fix(document): apply virtuals to subdocuments if parent schema has virtuals: true for backwards compatibility

lib/document.js

@@ -3801,7 +3801,7 @@ Document.prototype.$__handleReject = function handleReject(err) {
 };
 
 /**
- * Internal helper for toObject() and toJSON() that doesn't manipulate options
+ * Internal common logic for toObject() and toJSON()
  *
  * @return {Object}
  * @api private
@@ -3834,14 +3834,17 @@ Document.prototype.$toObject = function(options, json) {
   }
 
   const depopulate = options._calledWithOptions.depopulate
-    ?? options._parentOptions?.depopulate
     ?? defaultOptions?.depopulate
+    ?? options.depopulate
     ?? false;
   // _isNested will only be true if this is not the top level document, we
   // should never depopulate the top-level document
   if (depopulate && options._isNested && this.$__.wasPopulated) {
     return clone(this.$__.wasPopulated.value || this._doc._id, options);
   }
+  if (depopulate) {
+    options.depopulate = true;
+  }
 
   // merge default options with input options.
   if (defaultOptions != null) {
@@ -3855,7 +3858,9 @@ Document.prototype.$toObject = function(options, json) {
   options.json = json;
   options.minimize = _minimize;
 
-  options._parentOptions = options;
+  const parentOptions = options._parentOptions;
+  // Parent options should only bubble down for subdocuments, not populated docs
+  options._parentOptions = this.$isSubdocument ? options : null;
 
   options._skipSingleNestedGetters = false;
   // remember the root transform function
@@ -3886,6 +3891,7 @@ Document.prototype.$toObject = function(options, json) {
 
   const virtuals = options._calledWithOptions.virtuals
     ?? defaultOptions.virtuals
+    ?? parentOptions?.virtuals
     ?? undefined;
 
   if (virtuals || (getters && virtuals !== false)) {

test/document.test.js

@@ -13750,6 +13750,38 @@ describe('document', function() {
       /Test error in post deleteOne hook/
     );
   });
+
+  it('applies virtuals to subschemas if top-level schema has virtuals: true (gh-14771)', function() {
+    const userLabSchema = new mongoose.Schema({
+      capacityLevel: Number
+    });
+
+    userLabSchema.virtual('capacityLevelCeil').get(function() {
+      return Math.ceil(this.capacityLevel);
+    });
+
+    const labPlotSchema = new mongoose.Schema({
+      plotId: Number,
+      lab: userLabSchema
+    });
+
+    const userSchema = new mongoose.Schema({
+      username: String,
+      labPlots: [labPlotSchema]
+    }, { toObject: { virtuals: true }, toJSON: { virtuals: true } });
+
+    const User = db.model('User', userSchema);
+
+    const doc = new User({
+      username: 'test',
+      labPlots: [{
+        plotId: 1,
+        lab: { capacityLevel: 3.14 }
+      }]
+    });
+    assert.strictEqual(doc.toObject().labPlots[0].lab.capacityLevelCeil, 4);
+    assert.strictEqual(doc.toJSON().labPlots[0].lab.capacityLevelCeil, 4);
+  });
 });
 
 describe('Check if instance function that is supplied in schema option is available', function() {