fix: remove undefined id on deserialized data when the input has no id (#131)

* test: add a failing test on the presence of an `id` property on deserialized data when the input has no `id`
* fix: remove `id: undefined` from deserialized output when the input data had no `id`

Author: medfreeman

Diff for: lib/JSONAPISerializer.js

@@ -385,7 +385,9 @@ module.exports = class JSONAPISerializer {
     const options = this.schemas[type][schema];
 
     let deserializedData = {};
-    deserializedData[options.id] = data.id || undefined;
+    if (data.id !== undefined) {
+      deserializedData[options.id] = data.id;
+    }
 
     if (data.attributes && options.whitelistOnDeserialize.length) {
       data.attributes = pick(data.attributes, options.whitelistOnDeserialize);

Diff for: test/unit/JSONAPISerializer.test.js

@@ -2961,6 +2961,22 @@ describe('JSONAPISerializer', function() {
 
       done();
     });
+
+    it("should return deserialized data without 'id' for a single data without 'id'", function(done) {
+      const singleData = {
+        data: {
+          type: 'article',
+          attributes: {
+            title: 'JSON API paints my bikeshed!',
+          }
+        }
+      };
+      const deserializedData = Serializer.deserialize(typeOption, singleData);
+
+      expect(deserializedData).to.not.have.property('id');
+      expect(deserializedData).to.have.property('title').to.eql('JSON API paints my bikeshed!');
+      done();
+    });
   });
 
   describe('serializeError', function() {