`config.experimental.serverComponents` is currently required to be
enabled or disabled together with `config.experimental.appDir` (which
means `serverComponents === appDir` otherwise it will throw) so there is
no reason to keep both of them. This PR removes `serverComponents` from
Next.js and only rely on `appDir` instead.
## 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`
- [ ] 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 lint`
- [ ] The "examples guidelines" are followed from [our contributing
doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)
Follow up for https://github.com/vercel/next.js/pull/40415
Remove internal next client api determination, fully relying on `'client'` directive.
Change `.client.js` extension to `.js ` in tests, remove legacy / unused test files
