fix: mongoose schema default should not mutate original object

Closes Automattic#12102
lpizzinidev · Jul 16, 2022 · 49aa88d · 49aa88d
1 parent 86f66b0
commit 49aa88d
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Showing 2 changed files with 29 additions and 2 deletions.
diff --git a/lib/document.js b/lib/document.js
@@ -1149,8 +1149,10 @@ Document.prototype.$set = function $set(path, val, type, options) {
       }
 
       if (utils.isNonBuiltinObject(valForKey) && pathtype === 'nested') {
-        $applyDefaultsToNested(path[key], prefix + key, this);
-        this.$set(prefix + key, path[key], constructing, Object.assign({}, options, { _skipMarkModified: true }));
+        // Create a copy of the object to avoid editing the original
+        const pathKey = { ...path[key] }
+        $applyDefaultsToNested(pathKey, prefix + key, this);
+        this.$set(prefix + key, pathKey, constructing, Object.assign({}, options, { _skipMarkModified: true }));
         continue;
       } else if (strict) {
         // Don't overwrite defaults with undefined keys (gh-3981) (gh-9039)

diff --git a/test/document.test.js b/test/document.test.js
@@ -2332,6 +2332,31 @@ describe('document', function() {
       assert.equal(res.test, 'test');
       assert.ok(!res.subDoc);
     });
+
+    it('original object nested fields should not be mutated by mongoose schema defaults (gh-12102)', function() {
+      const schema = new mongoose.Schema({
+        topLevelField1: {
+          nestedField1: String,
+          nestedField2: {type: String, default: 'defValue'}
+        },
+        topLevelField2: {type: String, default: 'defValue'}
+      })
+
+      const Model = db.model('Test', schema);
+
+      const originalData = {
+        topLevelField1: {
+          nestedField1: 'provided'
+        }
+      }
+
+      const model = new Model(originalData);
+      assert.deepEqual(originalData, {
+        topLevelField1: {
+          nestedField1: 'provided'
+        }
+      })
+    });  
   });
 
   describe('error processing (gh-2284)', async function() {