Make payload optional (as per FSA spec) (#48)

* Make payload optional (as per FSA spec)

* When payload is null also ignore it

* merge in master branch

* Explictly check for null or undefined, was picking up some false positives with old check

Author: John Mortlock

src/__tests__/createAction-test.js

@@ -80,5 +80,41 @@ describe('createAction()', () => {
         meta: { foo: 'bar' }
       });
     });
+
+    it('sets payload only when defined', () => {
+      const action = createAction(type)();
+      expect(action).to.deep.equal({
+        type
+      });
+
+      const explictUndefinedAction = createAction(type)(undefined);
+      expect(explictUndefinedAction).to.deep.equal({
+        type
+      });
+
+      const explictNullAction = createAction(type)(null);
+      expect(explictNullAction).to.deep.equal({
+        type
+      });
+
+      const baz = '1';
+      const actionCreator = createAction(type, null, () => ({ bar: baz }));
+      expect(actionCreator()).to.deep.equal({
+        type,
+        meta: {
+          bar: '1'
+        }
+      });
+
+      const validPayload = [false, 0, ''];
+      for (let i = 0; i < validPayload.length; i++) {
+        const validValue = validPayload[i];
+        const expectPayload = createAction(type)(validValue);
+        expect(expectPayload).to.deep.equal({
+          type,
+          payload: validValue
+        });
+      }
+    });
   });
 });

src/createAction.js

@@ -9,10 +9,14 @@ export default function createAction(type, actionCreator, metaCreator) {
 
   return (...args) => {
     const action = {
-      type,
-      payload: finalActionCreator(...args)
+      type
     };
 
+    const payload = finalActionCreator(...args);
+    if (!(payload === null || payload === undefined)) {
+      action.payload = payload;
+    }
+
     if (action.payload instanceof Error) {
       // Handle FSA errors where the payload is an Error object. Set error.
       action.error = true;