Fixes #8317 map(...)

lib/types/documentarray.js

@@ -180,6 +180,11 @@ class CoreDocumentArray extends CoreMongooseArray {
     return arr;
   }
 
+  map() {
+    const arr = [].concat(Array.prototype.map.apply(this,arguments));
+    return arr;
+  }
+
   /**
    * Wraps [`Array#push`](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/push) with proper change tracking.
    *
@@ -328,18 +333,18 @@ if (util.inspect.custom) {
 
 function _updateParentPopulated(arr) {
   const parent = arr[arrayParentSymbol];
-  if (parent.$__.populated != null) {
-    const populatedPaths = Object.keys(parent.$__.populated).
-      filter(p => p.startsWith(arr[arrayPathSymbol] + '.'));
+  if (!parent || parent.$__.populated == null) return;
 
-    for (const path of populatedPaths) {
-      const remnant = path.slice((arr[arrayPathSymbol] + '.').length);
-      if (!Array.isArray(parent.$__.populated[path].value)) {
-        continue;
-      }
+  const populatedPaths = Object.keys(parent.$__.populated).
+    filter(p => p.startsWith(arr[arrayPathSymbol] + '.'));
 
-      parent.$__.populated[path].value = arr.map(val => val.populated(remnant));
+  for (const path of populatedPaths) {
+    const remnant = path.slice((arr[arrayPathSymbol] + '.').length);
+    if (!Array.isArray(parent.$__.populated[path].value)) {
+      continue;
     }
+
+    parent.$__.populated[path].value = arr.map(val => val.populated(remnant));
   }
 }
 

test/types.documentarray.test.js

@@ -575,6 +575,40 @@ describe('types.documentarray', function() {
       assert.equal(arr.length, 1);
       assert.equal(doc.docs.length, 2);
     });
+
+    it('map() works and does not return a mongoose array', function() {
+      const personSchema = new Schema({ friends: [{ name: { type: String } }]});
+      const Person = mongoose.model('gh8317-map', personSchema);
+
+      const person = new Person({ friends: [{ name: 'Hafez' }] });
+
+      const friendsNames = person.friends.map(friend => friend.name);
+      assert.deepEqual(friendsNames.constructor, Array);
+
+      friendsNames.push('Sam');
+
+      assert.equal(friendsNames.length, 2);
+      assert.equal(friendsNames[1], 'Sam');
+    });
+
+    it('filter() copies parent and path (gh-8317)', function() {
+      const personSchema = new Schema({ friends: [{ name: { type: String }, age: { type: Number } }] });
+      const Person = mongoose.model('gh8317-filter', personSchema);
+
+      const person = new Person({ friends: [
+        { name: 'Hafez', age: 25 },
+        { name: 'Sam', age: 27 }
+      ] });
+
+      const filteredFriends = person.friends.filter(friend => friend.age > 26);
+      assert.ok(filteredFriends.isMongooseArray);
+      assert.equal(filteredFriends.constructor.name, 'CoreDocumentArray');
+
+      filteredFriends.push({ name: 'John', age: 30 });
+
+      assert.equal(filteredFriends.length, 2);
+      assert.equal(filteredFriends[1].name, 'John');
+    });
   });
 
   it('cleans modified subpaths on splice() (gh-7249)', function() {