fix(handleAction): Add descriptive error for missing or invalid actions

package.json

@@ -50,12 +50,13 @@
     "eslint-config-airbnb-base": "^1.0.3",
     "eslint-plugin-import": "^1.5.0",
     "eslint-watch": "^2.1.13",
-    "flux-standard-action": "^0.6.0",
     "mocha": "^2.2.5",
     "rimraf": "^2.5.3",
     "webpack": "^1.13.1"
   },
   "dependencies": {
+    "flux-standard-action": "^1.0.0",
+    "invariant": "^2.2.1",
     "lodash": "^4.13.1",
     "reduce-reducers": "^0.1.0"
   }

src/__tests__/handleAction-test.js

@@ -1,4 +1,5 @@
 import { expect } from 'chai';
+import identity from 'lodash/identity';
 import { handleAction, createAction, createActions, combineActions } from '../';
 
 describe('handleAction()', () => {
@@ -195,4 +196,36 @@ describe('handleAction()', () => {
         .to.deep.equal({ number: 3 });
     });
   });
+
+  describe('with invalid actions', () => {
+    it('should throw a descriptive error when the action object is missing', () => {
+      const reducer = handleAction(createAction('ACTION_1'), identity);
+      expect(
+        () => reducer(undefined)
+      ).to.throw(
+        Error,
+        'The FSA spec mandates an action object with a type. Try using the createAction(s) method.'
+      );
+    });
+
+    it('should throw a descriptive error when the action type is missing', () => {
+      const reducer = handleAction(createAction('ACTION_1'), identity);
+      expect(
+        () => reducer(undefined, {})
+      ).to.throw(
+        Error,
+        'The FSA spec mandates an action object with a type. Try using the createAction(s) method.'
+      );
+    });
+
+    it('should throw a descriptive error when the action type is not a string or symbol', () => {
+      const reducer = handleAction(createAction('ACTION_1'), identity);
+      expect(
+        () => reducer(undefined, { type: false })
+      ).to.throw(
+        Error,
+        'The FSA spec mandates an action object with a type. Try using the createAction(s) method.'
+      );
+    });
+  });
 });

src/handleAction.js

@@ -2,6 +2,8 @@ import isFunction from 'lodash/isFunction';
 import identity from 'lodash/identity';
 import isNil from 'lodash/isNil';
 import includes from 'lodash/includes';
+import invariant from 'invariant';
+import { isFSA } from 'flux-standard-action';
 import { ACTION_TYPE_DELIMITER } from './combineActions';
 
 export default function handleAction(actionType, reducers, defaultState) {
@@ -12,6 +14,11 @@ export default function handleAction(actionType, reducers, defaultState) {
     : [reducers.next, reducers.throw].map(reducer => (isNil(reducer) ? identity : reducer));
 
   return (state = defaultState, action) => {
+    invariant(
+      isFSA(action),
+      'The FSA spec mandates an action object with a type. Try using the createAction(s) method.'
+    );
+
     if (!includes(actionTypes, action.type.toString())) {
       return state;
     }