Merge pull request #12266 from Automattic/vkarpov15/fix-discriminator-subpopulate-string

fix(populate): handle specifying recursive populate as a string with discriminators

Author: vkarpov15

lib/model.js

@@ -4704,7 +4704,7 @@ function populate(model, docs, options, callback) {
  */
 
 function _execPopulateQuery(mod, match, select, assignmentOpts, callback) {
-  const subPopulate = utils.clone(mod.options.populate);
+  let subPopulate = utils.clone(mod.options.populate);
   const queryOptions = Object.assign({
     skip: mod.options.skip,
     limit: mod.options.limit,
@@ -4749,6 +4749,8 @@ function _execPopulateQuery(mod, match, select, assignmentOpts, callback) {
     if (mod.model.baseModelName != null) {
       if (Array.isArray(subPopulate)) {
         subPopulate.forEach(pop => { pop.strictPopulate = false; });
+      } else if (typeof subPopulate === 'string') {
+        subPopulate = { path: subPopulate, strictPopulate: false };
       } else {
         subPopulate.strictPopulate = false;
       }

test/model.populate.test.js

@@ -6467,7 +6467,7 @@ describe('model: populate:', function() {
             return Log.find({}).
               populate({
                 path: 'activity',
-                populate: { path: 'postedBy' }
+                populate: 'postedBy'
               }).
               sort({ seq: -1 });
           }).