Improve RSC plugin to provide better errors (#42435)
This PR improves the RSC plugin for SWC to throw an error when the `"use
client"` directive is in the top level, but not before other statements
/ expressions. For example:
Code:
```js
import 'react'
'use client'
```
Error:
```
The "use client" directive must be placed before other expressions. Move it to the top of the file to resolve this issue.
,----
3 | 'use client'
: ^^^^^^^^^^^^
`----
```
## Bug
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have a 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`
- [x] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have a helpful link attached, see `contributing.md`
## Documentation / Examples
- [ ] Make sure the linting passes by running `pnpm build && pnpm lint`
- [ ] The "examples guidelines" are followed from [our contributing
doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)
Co-authored-by: JJ Kasper <jj@jjsweb.site>
