React 18: Context providers are reset to initial value in SSR during rendering #23089
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frandiox
added
React 18
|
yes, i got the same problem. when got more then 2 requests at the same time, the context providers will not work. this is my code: react / react-dom version is 18.0.0-rc.0-next-9a7e6bf0d-20220111 import http from "http";
import React from "react";
import ReactDOMServer from "react-dom/server";
class DelayClient {
public resolved?: string;
public pending?: Promise<void>
get() {
if (this.resolved) return this.resolved;
if (this.pending) return this.pending;
return this.pending = new Promise(resolve => {
setTimeout(() => {
delete this.pending;
this.resolved = "OK";
resolve();
console.log("timeout");
}, 2000);
});
}
}
const DelayContext = React.createContext<DelayClient | undefined>(undefined);
// this is the component that use delay
// when a single request coming, this is OK. delay 2 seconds then got a "OK" from context
// but if mutli request (refresh website fastly), it will delay 2 seconds then context is undefined.
const Component: React.FC = () => {
const client = React.useContext(DelayContext);
if (!client) {
return <div>context not found.</div>;
}
const result = client.get();
if (typeof result === "string") {
return <div>{result}</div>
}
throw result;
}
const app = http.createServer((req, res) => {
if (req.url !== "/") {
res.statusCode = 200;
res.end();
return;
}
// every request has a DelayClient to wait 2 seconds
// then get a "OK" from DelayClient through context
const client = new DelayClient();
const element = <html>
<head>
<title>sample</title>
</head>
<body>
<DelayContext.Provider value={client}>
<React.Suspense fallback="loading">
<Component/>
</React.Suspense>
</DelayContext.Provider>
</body>
</html>;
const { pipe } = (ReactDOMServer as any).renderToPipeableStream(element, {
onError(error: any) {
console.log("error", error);
},
onCompleteShell() {
res.writeHead(200, { "Content-Type": "text/html; charset=UTF-8" });
pipe(res);
},
});
});
app.listen(3000, () => {
console.log("app lift: http://127.0.0.1:3000/")
}); |
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Can you turn this into a failing test? Search the tests for existing tests using renderToPipeableStream. |
4 tasks
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It's supposed to get reset here when restarting work after switching between working on different tasks (whether they're part of the same request or multiple). |
frandiox
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Jan 24, 2022
gaearon
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gaearon
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Jan 24, 2022
* add failing test for renderToPipeableStream * Fix context providers in SSR when handling multiple requests. Closes #23089 * Add sibling regression test Co-authored-by: zhuyi01 <zhuyi01@ke.com> Co-authored-by: Dan Abramov <dan.abramov@me.com>
|
The fix is out in |
4 tasks
zhengjitf
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Apr 15, 2022
…k#23171) * add failing test for renderToPipeableStream * Fix context providers in SSR when handling multiple requests. Closes facebook#23089 * Add sibling regression test Co-authored-by: zhuyi01 <zhuyi01@ke.com> Co-authored-by: Dan Abramov <dan.abramov@me.com>
nevilm-lt
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Apr 22, 2022
…k#23171) * add failing test for renderToPipeableStream * Fix context providers in SSR when handling multiple requests. Closes facebook#23089 * Add sibling regression test Co-authored-by: zhuyi01 <zhuyi01@ke.com> Co-authored-by: Dan Abramov <dan.abramov@me.com>
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While testing SSR streaming in latest React 18 experimental and alpha versions, we noticed that context providers are reset to their initial values during rendering under certain conditions.
It works well when handling 1 request at a time. However, when the server gets 2 or more requests at the same time, the context providers seem to get confused. The context is correct at the beginning of the rendering for each request but it gets lost after a while.
There's a reproduction here using @gaearon 's demo: https://codesandbox.io/s/keen-snowflake-8nyo8?file=/src/data.js:1035-1082
To my understanding, since the React tree is wrapped in a provider in SSR,
useContextshould never returnnullin the server. Have a look at the terminal and see how it actually logsnullsometimes when getting multiple requests.Run the following code from the console to simulate multiple requests:
We saw this same issue in different setups, using both Webpack and Vite.
Thanks!
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