fix(populate): handle deselecting _id with array of fields in `popu…

…late()`

Fix #14231

lib/model.js

@@ -4298,6 +4298,8 @@ function populate(model, docs, options, callback) {
       // _id back off before returning the result.
       if (typeof select === 'string') {
         select = select.replace(excludeIdRegGlobal, ' ');
+      } else if (Array.isArray(select)) {
+        select = select.filter(field => field !== '-_id');
       } else {
         // preserve original select conditions by copying
         select = { ...select };

test/model.populate.test.js

@@ -2197,7 +2197,7 @@ describe('model: populate:', function() {
     });
 
     describe('in a subdocument', function() {
-      it('works', async function() {
+      it('works (gh-14231)', async function() {
         const docs = await U.find({ name: 'u1' }).populate('comments', { _id: 0 });
 
         let doc = docs[0];
@@ -2229,6 +2229,15 @@ describe('model: populate:', function() {
           assert.equal(typeof d._doc.__v, 'number');
         });
 
+        doc = await U.findOne({ name: 'u1' }).populate('comments', ['-_id']);
+        assert.equal(doc.comments.length, 2);
+        doc.comments.forEach(function(d) {
+          assert.equal(d._id, undefined);
+          assert.equal(Object.keys(d._doc).indexOf('_id'), -1);
+          assert.ok(d.title.length);
+          assert.ok(d.body.length);
+          assert.equal(typeof d._doc.__v, 'number');
+        });
       });
 
       it('with lean', async function() {