fix: add more measures to prevent using data-cache for blob operations (#2775)

Author: pieh

src/run/handlers/server.ts

@@ -13,12 +13,15 @@ import {
   setCacheTagsHeaders,
   setVaryHeaders,
 } from '../headers.js'
+import { setFetchBeforeNextPatchedIt } from '../regional-blob-store.cjs'
 import { nextResponseProxy } from '../revalidate.js'
 
 import { getLogger, type RequestContext } from './request-context.cjs'
 import { getTracer } from './tracer.cjs'
 import { setupWaitUntil } from './wait-until.cjs'
 
+setFetchBeforeNextPatchedIt(globalThis.fetch)
+
 const nextImportPromise = import('../next.cjs')
 
 setupWaitUntil()

src/run/regional-blob-store.cts

@@ -1,11 +1,62 @@
 import { getDeployStore, GetWithMetadataOptions, Store } from '@netlify/blobs'
 
-const fetchBeforeNextPatchedIt = globalThis.fetch
+const FETCH_BEFORE_NEXT_PATCHED_IT = Symbol.for('nf-not-patched-fetch')
+const extendedGlobalThis = globalThis as typeof globalThis & {
+  [FETCH_BEFORE_NEXT_PATCHED_IT]?: typeof globalThis.fetch
+}
+
+/**
+ * Attempt to extract original fetch in case it was patched by Next.js already
+ *
+ * @see github.com/vercel/next.js/blob/fa214c74c1d8023098c0e94e57f917ef9f1afd1a/packages/next/src/server/lib/patch-fetch.ts#L986
+ */
+function attemptToGetOriginalFetch(
+  fetch: typeof globalThis.fetch & {
+    _nextOriginalFetch?: typeof globalThis.fetch
+  },
+) {
+  return fetch._nextOriginalFetch ?? fetch
+}
+
+function forceOptOutOfUsingDataCache(fetch: typeof globalThis.fetch): typeof globalThis.fetch {
+  return (input, init) => {
+    return fetch(input, {
+      ...init,
+      next: {
+        ...init?.next,
+        // setting next.internal = true should prevent from trying to use data cache
+        // https://github.com/vercel/next.js/blob/fa214c74c1d8023098c0e94e57f917ef9f1afd1a/packages/next/src/server/lib/patch-fetch.ts#L174
+        // https://github.com/vercel/next.js/blob/fa214c74c1d8023098c0e94e57f917ef9f1afd1a/packages/next/src/server/lib/patch-fetch.ts#L210-L213
+        // this is last line of defense in case we didn't manage to get unpatched fetch that will not affect
+        // fetch if it's unpatched so it should be safe to apply always if we aren't sure if we use patched fetch
+
+        // @ts-expect-error - this is an internal field that Next.js doesn't add to its global
+        // type overrides for RequestInit type (like `next.revalidate` or `next.tags`)
+        internal: true,
+      },
+    })
+  }
+}
+
+export const setFetchBeforeNextPatchedIt = (fetch: typeof globalThis.fetch) => {
+  // we store in globalThis in case we have multiple copies of this module
+  // just as precaution
+
+  extendedGlobalThis[FETCH_BEFORE_NEXT_PATCHED_IT] = forceOptOutOfUsingDataCache(
+    attemptToGetOriginalFetch(fetch),
+  )
+}
+
+const fetchBeforeNextPatchedItFallback = forceOptOutOfUsingDataCache(
+  attemptToGetOriginalFetch(globalThis.fetch),
+)
+const getFetchBeforeNextPatchedIt = () =>
+  extendedGlobalThis[FETCH_BEFORE_NEXT_PATCHED_IT] ?? fetchBeforeNextPatchedItFallback
 
 export const getRegionalBlobStore = (args: GetWithMetadataOptions = {}): Store => {
   return getDeployStore({
     ...args,
-    fetch: fetchBeforeNextPatchedIt,
+    fetch: getFetchBeforeNextPatchedIt(),
     region: process.env.USE_REGIONAL_BLOBS?.toUpperCase() === 'TRUE' ? undefined : 'us-east-2',
   })
 }