fixes #4108 Forum returns 404 for correct links

[IlyaSmiyukha]

fixes #4108

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[thesan]

@IlyaSmiyukha to QA this and simulate the QN going down without needing to run a local network I used FoxyProxy.

But the page still redirect to a 404 instead of showing an unending loading screen or an error message. Which would both be an improvement on the current behavior:

Peek.2023-04-07.16-59.webm

[IlyaSmiyukha]

Will check it

[IlyaSmiyukha]

@thesan

I made a fix for handling errors for threads. Right now it shows an infinity loader. We can change it to an error message like this. But I need a text for the message.

[thesan]

The loader would be a good option if Apollo was re-trying on error which doesn't seem to be the case (maybe there is a setting for it).

Alternatively could we have something like:
"Something went wrong fetching this thread: {Error message returned by the QN}"

WDYT @dmtrjsg ?

[thesan]

@IlyaSmiyukha I don't think this change is right. AFAIK isRefetched is just supposed to indicate that the data was already fetched once. So once it has been set to true it should remain this way. Or am I missing something ?

[IlyaSmiyukha]

For the current post you are right, But when the user opens another post isRefetched will return true. And in this case he will be redirected to 404 page. So when the URL was changed we should update isRefetched as well

[thesan]

I see... But the problem with this solution is that: in places where deps is undefined (which is most places the hook is used), the useEffect is re-rendered periodically. As a result isRefetched becomes false periodically.

isRefetched was introduced in #3359 to prevent the loading screen to reappear when re-fetching data. So setting to false at the wrong time will cause this issue.

Here whether this issue will happen depends on whether the data are re-fetched due to a re-render or the interval and the re-render + the time it takes to actually re-fetch the data. Which makes the behavior of this hook hard to predict.

For example when testing while simulating the QN being down it happened for me on the main forum page:

Peek.2023-04-14.10-32.webm

The page only flickers because the request fails quickly.

So this solution should be improved a bit. However I wasn't able to reproduce the case you described. Here's my attempt:

Peek.2023-04-14.11-15.webm

In my understanding when the URL is changed the hook is unmounted and remounted so isRefetched is reset to false.

Or am I testing the wrong case ?

[dmtrjsg]

@thesan sounds good 👍

[IlyaSmiyukha]

I pushed changes. It will say: Something went wrong fetching this thread. Otherwise, it will look a bit ugly with {an Error message returned by the QN}. Something went wrong fetching this thread: Error: failed to fetch

[thesan]

@IlyaSmiyukha

[thesan]

I see... But the problem with this solution is that: in places where deps is undefined (which is most places the hook is used), the useEffect is re-rendered periodically. As a result isRefetched becomes false periodically.

isRefetched was introduced in #3359 to prevent the loading screen to reappear when re-fetching data. So setting to false at the wrong time will cause this issue.

Here whether this issue will happen depends on whether the data are re-fetched due to a re-render or the interval and the re-render + the time it takes to actually re-fetch the data. Which makes the behavior of this hook hard to predict.

For example when testing while simulating the QN being down it happened for me on the main forum page:

Peek.2023-04-14.10-32.webm

The page only flickers because the request fails quickly.

So this solution should be improved a bit. However I wasn't able to reproduce the case you described. Here's my attempt:

Peek.2023-04-14.11-15.webm

In my understanding when the URL is changed the hook is unmounted and remounted so isRefetched is reset to false.

Or am I testing the wrong case ?

[IlyaSmiyukha]

@thesan
I will recheck it one more time

[IlyaSmiyukha]

Screen.Recording.2023-04-15.at.11.25.13.mov

@thesan
Pay attention pls to the console log. I removed the fix and print what return refetched on the page change. It should return false, but the hook still returns true. If be honest not sure why.

[thesan]

Hey @IlyaSmiyukha you were right there was a lot going wrong with the query refetching: First the isRefetched was set to true before it got fetched in the first place, second there is no GetForumThreads query on this page and finally the posts should be polled not the thread itself. Also the useRefetchQueries is called almost everywhere without dependencies, which works but is bad for performances, but then I think that's the intended behavior in some places, so it shouldn't be changed everywhere blindly.

Since there was a lot to fix I committed the fixes directly on this PR. Hopefully it doesn't break other component using the same hook 🤞

Good job catching the bug here 🙌

@chrlschwb could someone give this PR one last review before I merge it please? Just in case I missed something in the code I wrote.

[IlyaSmiyukha]

It's great! Thanks @thesan

[chrlschwb]

All the stuff you mentioned are in the code.