Dispatch turbo:before-fetch-{request,response} during preloading

Closes [hotwired#963][] Replace the raw call to `fetch` with a new `FetchRequest` instance that treats the `Preloaded` instances as its delegate. During that request's lifecycle, dispatch the `turbo:before-fetch-request` and `turbo:before-fetch-response` events with the `<a>` element as its target. Prepare the request with the [Sec-Purpose][] header in the `prepareRequest` delegate callback. Write to the snapshot cache from within the `requestSucceededWithResponse` delegate callback. [hotwired#963]: hotwired#963 [Sec-Purpose]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Sec-Purpose#prefetch
seanpdoyle · Dec 8, 2023 · f214f61 · f214f61
1 parent 098aafc
commit f214f61
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Showing 5 changed files with 43 additions and 6 deletions.
diff --git a/src/core/drive/preloader.js b/src/core/drive/preloader.js
@@ -1,5 +1,5 @@
 import { PageSnapshot } from "./page_snapshot"
-import { fetch } from "../../http/fetch"
+import { FetchMethod, FetchRequest } from "../../http/fetch_request"
 
 export class Preloader {
   selector = "a[data-turbo-preload]"
@@ -36,17 +36,37 @@ export class Preloader {
       return
     }
 
+    const fetchRequest = new FetchRequest(this, FetchMethod.get, location, new URLSearchParams(), link)
+    await fetchRequest.perform()
+  }
+
+  // Fetch request delegate
+
+  prepareRequest(fetchRequest) {
+    fetchRequest.headers["Sec-Purpose"] = "prefetch"
+  }
+
+  async requestSucceededWithResponse(fetchRequest, fetchResponse) {
     try {
-      const response = await fetch(location.toString(), { headers: { "Sec-Purpose": "prefetch", Accept: "text/html" } })
-      const responseText = await response.text()
-      const snapshot = PageSnapshot.fromHTMLString(responseText)
+      const responseHTML = await fetchResponse.responseHTML
+      const snapshot = PageSnapshot.fromHTMLString(responseHTML)
 
-      this.snapshotCache.put(location, snapshot)
+      this.snapshotCache.put(fetchRequest.url, snapshot)
     } catch (_) {
       // If we cannot preload that is ok!
     }
   }
 
+  requestStarted(fetchRequest) {}
+
+  requestErrored(fetchRequest) {}
+
+  requestFinished(fetchRequest) {}
+
+  requestPreventedHandlingResponse(fetchRequest, fetchResponse) {}
+
+  requestFailedWithResponse(fetchRequest, fetchResponse) {}
+
   #preloadAll = () => {
     this.preloadOnLoadLinksForView(document.body)
   }

diff --git a/src/tests/fixtures/hot_preloading.html b/src/tests/fixtures/hot_preloading.html
@@ -5,6 +5,7 @@
   <meta charset="utf-8">
   <title>Page That Links to Preloading Page</title>
   <script src="/dist/turbo.es2017-umd.js" data-turbo-track="reload"></script>
+  <script src="/src/tests/fixtures/test.js"></script>
 </head>
 
 <body>

diff --git a/src/tests/fixtures/preloaded.html b/src/tests/fixtures/preloaded.html
@@ -5,6 +5,7 @@
   <meta charset="utf-8">
   <title>Preloaded Page</title>
   <script src="/dist/turbo.es2017-umd.js" data-turbo-track="reload"></script>
+  <script src="/src/tests/fixtures/test.js"></script>
 </head>
 
 <body>

diff --git a/src/tests/fixtures/preloading.html b/src/tests/fixtures/preloading.html
@@ -5,6 +5,7 @@
   <meta charset="utf-8">
   <title>Preloading Page</title>
   <script src="/dist/turbo.es2017-umd.js" data-turbo-track="reload"></script>
+    <script src="/src/tests/fixtures/test.js"></script>
 </head>
 
 <body>

diff --git a/src/tests/functional/preloader_tests.js b/src/tests/functional/preloader_tests.js
@@ -1,6 +1,6 @@
 import { test } from "@playwright/test"
 import { assert } from "chai"
-import { nextEventOnTarget } from "../helpers/page"
+import { nextEventNamed, nextEventOnTarget } from "../helpers/page"
 
 test("preloads snapshot on initial load", async ({ page }) => {
   // contains `a[rel="preload"][href="http://localhost:9000/src/tests/fixtures/preloaded.html"]`
@@ -12,6 +12,20 @@ test("preloads snapshot on initial load", async ({ page }) => {
   assert.ok(await urlInSnapshotCache(page, href))
 })
 
+test("preloading dispatch turbo:before-fetch-{request,response} events", async ({ page }) => {
+  await page.goto("/src/tests/fixtures/preloading.html")
+
+  const link = await page.locator("#preload_anchor")
+  const href = await link.evaluate((link) => link.href)
+
+  const { url, fetchOptions } = await nextEventNamed(page, "turbo:before-fetch-request")
+  const { fetchResponse } = await nextEventNamed(page, "turbo:before-fetch-response")
+
+  assert.equal(href, url, "dispatches request during preloading")
+  assert.equal(fetchOptions.headers.Accept, "text/html, application/xhtml+xml")
+  assert.equal(fetchResponse.response.url, href)
+})
+
 test("preloads snapshot on page visit", async ({ page }) => {
   // contains `a[rel="preload"][href="http://localhost:9000/src/tests/fixtures/preloading.html"]`
   await page.goto("/src/tests/fixtures/hot_preloading.html")