Don't patch fetch globally, import patched function where needed inst…

…ead.

We'll export a `fetch` function apps can import too. This can be necessary if an app,
for example, is doing a manual `fetch` and it wants to prevent a reflected broadcast
triggered by that request.

We'll also make rails/request use the Turbo fetch version when available. That will be
the preferred form. In general, we don't want apps to care about having to import or
use Turbo's `fetch`, but it will be available for the cases an app needs it.

We'll also expose the patched version via `Turbo.fetch`.

See discussion #1019 (review)

src/core/drive/preloader.js

@@ -1,4 +1,5 @@
 import { PageSnapshot } from "./page_snapshot"
+import { fetch } from "../../http/fetch"
 
 export class Preloader {
   selector = "a[data-turbo-preload]"

src/core/index.js

@@ -3,10 +3,11 @@ import { PageRenderer } from "./drive/page_renderer"
 import { PageSnapshot } from "./drive/page_snapshot"
 import { FrameRenderer } from "./frames/frame_renderer"
 import { FormSubmission } from "./drive/form_submission"
+import { fetch } from "../http/fetch"
 
 const session = new Session()
 const { cache, navigator } = session
-export { navigator, session, cache, PageRenderer, PageSnapshot, FrameRenderer }
+export { navigator, session, cache, PageRenderer, PageSnapshot, FrameRenderer, fetch }
 
 export { StreamActions } from "./streams/stream_actions"
 

src/http/recent_fetch_requests.js → src/http/fetch.js

@@ -1,14 +1,12 @@
 import { uuid } from "../util"
 
-const originalFetch = window.fetch
-
-window.fetch = async function(url, options = {}) {
+export function fetch(url, options = {}) {
   const modifiedHeaders = new Headers(options.headers || {})
   const requestUID = uuid()
   window.Turbo.session.recentRequests.add(requestUID)
   modifiedHeaders.append("X-Turbo-Request-Id", requestUID)
 
-  return originalFetch(url, {
+  return window.fetch(url, {
     ...options,
     headers: modifiedHeaders
   })

src/http/fetch_request.js

@@ -1,6 +1,7 @@
 import { FetchResponse } from "./fetch_response"
 import { expandURL } from "../core/url"
 import { dispatch } from "../util"
+import { fetch } from "./fetch"
 
 export function fetchMethodFromString(method) {
   switch (method.toLowerCase()) {

src/index.js

@@ -1,7 +1,6 @@
 import "./polyfills"
 import "./elements"
 import "./script_warning"
-import "./http/recent_fetch_requests"
 
 import * as Turbo from "./core"
 

src/tests/functional/page_refresh_stream_action_tests.js

@@ -49,7 +49,7 @@ async function textContent(page) {
 
 async function fetchRequestId(page) {
   return await page.evaluate(async () => {
-    const response = await window.fetch("/__turbo/request_id_header")
+    const response = await window.Turbo.fetch("/__turbo/request_id_header")
     return response.text()
   })
 }