This PR fixes#30398
By default Next will polyfill some fetch APIs (Request, Response, Header and fetch) only if fetch is not found in the global scope in certain entry points. If we have a custom server which is adding a global fetch (and only fetch) at the very top then the rest of APIs will not be polyfilled.
This PR adds a test on the custom server where we can add a custom polyfill for fetch with an env variable. This reproduces the issue since next-server.js will be required without having a polyfill for Response which makes it fail on requiring NextResponse. Then we remove the code that checks for subrequests to happen within the **sandbox** so that we don't need to polyfill `next-server` anymore.
The we also introduce an improvement on how we handle relative requests. Since #31858 introduced a `port` and `hostname` options for the server, we can always pass absolute URLs to the Middleware so we can always use the original `nextUrl` to pass it to fetch. This brings a lot of simplification for `NextURL` since we don't have to consider relative URLs no more.
## Bug
- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Errors have helpful link attached, see `contributing.md`
To run middleware we are using a **sandbox** that emulates the web runtime and keeps a module cache. This cache is shared for all of the modules that we run using the sandbox while there are some module-level APIs that must be scoped depending on the module we are running.
One example of this is `fetch` where we want to always inject a special header that indicate the module that is performing the fetch and use it to avoid getting into infinite loops for middleware. For those cases the cached implementation will be the first one that instantiates the module and therefore we can actually get into infinite loops. This is the reason why #31800 is failing.
With this PR we refactor the sandbox so that the module cache is scoped per module name. This means that one execution of a middleware will preserve its cache only for that module so that each execution will still have its own `fetch` implementation, fixing this issue. Also, with this refactor the code is more clear and we also provide an option to avoid using the cache.
## 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 by running `yarn lint`
This PR removes the class wrapper that we have for `TextEncoder` and `TextDecoder`. Since this is merged we will be using directly the Node version in the sandbox.
The `resource` argument[^1] in fetch may also be an instance of URL (or any other stringifiable value) but the sandbox variant of middlewares doesn't support that.
```js
export async function middleware(req, ev) {
await fetch(new URL('https://www.googleapis.com/oauth2/v3/certs'), {
redirect: 'manual',
method: 'GET',
})
return new Response(JSON.stringify({}), { status: 200 });
}
```
This is fixing the use of e.g. URL instance in `fetch`.
```
TypeError: initurl.startsWith is not a function
at getFetchURL (/my-next-app/node_modules/next/dist/server/web/sandbox/sandbox.js:246:17)
at fetch (/my-next-app/node_modules/next/dist/server/web/sandbox/sandbox.js:77:29)
at Object.middleware [as handler] (webpack-internal:///./pages/_middleware.js:86:15)
at async adapter (webpack-internal:///./node_modules/next/dist/server/web/adapter.js:30:22)
at async DevServer.runMiddleware (/my-next-app/node_modules/next/dist/server/next-server.js:430:26)
at async DevServer.runMiddleware (/my-next-app/node_modules/next/dist/server/dev/next-dev-server.js:394:28)
at async Object.fn (/my-next-app/node_modules/next/dist/server/next-server.js:807:34)
at async Router.execute (/my-next-app/node_modules/next/dist/server/router.js:211:32)
at async DevServer.run (/my-next-app/node_modules/next/dist/server/next-server.js:1115:29)
at async DevServer.run (/my-next-app/node_modules/next/dist/server/dev/next-dev-server.js:440:20)
```
[^1]: https://developer.mozilla.org/en-US/docs/Web/API/fetch#parameters
When libraries are required outside of the middleware function context and they do checks such as `a instanceof Uint8Array` since the constructors are different between the two contexts they'll always yield false.
This is a problem for libraries validating user input as well as the WebCryptoAPI polyfill used outside of Edge Functions.
- Fixes#30477
- Fixes#30911
This is only a problem for the sandbox runtime, not when ran inside an Edge Function.
Co-authored-by: Tobias Koppers <sokra@users.noreply.github.com>
With this PR we are updating the way we check the usage of `eval` and other dynamic code evaluation (like `new Function`) for middleware. Now instead of simply showing a warning it will behave differently depending on if we are building or in development.
- Development: we replace the dynamic code with a wrapper so that we print a warning only when the code is used. We don't fail in this scenario as it is possible that once the application is built the code that uses `eval` is left out.
- Build: we detect with tree shaking if the code that will be bundled into the middleware includes any dynamic code and in such scenario we make the build fail as don't want to allow it for the production environment.
Closes#30674
## 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 by running `yarn lint`
- Code splitting should be disabled for the server-web build. Done via `ServerlessPlugin`.
- ~Target can't be `web`, `webworker` is better.~ Using `web` and `es6` for now, still not ideal.
- https://github.com/acornjs/acorn/issues/970
## Bug
- [ ] Related issues linked using `fixes #number`
- [x] 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 by running `yarn lint`
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
