Merge pull request #14202 from Automattic/vkarpov15/gh-14162

fix(discriminator): handle reusing schema with embedded discriminators defined using Schema.prototype.discriminator

Author: vkarpov15

lib/helpers/discriminator/applyEmbeddedDiscriminators.js

@@ -16,8 +16,15 @@ function applyEmbeddedDiscriminators(schema, seen = new WeakSet()) {
     if (!schemaType.schema._applyDiscriminators) {
       continue;
     }
+    if (schemaType._appliedDiscriminators) {
+      continue;
+    }
     for (const disc of schemaType.schema._applyDiscriminators.keys()) {
-      schemaType.discriminator(disc, schemaType.schema._applyDiscriminators.get(disc));
+      schemaType.discriminator(
+        disc,
+        schemaType.schema._applyDiscriminators.get(disc)
+      );
     }
+    schemaType._appliedDiscriminators = true;
   }
 }

test/document.test.js

@@ -12765,6 +12765,28 @@ describe('document', function() {
     );
   });
 
+  it('handles reusing schema with embedded discriminators defined using Schema.prototype.discriminator (gh-14162)', async function() {
+    const discriminated = new Schema({
+      type: { type: Number, required: true }
+    }, { discriminatorKey: 'type' });
+
+    discriminated.discriminator(1, new Schema({ prop1: String }));
+    discriminated.discriminator(3, new Schema({ prop2: String }));
+
+    const containerSchema = new Schema({ items: [discriminated] });
+    const containerModel = db.model('Test', containerSchema);
+    const containerModel2 = db.model('Test1', containerSchema);
+    const doc1 = new containerModel({ items: [{ type: 1, prop1: 'foo' }, { type: 3, prop2: 'bar' }] });
+    const doc2 = new containerModel2({ items: [{ type: 1, prop1: 'baz' }, { type: 3, prop2: 'qux' }] });
+    await doc1.save();
+    await doc2.save();
+
+    doc1.items.push({ type: 3, prop2: 'test1' });
+    doc2.items.push({ type: 3, prop2: 'test1' });
+    await doc1.save();
+    await doc2.save();
+  });
+
   it('can use `collection` as schema name (gh-13956)', async function() {
     const schema = new mongoose.Schema({ name: String, collection: String });
     const Test = db.model('Test', schema);