Merge pull request #13322 from Automattic/IslandRhythms/gh-13274

Merge Document `$inc` calls instead of overwriting

lib/document.js

@@ -1800,7 +1800,11 @@ Document.prototype.$inc = function $inc(path, val) {
 
   if (shouldSet) {
     this.$__.primitiveAtomics = this.$__.primitiveAtomics || {};
-    this.$__.primitiveAtomics[path] = { $inc: valToInc };
+    if (this.$__.primitiveAtomics[path] == null) {
+      this.$__.primitiveAtomics[path] = { $inc: valToInc };
+    } else {
+      this.$__.primitiveAtomics[path].$inc += valToInc;
+    }
     this.markModified(path);
     this.$__setValue(path, valToSet);
   }

package.json

@@ -39,6 +39,7 @@
     "axios": "1.1.3",
     "babel-loader": "8.2.5",
     "benchmark": "2.1.4",
+    "bluebird": "3.7.2",
     "broken-link-checker": "^0.7.8",
     "buffer": "^5.6.0",
     "cheerio": "1.0.0-rc.12",

test/document.test.js

@@ -11867,6 +11867,19 @@ describe('document', function() {
       assert.ok(err);
       assert.equal(err.errors['prop'].name, 'CastError');
     });
+    it('should correctly increment even if the document has not saved after each increment gh-13274', async function() {
+      const schema = new Schema({
+        coins: Number
+      });
+      const Test = db.model('gh13274', schema);
+      await Test.create({ coins: 0 });
+      const doc = await Test.findOne();
+      doc.$inc('coins', 1000);
+      doc.$inc('coins', 2000);
+      await doc.save();
+      const check = await Test.findOne();
+      assert.equal(check.coins, 3000);
+    });
   });
 
   it('supports virtuals named `isValid` (gh-12124) (gh-6262)', async function() {