Check to see whether storage is available before interacting with it (#9)

* Check to see whether storage is available before interacting with it

* Version bump: 2.0.2

Author: dpikt

__mocks__/lodash/once.js

@@ -0,0 +1,3 @@
+
+// Mock implementation returns the same function.
+module.exports = func => func

package.json

@@ -1,6 +1,6 @@
 {
   "name": "redux-sessions",
-  "version": "2.0.1",
+  "version": "2.0.2",
   "description": "Redux action creators for storing session state",
   "main": "lib/index.js",
   "scripts": {

src/persistenceHelpers.js

@@ -38,6 +38,11 @@ function persistStorageKey (userType) {
 // Loads the redux state from local / session storage.
 // We use the storage prefix to figure out which values we've saved.
 export function loadSessionState () {
+  if (!storage.isAvailable()) {
+    // eslint-disable-next-line
+    console.warn('Storage is unavailable, skipping session state load.')
+    return {}
+  }
   const storageKeys = storage.getAllKeys().filter(key => key.startsWith(STORAGE_PREFIX))
   const userTypes = uniq(storageKeys.map(getUserTypeFromStorageKey))
   const state = {}
@@ -50,6 +55,11 @@ export function loadSessionState () {
 
 // Saves the redux state to local / session storage.
 export function saveSessionState (state) {
+  if (!storage.isAvailable()) {
+    // eslint-disable-next-line
+    console.warn('Storage is unavailable, skipping session state save.')
+    return
+  }
   return map(state, ({ token, persist }, userType) => {
     storage.setItem(tokenStorageKey(userType), token, { persist })
     storage.setItem(persistStorageKey(userType), persist, { persist })

src/utils/storage.js

@@ -1,7 +1,20 @@
-import { uniq, merge, keys } from 'lodash'
+import { uniq, merge, keys, once } from 'lodash'
 
 // Unified interface for local and session storage
 
+// Returns true if local storage is available
+export const isAvailable = once(() => {
+  try {
+    const key = '__TEST__'
+    localStorage.setItem(key, key)
+    localStorage.getItem(key, key)
+    localStorage.removeItem(key)
+    return true
+  } catch (e) {
+    return false
+  }
+})
+
 // Get item from local storage, falling back to session storage
 export function getItem (key) {
   return localStorage.getItem(key) || sessionStorage.getItem(key)

test/persistenceHelpers.test.js

@@ -6,6 +6,8 @@ beforeEach(() => {
   sessionStorage.clear()
 })
 
+// Note- lodash "once" is mocked to simulate each function being run in a new context.
+
 describe('loadSessionState()', () => {
   it('loads session state from localStorage and sessionStorage', () => {
     const advisorToken = 'foo'
@@ -23,6 +25,19 @@ describe('loadSessionState()', () => {
       client: { token: clientToken, persist: clientPersist } 
     })
   })
+  describe('with prohibited localStorage', () => {
+    beforeAll(() => {
+      saveSessionState({ advisor: { token: 'foo', persist: true } })
+      window.getItem = Storage.prototype.getItem
+      Storage.prototype.getItem = () => { throw new Error('No access.') }
+    })
+    it('fails gracefully', () => {
+      expect(() => loadSessionState()).not.toThrow()
+    })
+    afterAll(() => {
+      Storage.prototype.getItem = window.getItem
+    })
+  })
 })
 
 describe('saveSessionState()', () => {
@@ -41,6 +56,18 @@ describe('saveSessionState()', () => {
     expect(sessionStorage.getItem('redux-sessions:token:client')).toEqual(clientToken)
     expect(sessionStorage.getItem('redux-sessions:persist:client')).toEqual(null)
   })
+  describe('with prohibited localStorage', () => {
+    beforeAll(() => {
+      window.setItem = Storage.prototype.setItem
+      Storage.prototype.setItem = () => { throw new Error('No access.') }
+    })
+    it('fails gracefully', () => {
+      expect(() => saveSessionState({ advisor: { token: 'foo', persist: true } })).not.toThrow()
+    })
+    afterAll(() => {
+      Storage.prototype.setItem = window.setItem
+    })
+  })
 })
 
 test('persistence helpers are reciprocal', () => {