Don't depend on console object

Fixes #1311

Author: gaearon

src/combineReducers.js

@@ -2,8 +2,7 @@ import { ActionTypes } from './createStore'
 import isPlainObject from './utils/isPlainObject'
 import mapValues from './utils/mapValues'
 import pick from './utils/pick'
-
-/* eslint-disable no-console */
+import warning from './utils/warning'
 
 function getUndefinedStateErrorMessage(key, action) {
   var actionType = action && action.type
@@ -112,7 +111,7 @@ export default function combineReducers(reducers) {
     if (process.env.NODE_ENV !== 'production') {
       var warningMessage = getUnexpectedStateShapeWarningMessage(state, finalReducers, action)
       if (warningMessage) {
-        console.error(warningMessage)
+        warning(warningMessage)
       }
     }
 

src/index.js

@@ -3,6 +3,7 @@ import combineReducers from './combineReducers'
 import bindActionCreators from './bindActionCreators'
 import applyMiddleware from './applyMiddleware'
 import compose from './compose'
+import warning from './utils/warning'
 
 /*
 * This is a dummy function to check if the function name has been altered by minification.
@@ -11,15 +12,13 @@ import compose from './compose'
 function isCrushed() {}
 
 if (isCrushed.name !== 'isCrushed' && process.env.NODE_ENV !== 'production') {
-  /*eslint-disable no-console */
-  console.error(
-    'You are currently using minified code outside of NODE_ENV === \'production\'. ' + 
-    'This means that you are running a slower development build of Redux. ' + 
-    'You can use loose-envify (https://github.com/zertosh/loose-envify) for browserify ' + 
-    'or DefinePlugin for webpack (http://stackoverflow.com/questions/30030031) ' + 
+  warning(
+    'You are currently using minified code outside of NODE_ENV === \'production\'. ' +
+    'This means that you are running a slower development build of Redux. ' +
+    'You can use loose-envify (https://github.com/zertosh/loose-envify) for browserify ' +
+    'or DefinePlugin for webpack (http://stackoverflow.com/questions/30030031) ' +
     'to ensure you have the correct code for your production build.'
-  ) 
-  /*eslint-enable */
+  )
 }
 
 export {

src/utils/warning.js

@@ -0,0 +1,20 @@
+/**
+ * Prints a warning in the console if it exists.
+ *
+ * @param {String} message The warning message.
+ * @returns {void}
+ */
+export default function warning(message) {
+  /* eslint-disable no-console */
+  if (typeof console !== 'undefined' && typeof console.error === 'function') {
+    console.error(message)
+  }
+  /* eslint-enable no-console */
+  try {
+    // This error was thrown as a convenience so that you can use this stack
+    // to find the callsite that caused this warning to fire.
+    throw new Error(message)
+  /* eslint-disable no-empty */
+  } catch (e) { }
+  /* eslint-enable no-empty */
+}

test/utils/warning.spec.js

@@ -0,0 +1,36 @@
+import expect from 'expect'
+import warning from '../../src/utils/warning'
+
+describe('Utils', () => {
+  describe('warning', () => {
+    it('calls console.error when available', () => {
+      const spy = expect.spyOn(console, 'error')
+      try {
+        warning('Test')
+        expect(spy.calls[0].arguments[0]).toBe('Test')
+      } finally {
+        spy.restore()
+      }
+    })
+
+    it('does not throw when console.error is not available', () => {
+      const realConsole = global.console
+      Object.defineProperty(global, 'console', { value: {} })
+      try {
+        expect(() => warning('Test')).toNotThrow()
+      } finally {
+        Object.defineProperty(global, 'console', { value: realConsole })
+      }
+    })
+
+    it('does not throw when console is not available', () => {
+      const realConsole = global.console
+      Object.defineProperty(global, 'console', { value: undefined })
+      try {
+        expect(() => warning('Test')).toNotThrow()
+      } finally {
+        Object.defineProperty(global, 'console', { value: realConsole })
+      }
+    })
+  })
+})