project when fetching a single item', () => (
+      new Parse.Query(Item).select('name').get(savedItem.id).then((item) => {
+        assert(item.id); // "id" is always projected
+        assert(item.createdAt); // "createdAt" is always projected
+        assert(item.updatedAt); // "updatedAt" is always projected
+        assert.equal(item.get('price'), undefined); // this attribute was set but not projected
+        assert.equal(item.get('name'), 'Dynamite'); // this attribute was projected
+      })
+    ));
+
+    it('can project a single field passed as a string', () => (
+      new Parse.Query(Item).select('name').find().then((items) => {
+        assert.equal(items.length, 1);
+        const item = items[0];
+        assert(item.id); // "id" is always projected
+        assert(item.createdAt); // "createdAt" is always projected
+        assert(item.updatedAt); // "updatedAt" is always projected
+        assert.equal(item.get('price'), undefined); // this attribute was set but not projected
+        assert.equal(item.get('name'), 'Dynamite'); // this attribute was projected
+      })
+    ));
+
+    it('can project multiple fields passed as an array', () => (
+      new Parse.Query(Item).select(['name', 'price']).find().then((items) => {
+        assert.equal(items.length, 1);
+        const item = items[0];
+        assert(item.id); // "id" is always projected
+        assert(item.createdAt); // "createdAt" is always projected
+        assert(item.updatedAt); // "updatedAt" is always projected
+        assert.equal(item.get('price'), 30); // this attribute was projected
+        assert.equal(item.get('name'), 'Dynamite'); // this attribute was projected
+        assert.equal(item.get('description'), undefined); // this attribute was not projected
+      })
+    ));
+
+    it('can project fields from nested objects', () => {
+      new Parse.Query(Item)
+        .select(['name', 'brand.type'])
+        .find()
+        .then((items) => {
+          assert.equal(items.length, 1);
+          const item = items[0];
+          const brand = item.get('brand');
+          assert(brand);
+          assert.equal(brand.get('type'), 'utility'); // this attribute was projected
+          assert.equal(brand.get('name'), undefined); // this attribute was not projected
+        });
+    });
+  });
+
   it('should correctly handle matchesQuery', () =>
     createBrandP('Acme').then((brand) =>
       createItemP(30, brand).then((item) =>