Ensure Storage is open before using it

Always await the promise returned by `caches.open` before using the
resulting `Cache` object. This prevents race conditions where the
`Cache` object is used before it is ready.

src/core/drive/cache_stores/disk_store.ts

@@ -3,7 +3,7 @@ import { PageSnapshot } from "../page_snapshot"
 
 export class DiskStore extends CacheStore {
   _version = "v1"
-  storage!: Cache
+  storage!: Promise<Cache>
 
   constructor() {
     super()
@@ -12,45 +12,54 @@ export class DiskStore extends CacheStore {
       throw new Error("windows.caches is undefined. CacheStore requires a secure context.")
     }
 
-    this.initialize()
-  }
-
-  async initialize() {
-    this.storage = await caches.open(`turbo-${this.version}`)
+    this.storage = this.openStorage()
   }
 
   async has(location: URL) {
-    return (await this.storage.match(location)) !== undefined
+    const storage = await this.openStorage()
+    return (await storage.match(location)) !== undefined
   }
 
   async get(location: URL) {
-    const response = await this.storage.match(location)
+    const storage = await this.openStorage()
+    const response = await storage.match(location)
+
     if (response && response.ok) {
       const html = await response.text()
       return PageSnapshot.fromHTMLString(html)
     }
   }
 
   async put(location: URL, snapshot: PageSnapshot) {
+    const storage = await this.openStorage()
+
     const response = new Response(snapshot.html, {
       status: 200,
       statusText: "OK",
       headers: {
         "Content-Type": "text/html",
       },
     })
-    await this.storage.put(location, response)
+    await storage.put(location, response)
     return snapshot
   }
 
   async clear() {
-    const keys = await this.storage.keys()
-    await Promise.all(keys.map((key) => this.storage.delete(key)))
+    const storage = await this.openStorage()
+    const keys = await storage.keys()
+    await Promise.all(keys.map((key) => storage.delete(key)))
+  }
+
+  openStorage() {
+    this.storage ||= caches.open(`turbo-${this.version}`)
+    return this.storage
   }
 
   set version(value: string) {
-    this._version = value
-    this.initialize()
+    if (value !== this._version) {
+      this._version = value
+      this.storage ||= caches.open(`turbo-${this.version}`)
+    }
   }
 
   get version() {

src/tests/functional/disk_cache_tests.ts

@@ -7,7 +7,7 @@ test.beforeEach(async ({ page }) => {
   await page.goto(path)
 })
 
-test("test stores pages in the disk cache", async ({ page }) => {
+test("stores pages in the disk cache", async ({ page }) => {
   await assertCachedURLs(page, [])
 
   page.click("#second-link")