We currently have inconsistencies when working with URLs in the Edge Functions runtime, this PR addresses them introducing a warning for inconsistent usage that will break in the future. Here is the reasoning.
### The Browser
When we are in a browser environment there is a fixed location stored at `globalThis.location`. Then, if one tries to build a request with a relative URL it will work using that location global hostname as _base_ to construct its URL. For example:
```typescript
// https://nextjs.org
new Request('/test').url; // https://nextjs.org/test
Response.redirect('/test').headers.get('Location'); // https://nextjs.org/test
```
However, if we attempt to run the same code from `about:blank` it would not work because the global to use as a base `String(globalThis.location)` is not a valid URL. Therefore a call to `Response.redirect('/test')` or `new Response('/test')` would fail.
### Edge Functions Runtime
In Next.js Edge Functions runtime the situation is slightly different from a browser. Say that we have a root middleware (`pages/_middleware`) that gets invoked for every page. In the middleware file we expose the handler function and also define a global variable that we mutate on every request:
```typescript
// pages/_middleware
let count = 0;
export function middleware(req: NextRequest) {
console.log(req.url);
count += 1;
}
```
Currently we cache the module scope in the runtime so subsequent invocations would hold the same globals and the module would not be evaluated again. This would make the counter to increment for each request that the middleware handles. It is for this reason that we **can't have a global location** that changes across different invocations. Each invocation of the same function uses the same global which also holds primitives like `URL` or `Request` so changing an hypothetical `globalThis.location` per request would affect concurrent requests being handled.
Then, it is not possible to use relative URLs in the same way the browser does because we don't have a global to rely on to use its host to compose a URL from a relative path.
### Why it works today
We are **not** validating what is provided to, for example, `NextResponse.rewrite()` nor `NextResponse.redirect()`. We simply create a `Response` instance that adds the corresponding header for the rewrite or the redirect. Then it is **the consumer** the one that composes the final destination based on the request. Theoretically you can pass any value and it would fail on redirect but won't validate the input.
Of course this is inconsistent because it doesn't make sense that `NextResponse.rewrite('/test')` works but `fetch(new NextRequest('/test'))` does not. Also we should validate what is provided. Finally, we want to be consistent with the way a browser behaves so `new Request('/test')` _should_ not work if there is no global location which we lack.
### What this PR does
We will have to deprecate the usage of relative URLs in the previously mentioned scenarios. In preparation for it, this PR adds a validation function in those places where it will break in the future, printing a warning with a link that points to a Next.js page with an explanation of the issue and ways to fix it.
Although middleware changes are not covered by semver, we will roll this for some time to make people aware that this change is coming. Then after a reasonable period of time we can remove the warning and make the code fail when using relative URLs in the previously exposed scenarios.
* JSON.stringify generic errors
* Add util for normalizing errors
* lint-fix
* Add better error for null case as well
Co-authored-by: Michael Ozeryansky <mozeryansky@users.noreply.github.com>
fixes#31520
## Bug
- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] 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 by running `yarn lint`
This adds an error document/link for hydration errors to help users debug these easier. While looking at adding this also noticed a typo in the dev-overlay which is fixed.
<details>
<summary>screenshot</summary>
<img width="1109" alt="Screen Shot 2021-11-16 at 15 56 29" src="https://user-images.githubusercontent.com/22380829/142078200-6c036ed9-ca7f-4d26-ae07-eb9bd89e991a.png">
</details>
## Documentation / Examples
- [x] Make sure the linting passes by running `yarn lint`
Co-authored-by: Tim Neutkens <6324199+timneutkens@users.noreply.github.com>
Links the failed to load bindings error document to the new discussion here: https://github.com/vercel/next.js/discussions/30468
## Documentation / Examples
- [x] Make sure the linting passes by running `yarn lint`
In #29010, we started throwing an error if the res was mutated after
getServerSideProps() returned. This was to support classic streaming,
where it would be possible to accidentally mutate the response headers
after they were already sent. However, this change also caught [a few
non-streaming cases](https://github.com/vercel/next.js/pull/29010#issuecomment-943482743) that we don't want to break.
As such, with this change, we only throw the error if res is mutated
after gSSP returns *and* you've opted into using classic streaming.
Otherwise, we will only add a warning to the console.
* Add deprecation note for target
* Apply suggestions from code review
Co-authored-by: Steven <steven@ceriously.com>
* Mention Vercel leverages the traces
Co-authored-by: Steven <steven@ceriously.com>
`?` is any optional character, it isn't the same as the `?` in regex which will match the preceding character 0 or more times.
## 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
- [x] Make sure the linting passes
* Throw error if res is accessed after gSSP returns
Currently it's possible to access the `ServerResponse` through `context.res`
in `getServerSideProps()`. If one was to store that response and mutate
its headers or status code after gSSP returns (e.g. during rendering), it
would currently happen to work because of when headers are sent. However,
this is an anti-pattern that relies an implementation detail of the framework
and shouldn't be allowed. This will be particularly important once Next.js
starts to support basic streaming (two-part flush: routing then data) because
then the headers will be sent as soon as gSSP returns, which explicitly breaks
this pattern.
With this commit, the framework now throws an error in development mode if
the ServerResponse is accessed after gSSP returns.
* fixup! Throw error if res is accessed after gSSP returns
This ensures we handle 204 and 304 status codes correctly in API routes.
## 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/28464
This adds a new ESLint rule to `eslint-plugin-next` to check that `next/script` components with inline content have the required `id` attribute.
Also adjusted the code example for inline scripts in the `next/script` docs, which were actually missing an `id` attribute.
And also updated the `next/scripts` integration test to also have the required `id` attribute.
Unsure about the required heading levels in the errors .md document (other examples have h1 and h4??)
## 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
- [x] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [x] Errors have helpful link attached, see `contributing.md`
## Documentation / Examples
- [ ] Make sure the linting passes
This PR adds documentation for the new `rootDir` setting (#27918), and for `next/no-html-link-for-pages`.
## Documentation / Examples
- [x] Make sure the linting passes
