Change server actions cache default to no-store (vercel#60170)

## What?


Currently there is a bug in Server Actions when you `fetch` as it uses
the same defaults (caching when not specified) as rendering, this causes
some issues as you want to read your writes in Server Actions.

This change adds the `no-store` default for Server Actions, you can
still override it by specifying `cache: 'force-cache'` for example, but
it defaults to `cache: 'no-store'`.

Fixes NEXT-1926

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---------

Co-authored-by: Zack Tanner <zacktanner@gmail.com>

packages/next/src/server/app-render/action-handler.ts

@@ -299,6 +299,9 @@ export async function handleAction({
     )
   }
 
+  // When running actions the default is no-store, you can still `cache: 'force-cache'`
+  staticGenerationStore.fetchCache = 'default-no-store'
+
   const originDomain =
     typeof req.headers['origin'] === 'string'
       ? new URL(req.headers['origin']).host

test/e2e/app-dir/actions/app-action.test.ts

@@ -1114,5 +1114,77 @@ createNextDescribe(
         })
       })
     })
+
+    describe('caching disabled by default', () => {
+      it('should use no-store as default for server action', async () => {
+        const browser = await next.browser('/no-caching-in-actions')
+        await browser
+          .waitForElementByCss('#trigger-fetch')
+          .click()
+          .waitForElementByCss('#fetched-data')
+
+        const getNumber = async () =>
+          JSON.parse(await browser.elementByCss('#fetched-data').text())
+
+        const firstNumber = await getNumber()
+
+        await browser.waitForElementByCss('#trigger-fetch').click()
+
+        await check(async () => {
+          const newNumber = await getNumber()
+          // Expect that the number changes on each click
+          expect(newNumber).not.toBe(firstNumber)
+
+          return 'success'
+        }, 'success')
+      })
+
+      it('should not override force-cache in server action', async () => {
+        const browser = await next.browser('/no-caching-in-actions/force-cache')
+        await browser
+          .waitForElementByCss('#trigger-fetch')
+          .click()
+          .waitForElementByCss('#fetched-data')
+
+        const getNumber = async () =>
+          JSON.parse(await browser.elementByCss('#fetched-data').text())
+
+        const firstNumber = await getNumber()
+
+        await browser.waitForElementByCss('#trigger-fetch').click()
+
+        await check(async () => {
+          const newNumber = await getNumber()
+          // Expect that the number is the same on each click
+          expect(newNumber).toBe(firstNumber)
+
+          return 'success'
+        }, 'success')
+      })
+
+      // Implicit force-cache
+      it('should not override revalidate in server action', async () => {
+        const browser = await next.browser('/no-caching-in-actions/revalidate')
+        await browser
+          .waitForElementByCss('#trigger-fetch')
+          .click()
+          .waitForElementByCss('#fetched-data')
+
+        const getNumber = async () =>
+          JSON.parse(await browser.elementByCss('#fetched-data').text())
+
+        const firstNumber = await getNumber()
+
+        await browser.waitForElementByCss('#trigger-fetch').click()
+
+        await check(async () => {
+          const newNumber = await getNumber()
+          // Expect that the number is the same on each click
+          expect(newNumber).toBe(firstNumber)
+
+          return 'success'
+        }, 'success')
+      })
+    })
   }
 )

test/e2e/app-dir/actions/app/no-caching-in-actions/actions.js

@@ -0,0 +1,9 @@
+'use server'
+
+export async function getNumber() {
+  const res = await fetch(
+    'https://next-data-api-endpoint.vercel.app/api/random?no-caching-actions'
+  )
+
+  return res.text()
+}

test/e2e/app-dir/actions/app/no-caching-in-actions/force-cache/actions.js

@@ -0,0 +1,12 @@
+'use server'
+
+export async function getNumber() {
+  const res = await fetch(
+    'https://next-data-api-endpoint.vercel.app/api/random?no-caching-actions',
+    {
+      cache: 'force-cache',
+    }
+  )
+
+  return res.text()
+}

test/e2e/app-dir/actions/app/no-caching-in-actions/force-cache/page.js

@@ -0,0 +1,27 @@
+'use client'
+import { useState, useTransition } from 'react'
+import { getNumber } from './actions'
+
+export default function Page() {
+  const [isPending, startTransition] = useTransition()
+  const [result, setResult] = useState(null)
+  return (
+    <>
+      <h1>No Caching in Actions: {isPending ? 'pending' : 'not pending'}</h1>
+      {result !== null ? (
+        <pre id="fetched-data">{JSON.stringify(result)}</pre>
+      ) : null}
+      <button
+        id="trigger-fetch"
+        onClick={() =>
+          startTransition(async () => {
+            const result = await getNumber()
+            setResult(result)
+          })
+        }
+      >
+        Trigger fetch
+      </button>
+    </>
+  )
+}

test/e2e/app-dir/actions/app/no-caching-in-actions/page.js

@@ -0,0 +1,27 @@
+'use client'
+import { useState, useTransition } from 'react'
+import { getNumber } from './actions'
+
+export default function Page() {
+  const [isPending, startTransition] = useTransition()
+  const [result, setResult] = useState(null)
+  return (
+    <>
+      <h1>No Caching in Actions: {isPending ? 'pending' : 'not pending'}</h1>
+      {result !== null ? (
+        <pre id="fetched-data">{JSON.stringify(result)}</pre>
+      ) : null}
+      <button
+        id="trigger-fetch"
+        onClick={() =>
+          startTransition(async () => {
+            const result = await getNumber()
+            setResult(result)
+          })
+        }
+      >
+        Trigger fetch
+      </button>
+    </>
+  )
+}

test/e2e/app-dir/actions/app/no-caching-in-actions/revalidate/actions.js

@@ -0,0 +1,14 @@
+'use server'
+
+export async function getNumber() {
+  const res = await fetch(
+    'https://next-data-api-endpoint.vercel.app/api/random?no-caching-actions',
+    {
+      next: {
+        revalidate: 100,
+      },
+    }
+  )
+
+  return res.text()
+}

test/e2e/app-dir/actions/app/no-caching-in-actions/revalidate/page.js

@@ -0,0 +1,27 @@
+'use client'
+import { useState, useTransition } from 'react'
+import { getNumber } from './actions'
+
+export default function Page() {
+  const [isPending, startTransition] = useTransition()
+  const [result, setResult] = useState(null)
+  return (
+    <>
+      <h1>No Caching in Actions: {isPending ? 'pending' : 'not pending'}</h1>
+      {result !== null ? (
+        <pre id="fetched-data">{JSON.stringify(result)}</pre>
+      ) : null}
+      <button
+        id="trigger-fetch"
+        onClick={() =>
+          startTransition(async () => {
+            const result = await getNumber()
+            setResult(result)
+          })
+        }
+      >
+        Trigger fetch
+      </button>
+    </>
+  )
+}