fix(code-block): fix local-storage breakage (#735)

* fix(code-block): check before accessing local storage

* chore(code-block): add changeset

.changeset/shaggy-readers-brake.md

@@ -0,0 +1,5 @@
+---
+'@hashicorp/react-code-block': patch
+---
+
+Fixes an issue where code-block would throw an error and potentially break the consuming app if local storage is disabled.

packages/code-block/provider/index.tsx

@@ -1,4 +1,5 @@
 import { createContext, useState, useContext, useEffect, useMemo } from 'react'
+import safeLocalStorage from '../utils/safe-local-storage'
 
 export function useTabGroups() {
   return useContext(CodeTabsContext)
@@ -42,13 +43,13 @@ export default function CodeTabsProvider({ children }) {
     // then save it to local storage
     if (updatedPreferences.length > 0) {
       const storedValueJson = JSON.stringify(updatedPreferences)
-      window.localStorage.setItem(LOCAL_STORAGE_KEY, storedValueJson)
+      safeLocalStorage.setItem(LOCAL_STORAGE_KEY, storedValueJson)
     }
   }, [activeTabGroup])
 
   // Load activeTabGroup from cookie, if available
   useEffect(() => {
-    const maybeStoredValue = window.localStorage.getItem(LOCAL_STORAGE_KEY)
+    const maybeStoredValue = safeLocalStorage.getItem(LOCAL_STORAGE_KEY)
     if (maybeStoredValue) {
       // Try / catch in case JSON.parse fails
       try {

packages/code-block/utils/safe-local-storage.ts

@@ -0,0 +1,40 @@
+/**
+ * Returns `true` if window.localStorage can be used,
+ * or `false` otherwise.
+ *
+ * Based on:
+ * https://github.com/Modernizr/Modernizr/blob/master/feature-detects/storage/localstorage.js
+ */
+function isLocalStorageAvailable() {
+  const test = 'test'
+  try {
+    window.localStorage.setItem(test, test)
+    window.localStorage.getItem(test)
+    window.localStorage.removeItem(test)
+    return true
+  } catch (e) {
+    return false
+  }
+}
+
+/**
+ * Gets an item from local storage, if available.
+ * Safely returns `null` if local storage is unavailable.
+ */
+function getItem(key: string) {
+  if (!isLocalStorageAvailable()) return null
+  return window.localStorage.getItem(key)
+}
+
+/**
+ * Sets an item in local storage.
+ * Safely returns `null` if local storage is unavailable.
+ */
+function setItem(key: string, value: string) {
+  if (!isLocalStorageAvailable()) return null
+  return window.localStorage.setItem(key, value)
+}
+
+const safeLocalStorage = { getItem, setItem }
+
+export default safeLocalStorage