Merge pull request #13126 from lpizzinidev/gh-13125

fix(aggregate): added `await` to prevent exception in aggregate exec

Author: vkarpov15

lib/aggregate.js

@@ -1049,7 +1049,7 @@ Aggregate.prototype.exec = async function exec() {
   const options = clone(this.options || {});
   let result;
   try {
-    const cursor = collection.aggregate(this._pipeline, options);
+    const cursor = await collection.aggregate(this._pipeline, options);
     result = await cursor.toArray();
   } catch (error) {
     await new Promise((resolve, reject) => {

test/aggregate.test.js

@@ -1242,4 +1242,22 @@ describe('aggregate: ', function() {
     });
   });
 
+  it('should not throw error if database connection has not been established (gh-13125)', async function() {
+    const m = new mongoose.Mongoose();
+    const mySchema = new Schema({ test: String });
+    const M = m.model('Test', mySchema);
+
+    const aggregate = M.aggregate();
+    aggregate.match({ $match: { foo: 'bar' } });
+    
+    const p = aggregate.exec();
+    
+    await new Promise(resolve => setTimeout(resolve, 0));
+    await m.connect(start.uri);
+
+    assert.doesNotThrow(async function() {
+      await p;
+    });
+    await m.disconnect();
+  });
 });