fix(populate): make getSchemaTypes() handle embedded discriminators without a ref

Re: #5970

Author: vkarpov15

lib/services/populate/getSchemaTypes.js

@@ -8,7 +8,9 @@ var Mixed = require('../../schema/mixed');
 var mpath = require('mpath');
 
 /*!
- * ignore
+ * @param {Schema} schema
+ * @param {Object} doc POJO
+ * @param {string} path
  */
 
 module.exports = function getSchemaTypes(schema, doc, path) {
@@ -73,14 +75,14 @@ module.exports = function getSchemaTypes(schema, doc, path) {
               ret = [];
               for (var i = 0; i < schemas.length; ++i) {
                 var _ret = search(parts.slice(p), schemas[i]);
-                if (_ret) {
+                if (_ret != null) {
                   _ret.$isUnderneathDocArray = _ret.$isUnderneathDocArray ||
                     !foundschema.schema.$isSingleNested;
                   if (_ret.$isUnderneathDocArray) {
                     ret.$isUnderneathDocArray = true;
                   }
+                  ret.push(_ret);
                 }
-                ret.push(_ret);
               }
               return ret;
             } else {

test/helpers/populate.getSchemaTypes.test.js

@@ -0,0 +1,61 @@
+'use strict';
+
+var Schema = require('../../lib/schema');
+var assert = require('assert');
+var getSchemaTypes = require('../../lib/services/populate/getSchemaTypes');
+
+describe('getSchemaTypes', function() {
+  it('handles embedded discriminators (gh-5970)', function(done) {
+    var ItemSchema = new Schema({
+      title: {
+        type: String,
+        required: true
+      }
+    }, {discriminatorKey: 'type'});
+
+    var ItemBookSchema = new Schema({
+      author: {
+        type: String,
+        ref: 'Ref1'
+      }
+    });
+
+    var ItemEBookSchema = new Schema({
+      author: {
+        type: String,
+        ref: 'Ref2'
+      }
+    });
+
+    var OtherItem = new Schema({ name: String });
+
+    var BundleSchema = new Schema({
+      items: [{
+        type: ItemSchema,
+        required: false
+      }]
+    });
+
+    BundleSchema.path('items').discriminator('Book', ItemBookSchema);
+    BundleSchema.path('items').discriminator('EBook', ItemEBookSchema);
+    BundleSchema.path('items').discriminator('Other', OtherItem);
+
+    var doc = {
+      items: [
+        { type: 'Book', author: 'test 1' },
+        { type: 'EBook', author: 'test 2' },
+        { type: 'Other' },
+      ]
+    }
+    var schemaTypes = getSchemaTypes(BundleSchema, doc, 'items.author');
+
+    assert.ok(Array.isArray(schemaTypes));
+    // Make sure we only got the schema paths for Book and EBook, and none
+    // for the 'Other'
+    assert.equal(schemaTypes.length, 2);
+    assert.equal(schemaTypes[0].options.ref, 'Ref1');
+    assert.equal(schemaTypes[1].options.ref, 'Ref2');
+
+    done();
+  });
+});