This ensures we properly catch the rejection on route change failure in development so the dev overlay doesn't flash with the unhandled rejection. A test case isn't able to be added for this specific scenario as the unhandled rejection is fired right before the page is navigated so we can't consistently check if the rejection was unhandled or not.
## Bug
- [x] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`
Fixes: https://github.com/vercel/next.js/issues/28560
* Add experimental config for middleware
* Apply suggestions from code review
Co-authored-by: Steven <steven@ceriously.com>
Co-authored-by: Steven <steven@ceriously.com>
This PR adds support for [Middleware as per RFC ](https://github.com/vercel/next.js/discussions/29750).
## Feature
- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`
## Documentation / Examples
- [ ] Make sure the linting passes
This PR proposes a fix for https://github.com/vercel/next.js/issues/11107 (JS modules are loaded twice). A more detailed explanation of the investigation that led to this PR can be found in the issue's comments (https://github.com/vercel/next.js/issues/11107#issuecomment-791780168).
## Replicability
To identify that the issue replicates on any given project, you need to
1. look at the network tab (first/clean load of site, so preferably ⌘+⇧+R on an incognito tab),
2. sort by "name", and filter requests by `mime-type:application/javascript` (selecting "JS" in the devtools filters will actually show all "script" types, but ignore all "javascript" types)
3. look for pairs of identical calls with one originating from initial HTML (`preload` of priority "high" originating from "(index)" or "([page name])") and another one from a script (`prefetch` of priority "lowest" originating from a .js file), where neither of the files is served from the cache.
Here's a screenshot of an example of what to look for:
<img width="601" alt="Screen Shot 2021-03-07 at 09 59 18" src="https://user-images.githubusercontent.com/1325721/110234627-cf1c6d00-7f2b-11eb-9cd7-749bf881ba56.png">
The issue was reproduced easily on the following projects:
- On [nextjs.org](https://nextjs.org/) where duplicates add up to ~70kB of transferred javascript out of 470kB (14.9%).
- On [vercel.com](https://vercel.com/) where duplicates add up to ~105kB of transferred javascript out of 557kB (18.8%).
- On [tiktok.com](https://tiktok.com/en) where duplicates add up to ~514kB of transferred javascript out of 1556kB (33%).
- In my own project using `"next": "^10.0.1"` (private repo) where duplicates add up to about 5% of total transferred javascript.
- In the issue's comments, a developer reported a replication using `"^10.0.7"` on a [public repo](https://github.com/SidOfc/sidneyliebrand.io).
## Some information about the fix
- Both `preload` and `prefetch` values for `<link rel="x">` behave similarly, with the difference being in network priority level (preload is high priority, prefetch is lowest priority).
- Next.js uses `<link rel="preload">` in its initial HTML but then *only* uses `<link rel="prefetch">` for the rest of the lifetime of the page.
- However, when Next.js detects that a script should be requested in advance, it only checks for matching `<link rel="prefetch">` and not `<link rel="preload">` (which have higher priority and are present earlier in the DOM, thus have a greater likelihood of being already loaded).
This PR aims to fix that oversight.
## Potential issues (none AFAIK)
As far as I can tell by looking through the codebase, **there is no downside** not to add a `prefetch` when a `preload` is already in the DOM. No other script looks for a `<link>` based on its `rel` attribute.
This applies the fix from the awesome investigation done in https://github.com/vercel/next.js/issues/28797 by @jayphelps and adds a test to ensure this is working as expected. It seems that the `route-loader` has a race condition while prefetching and if a script is executed before we have created a current "future" entry to resolve the entry stays in a pending state causing routes to hang so this handles the condition by ensuring pending/errored entries do not stay around.
## Bug
- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Errors have helpful link attached, see `contributing.md`
Fixes: https://github.com/vercel/next.js/issues/28797
Fixes: https://github.com/vercel/next.js/issues/27783
The fix in PR #25749 only works some of the time. The reason why it
doesn't work all of the time is because the `devBuildResolve` function
is called when the assets have been built, but this can happen before
the `getFilesForRoute` promise chain has completed, and thus the
`cancelled` variable could not yet have been updated.
To fix this we wait for the `getFilesForRoute` promise chain to be
fulfilled and then resolve the `devBuildPromise` promise afterwards.
This allows the `getFilesForRoute` promise chain to be fulfilled before
and the `cancelled` variable can be updated accordingly.
If an error is thrown somewhere in the `getFilesForRoute` promise chain,
i.e. due to a failed fetch request, then that will also resolve the
`devBuildPromise` and the error will bubble up to ultimately become a
`routeChangeError` which will reload the page.
With this fix the need to listen for HMR events has become obsolete as
regardless of when the HMR build/sync events complete we still want to
ensure that the `getFilesForRoute` promise chain has been fulfilled
before resolving the `devBuildPromise`.
Co-authored-by: Tobias Järvelöv <tobias.jarvelov@oderland.se>
Co-authored-by: JJ Kasper <jj@jjsweb.site>
- Use SWC to compile Next.js core server files
- Ensure only @babel/runtime/helpers/interopRequireDefault helper is used
Just an initial comparison to compare size difference of this change.
## Bug
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`
## Feature
- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`
## Documentation / Examples
- [ ] Make sure the linting passes
* Prevent timeout when loading routes in development
The new route loader (https://github.com/vercel/next.js/pull/19006) will timeout
loading routes after 3.8s (MS_MAX_IDLE_DELAY), but this can easily happen when
running dev on a large app.
Fixes https://github.com/vercel/next.js/issues/25675
* Delay route loading timeout in development
* refactor: Integrate onBuildCallback into resolvePromiseWithTimeout
* refactor: Tweak for better dead-code elimination
Co-authored-by: JJ Kasper <jj@jjsweb.site>
This ensures when CSS requests stall that they are included in the route load timeout so that stalled CSS requests don't block us from falling back to a hard navigation. This handles a rare case noticed by @pacocoursey where a transition did not complete while attempting to load CSS assets.
## Bug
- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
This adds support for returning an object from `rewrites` in `next.config.js` with `beforeFiles`, `afterFiles`, and `fallback` to allow specifying rewrites at different stages of routing. The existing support for returning an array for rewrites is still supported and behaves the same way. The documentation has been updated to include information on these new stages that can be rewritten and removes the outdated note of rewrites not being able to override pages.
## Bug
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
## Feature
- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
## Documentation / Examples
- [ ] Make sure the linting passes
In the current implementation, `idleTimeout` will always be thrown even if it didn't time out and `Promise.race` was resolved. This causes the error `Error: Route did not complete loading` on every route transition and Chrome Devtools will pause code execution if you have "Pause on exceptions" enabled.
This PR adds `resolvePromiseWithTimeout` which does the same thing as `Promise.race` and `idleTimeout`, but it cancels the rejection when it resolves successfully, in which case the error won't be thrown.
Fixes#21543.
This removes `import type` usage from our core files since `import type` requires a higher TypeScript version than currently expected.
Fixes: https://github.com/vercel/next.js/issues/19300
This pull request completely replaces our old page loader with a brand new route loader.
Our existing comprehensive test suite means I did not need to add a bunch of tests. I did add them where behavior was added or fixed.
Summary of the changes:
- Eagerly evaluates prefetched pages in browser idle time (speeds up transitions)
- Router is **no longer frozen** indefinitely if the Build Manifest never arrives
- Router is **no longer frozen** indefinitely if a page fails to bootstrap
- New `withFuture` utility instead of ad-hoc deduping per resource
- Prefetching is now delayed until browser idle time to not impact TTI
- Browsers without `prefetch` now fall back to eager evaluation instead of using `preload`
- We're now ready to serve non-static assets **with `no-store` without breaking prefetching**
- **Application can now hydrate without fetching CSS assets—this is a huge performance win that was previously blocking hydration**
---
The minor size increase here is unfortunate, but we have to incur it for correctness.
---
Fixes#18389Fixes#18642