From d756384b6c652c29bb5f086443f37883d299f147 Mon Sep 17 00:00:00 2001
From: Mihail Diordiev <zalmoxisus@gmail.com>
Date: Sat, 30 Jan 2016 15:11:54 +0200
Subject: [PATCH 1/3] Throw if the reducer passed to `replaceReducer()` is not
 a function

---
 src/instrument.js | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/instrument.js b/src/instrument.js
index e8c47f0f..a4abed96 100644
--- a/src/instrument.js
+++ b/src/instrument.js
@@ -336,6 +336,9 @@ function unliftStore(liftedStore, liftReducer) {
 export default function instrument(monitorReducer = () => null) {
   return createStore => (reducer, initialState, enhancer) => {
     function liftReducer(r) {
+      if (typeof r !== 'function') {
+        throw new Error('Expected the nextReducer to be a function.')
+      }
       return liftReducerWith(r, initialState, monitorReducer);
     }
 

From a3d053880c1a9846f5fcacff55be9046b202e4d4 Mon Sep 17 00:00:00 2001
From: Zalmoxisus <zalmoxisus@gmail.com>
Date: Sat, 30 Jan 2016 15:52:01 +0200
Subject: [PATCH 2/3] Add a test for 'Expected the nextReducer to be a
 function.' and fix ESLint

---
 src/instrument.js       | 2 +-
 test/instrument.spec.js | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/instrument.js b/src/instrument.js
index a4abed96..a886b16a 100644
--- a/src/instrument.js
+++ b/src/instrument.js
@@ -337,7 +337,7 @@ export default function instrument(monitorReducer = () => null) {
   return createStore => (reducer, initialState, enhancer) => {
     function liftReducer(r) {
       if (typeof r !== 'function') {
-        throw new Error('Expected the nextReducer to be a function.')
+        throw new Error('Expected the nextReducer to be a function.');
       }
       return liftReducerWith(r, initialState, monitorReducer);
     }
diff --git a/test/instrument.spec.js b/test/instrument.spec.js
index 9db18896..412d36db 100644
--- a/test/instrument.spec.js
+++ b/test/instrument.spec.js
@@ -322,4 +322,10 @@ describe('instrument', () => {
       expect(importMonitoredLiftedStore.getState()).toEqual(exportedState);
     });
   });
+
+  it('throws if reducer is not a function', () => {
+    expect(() =>
+      instrument()(createStore)()
+    ).toThrow('Expected the nextReducer to be a function.');
+  });
 });

From e82ef7de59526632117e749f7787df1515f68cd0 Mon Sep 17 00:00:00 2001
From: Zalmoxisus <zalmoxisus@gmail.com>
Date: Tue, 2 Feb 2016 18:07:58 +0200
Subject: [PATCH 3/3] Throw if there are more than one instrument enhancer
 included

---
 src/instrument.js       | 4 ++++
 test/instrument.spec.js | 7 ++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/instrument.js b/src/instrument.js
index a886b16a..00b74f05 100644
--- a/src/instrument.js
+++ b/src/instrument.js
@@ -343,6 +343,10 @@ export default function instrument(monitorReducer = () => null) {
     }
 
     const liftedStore = createStore(liftReducer(reducer), undefined, enhancer);
+    if (liftedStore.liftedStore) {
+      throw new Error('DevTools instrument shouldn\'t be included more than once. ' +
+        'Check your store configuration.');
+    }
     return unliftStore(liftedStore, liftReducer);
   };
 }
diff --git a/test/instrument.spec.js b/test/instrument.spec.js
index 412d36db..735024af 100644
--- a/test/instrument.spec.js
+++ b/test/instrument.spec.js
@@ -1,5 +1,5 @@
 import expect, { spyOn } from 'expect';
-import { createStore } from 'redux';
+import { createStore, compose } from 'redux';
 import instrument, { ActionCreators } from '../src/instrument';
 
 function counter(state = 0, action) {
@@ -328,4 +328,9 @@ describe('instrument', () => {
       instrument()(createStore)()
     ).toThrow('Expected the nextReducer to be a function.');
   });
+  it('throws if there are more than one instrument enhancer included', () => {
+    expect(() => {
+      store = createStore(counter, undefined, compose(instrument(), instrument()));
+    }).toThrow('DevTools instrument shouldn\'t be included more than once. Check your store configuration.');
+  });
 });