@bvaughn Mind if I take this up?

Sure

Hi @bvaughn, this issue still exists. I can try this one unless someone else is not actively working on it.

Commented: #17889 (review). I don't think this fix is correct.

Could I help here ? 🙂

Sure.

@gaearon Would it be possible to get some guidance on where to start ? I'm looking at the CodeSandbox provided to start digging in the problem and in the source possibly in ReactPartialRenderer.js and ReactPartialRendererHooks,js. Am I on the right path ?

Hey @gaearon it seems this bug may be caused by lack of isolation inside ReactPartialRendererHooks.js so when methods are executed they are changing the same variables for both renderers.
If I'll try to isolate these variables within separate class is it will be an acceptable solution?

@jeremyscatigna This sounds right. Are you still working on this?

I believe this is happening to me using NextJS as well. I'm not sure exactly why the PR hasn't been merged. Not complaining, but just letting maintainers know this appears to be impacting a usecase like mine.

No news about this issue ?

My notes on this issue.

This happens only when trying to renderToStaticMarkup(<App />); and inside App there is a useState, useReducer or useMemo that also uses renderToStaticMarkup

e.g.

import React, { useMemo, useReducer, useState } from "react";
import { renderToStaticMarkup } from "react-dom/server";

const hello = <h1>Hello Andrew!</h1>;
const reducer = (state: any) => state;

function App() {
  // Uncomment one of below lines and you will get a error
  // useMemo(() => renderToStaticMarkup(hello), []);
  // useState(() => renderToStaticMarkup(hello));
  // useReducer(reducer, "", () => renderToStaticMarkup(hello));
  return <div />;
}

renderToStaticMarkup(<App />);

TypeError: Cannot set property 'memoizedState' of null

ps: renderToStaticMarkup can be replaced with renderToString, will be same issue
ps2: and if using useRef(renderToStaticMarkup(hello)); another error is showed Invalid hook call. Hooks can only be called...

https://codesandbox.io/s/nervous-liskov-ztt4r?file=/src/index.tsx

I'm having this issue as well using Next.js.

My experience aligns with @iamandrewluca - when using the ReactDOMServer.renderToString() method within a useMemo, I get the error: TypeError: Cannot set property 'memoizedState' of null

I can work on this task? How is the better aproach to test on code base?

I made some changes on related file of ReactPartialRendererHooks check it out 21382

@gaearon Can you help to solve some little details on the pull request process?

Is this issue is resolved. @gaearon can you confirm??
Else if not then I can take it and start from now...

I'll investigate it.

A reason

• When renderToString(), renderToStaticMarkup() is triggered, new ReactPartialRenderer is initialized.
• Hooks execute the parameter, if the parameter is a function.

Look at the code that occurs this error, the ReactPartialRenderer is already initialized to render . #16416 (comment). But useMemo Hook calls processLink() -> renderToStaticMarkup() -> another ReactPartialRenderer is initialized.
For now, those two ReactPartialRenderers are sharing the environment(closure) of ReactPartialRendererHooks.js

UseMemo - ReactFizzHooks.js

// workInProgressHook: {memoizedState : null}
const nextValue = nextCreate();
//this line calls renderToStaticMarkup() - another ReactPartialRenderer is created.

workInProgressHook.memoizedState = [nextValue, nextDeps]; // workInProgressHook is resetted. (become null)

That's why this error has occurred.

There are some ideas to resolve this issue.

1. Throw an error when the renderer is created more than one.
2. Change ReactPartialRenderHooks into class, make each ReactPartialRenderer to have a ReactPartialRenderHooks instance.
3. Create Weakmap using as a key for Component, a value for the environment. Using this environment, Remove reference of Weakmap when finishHooks() called.

@bvaughn @gaearon
If you don't mind, would you share your opinion on which one is the best? Is there a better way to handle this?

Any updates on this ticket?

Mind if I take this?

@ambar can I take up this issue if no one is working on it?

Can I take these issue, if no one is working
?

I can take a crack at this issue if nobody else has. Thanks!

@Lizzyrho21

There's been a few attempts to fix it but so far they've tried to address the symptoms rather than the root cause. I think it might be easier for me to look into this, but what would be helpful is a PR with a failing test for this issue. Would you like to create one? ReactServerRendering-test.js might be a good place to add it. Run yarn test --watch ReactServerRendering-test and try to make a test that causes this error.

@gaearon I tried to write a test but it seems it not fails in that environment. Did I miss something 🤔

it('should not crash when used inside useMemo', () => {
  function App() {
    React.useMemo(() => ReactDOMServer.renderToString(<span />), []);
    return <span />;
  }

  expect(() => ReactDOMServer.renderToString(<App />))
    .toThrowError(`Cannot set properties of null (setting 'memoizedState')`)
});

  ● ReactDOMServer › renderToString › should not crash when used inside useMemo

    expect(received).toThrowError(expected)

    Expected substring: "Cannot set properties of null (setting 'memoizedState')"

    Received function did not throw

This piece of code fails in cra browser, cra test, codesandbox and node (using createElement) with same error:

TypeError: Cannot set property 'memoizedState' of null

https://codesandbox.io/s/nervous-liskov-ztt4r?file=/src/index.tsx