fix(QueryCursor): avoid double-applying schema paths so you can include select: false fields with + projection using cursors

Fix #13773

Author: vkarpov15

lib/cursor/QueryCursor.js

@@ -34,7 +34,7 @@ const util = require('util');
  * @api public
  */
 
-function QueryCursor(query, options) {
+function QueryCursor(query) {
   // set autoDestroy=true because on node 12 it's by default false
   // gh-10902 need autoDestroy to destroy correctly and emit 'close' event
   Readable.call(this, { autoDestroy: true, objectMode: true });
@@ -46,7 +46,7 @@ function QueryCursor(query, options) {
   this._mongooseOptions = {};
   this._transforms = [];
   this.model = model;
-  this.options = options || {};
+  this.options = {};
   model.hooks.execPre('find', query, (err) => {
     if (err != null) {
       if (err instanceof kareem.skipWrappedFunction) {
@@ -70,20 +70,18 @@ function QueryCursor(query, options) {
       this.listeners('error').length > 0 && this.emit('error', err);
       return;
     }
+    Object.assign(this.options, query._optionsForExec());
     this._transforms = this._transforms.concat(query._transforms.slice());
     if (this.options.transform) {
-      this._transforms.push(options.transform);
+      this._transforms.push(this.options.transform);
     }
     // Re: gh-8039, you need to set the `cursor.batchSize` option, top-level
     // `batchSize` option doesn't work.
     if (this.options.batchSize) {
-      this.options.cursor = options.cursor || {};
-      this.options.cursor.batchSize = options.batchSize;
-
       // Max out the number of documents we'll populate in parallel at 5000.
       this.options._populateBatchSize = Math.min(this.options.batchSize, 5000);
     }
-    Object.assign(this.options, query._optionsForExec());
+
     if (model.collection._shouldBufferCommands() && model.collection.buffer) {
       model.collection.queue.push([
         () => _getRawCursor(query, this)

lib/query.js

@@ -5043,15 +5043,13 @@ Query.prototype.cursor = function cursor(opts) {
     this.setOptions(opts);
   }
 
-  const options = this._optionsForExec();
-
   try {
     this.cast(this.model);
   } catch (err) {
-    return (new QueryCursor(this, options))._markError(err);
+    return (new QueryCursor(this))._markError(err);
   }
 
-  return new QueryCursor(this, options);
+  return new QueryCursor(this);
 };
 
 // the rest of these are basically to support older Mongoose syntax with mquery

test/query.cursor.test.js

@@ -466,11 +466,13 @@ describe('QueryCursor', function() {
     assert.equal(docs.length, 100);
   });
 
-  it('pulls schema-level readPreference (gh-8421)', function() {
+  it('pulls schema-level readPreference (gh-8421)', async function() {
     const read = 'secondaryPreferred';
     const User = db.model('User', Schema({ name: String }, { read }));
     const cursor = User.find().cursor();
 
+    await new Promise(resolve => cursor.once('cursor', resolve));
+
     assert.equal(cursor.options.readPreference, read);
   });
 
@@ -850,6 +852,32 @@ describe('QueryCursor', function() {
     assert.strictEqual(arr.length, 0);
   });
 
+  it('supports including fields using plus path that have select: false in schema (gh-13773)', async function() {
+    const kittySchema = new mongoose.Schema({
+      name: String,
+      age: {
+        select: false,
+        type: Number
+      }
+    });
+
+    db.deleteModel(/Test/);
+    const Kitten = db.model('Test', kittySchema);
+    await Kitten.deleteMany({});
+    const silence = new Kitten({ name: 'Silence', age: 2 });
+    await silence.save();
+
+    const cursor = Kitten.find().select('+age').cursor();
+
+    const kittens = [];
+    for await (const kitten of cursor) {
+      kittens.push(kitten);
+    }
+    assert.strictEqual(kittens.length, 1);
+    assert.strictEqual(kittens[0].name, 'Silence');
+    assert.strictEqual(kittens[0].age, 2);
+  });
+
   it('throws if calling skipMiddlewareFunction() with non-empty array (gh-13411)', async function() {
     const schema = new mongoose.Schema({ name: String });