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Lazy compilation can fail when switching "routes" quickly #15541
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do you using |
No, I don't think so. You can see the full webpack config SB generates with |
OK, I simplified the repro a lot and brought it out of Storybook! https://github.com/tmeasday/webpack-lazy-compilation-repro-simple
The content of window.all = async () => {
import('./a');
await new Promise((r) => setTimeout(r, 0));
import('./b');
await new Promise((r) => setTimeout(r, 0));
import('./c');
}; Interestingly the issue doesn't occur if you remove the final call to |
@tmeasday still does not work with latest webpack? |
|
@vankop I am not quite sure what happened 6 days ago in my comment directly above, but I came back to this today and tried it again, and it the reproduction I posted definitely does occur in It is a pretty simple reproduction so hopefully it should make the problem clear :) |
@vankop I dug into this a bit and I think I have some more context on what is going wrong here, in case it helps. Apologies in advance for my lack of understanding of how HMR stuff works in detail. So, just to reiterate, what's happening in the failing repro above is that we are Actually the issue can happen even when even importing two files with a delay, but it doesn't happen every time. It's interesting to see what happen when it does work vs when it does. When the lazy compilation works, on the terminal (with all logging turned on), I see:
Notice in particular the two messages The two modules do not actually get "used" at the same time, there is a 2ms gap between them, but for whatever reason the new compilation triggered by the invalidate hasn't actually started yet. On the client, on the HMR socket we see a really straightforward set of messages for a single HMR update and it all works fine: When it doesn't work, it is because the compilation starts before the second invalidation:
In this case, notice the "Compilation starting..." message is logged before the "...b.js is now in use and will be compiled." message. Ultimately this leads to the following messages over the websocket: (Here's where I get a bit more hazy) -- what this means is that there are actually two "changes" in compilation -- we go from an initial hash, to a second hash with I am not sure exactly what the root problem is. I suspect that maybe the lazy compilation backend shouldn't (or shouldn't be able to) invalidate the compilation while it is compiling. Perhaps somewhere in the pipeline there should be a queue of invalidations that blocks on previous compilations? |
@vankop FYI I implemented a workaround on SB's end by putting some pipelining/throttling in our client side code to avoid overlapping To be clear, I don't think this is a great solution because I wonder if the right solution is to add a similar throttle to this I tried it out and it did resolve the problem, although I did need to put a little delay in (>10ms <100ms) between one compilation finishing and the next one starting (I think because otherwise the HMR update gets invalidated before the browser has a chance to grab it, although I didn't dig in too much). I'm really unsure if this is the right approach or not (plus how I'd go about adding a test to webpack for it). |
This issue had no activity for at least three months. It's subject to automatic issue closing if there is no activity in the next 15 days. |
Issue was closed because of inactivity. If you think this is still a valid issue, please file a new issue with additional information. |
As a note we are still working around this problem in Storybook in a way which probably isn't ideal for performance: https://github.com/storybookjs/storybook/blob/15dd0ad6891e964f807a22e3e3827c0e7f599a1b/code/lib/core-webpack/src/to-importFn.ts#L50-L55 |
@tmeasday Something which I am still facing too in my repo. Issue: storybookjs/storybook#22706
scrollstorybook.mov |
Bug report
What is the current behavior?
When using the experimental lazy compilation feature (in Storybook), when you change stories quickly (thus triggering many different lazy compilation jobs), sometimes the HMR for the lazy update can fail in various ways, which can lead to
react-refresh
errors or simply the whole app having to reload itself.If the current behavior is a bug, please provide the steps to reproduce.
It is not entirely predictable, and I have not managed to reproduce outside of Storybook (yet), but this is a very very simple Storybook project and I think it is quite obvious the bug is in Webpack, but I am ready to be corrected ;)
https://github.com/tmeasday/storybook-lazy-compilation-webpack -- see the instructions from the repo.
The key point in this reproduction is that when a bunch of lazy updates are created on the server, the browser, which is otherwise doing nothing, will sometimes 404 on a
hot-update.json
request:Note we have seen other (less reproducible) issues around HMR and lazy compilation, that you might see if you play with this repository, including:
rm -rf node_modules/.cache/ && yarn storybook
and let the browser launch).option-down
andoption-up
to do this). However I cannot make this happen reliably enough to create a reproduction that would be useful. If you'd like to see what I mean I can likely get a screen recording of it happening at least.What is the expected behavior?
Lazy compilation should be fairly transparent to the consumer, beyond
import()
requests taking a little longer than they otherwise might. If updates come over the wire from compilations triggered by other browsers, they should not fail.Other relevant information:
webpack version: 5.70.0
Node.js version: 14.18.1
Operating System: MacOS
Additional tools: Storybook 6.5.0-alpha.48
NOTE
The tool we are using here to trigger the bug is the Storybook test runner, which opens the Storybook up in 4 separate, concurrent playwright instances, each of which will trigger a different dynamic (and thus lazy-compiled)
import()
statement.The text was updated successfully, but these errors were encountered: