test: add test case for vercel#1974 (vercel#2005)

promer94 · web-flow · commit d676bb932293 · 2022-06-01T14:56:17.000+02:00
diff --git a/core/use-swr.ts b/core/use-swr.ts
@@ -278,7 +278,6 @@ export const useSWRHandler = <Data = any, Error = any>(
       }
       try {
         if (shouldStartNewRequest) {
-          // TODO: should add a test case for this https://github.com/vercel/swr/issues/1974
           setCache(initialState)
           // If no cache being rendered currently (it shows a blank page),
           // we trigger the loading slow event.
diff --git a/test/use-swr-integration.test.tsx b/test/use-swr-integration.test.tsx
@@ -1,5 +1,5 @@
 import { act, screen, fireEvent } from '@testing-library/react'
-import React, { useState, useEffect } from 'react'
+import React, { useState, useEffect, Profiler } from 'react'
 import useSWR from 'swr'
 import {
   createResponse,
@@ -432,4 +432,40 @@ describe('useSWR', () => {
     await act(() => sleep(20))
     screen.getByText('data: 1')
   })
+  it('Nested SWR hook should only do loading once', async () => {
+    const key = createKey()
+    let count = 0
+    const ChildComponent = () => {
+      const { data } = useSWR(key, (_) => createResponse(_, { delay: 100 }))
+      return (
+        <div id="child">
+          {data}
+        </div>
+      )
+    }
+    const NestedRender = () => {
+      const { data, isValidating } = useSWR(key, (_) => createResponse(_, { delay: 50 }))
+      if (isValidating) {
+        return <div>loading</div>
+      }
+      return (
+        <div>
+          <div id="parent">{data}</div>
+          <ChildComponent></ChildComponent>
+        </div>
+      )
+    }
+    const Page = () => (
+      <Profiler id={key} onRender={() => {
+        count += 1
+      }}>
+        <NestedRender></NestedRender>
+      </Profiler>
+    )
+    renderWithConfig(<Page />)
+    await screen.findByText(`loading`)
+    await screen.findAllByText(key)
+    await act(() => sleep(150))
+    expect(count).toBe(2)
+  })
 })

Original file line number	Diff line number	Diff line change
`@@ -278,7 +278,6 @@ export const useSWRHandler = <Data = any, Error = any>(`
`278`	`278`	`}`
`279`	`279`	`try {`
`280`	`280`	`if (shouldStartNewRequest) {`
`281`		`- // TODO: should add a test case for this https://github.com/vercel/swr/issues/1974`
`282`	`281`	`setCache(initialState)`
`283`	`282`	`// If no cache being rendered currently (it shows a blank page),`
`284`	`283`	`// we trigger the loading slow event.`