We currently only fallback to the global `runtime` option if the page
actually **needs** a runtime (not statically optimizable). That happens
for SSG (ISR) and SSR for pages/. But for app/, we will always need a
`runtime` to render server components.
Also in this PR, I improved the tests to actually **test** the runtime
to ensure it has `globalThis.EdgeRuntime` so it's not running in the
Node.js runtime
([ref](https://edge-runtime.vercel.app/features/available-apis#addressing-the-runtime)).
## Bug
- [ ] Related issues linked using `fixes #number`
- [x] 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)
Co-authored-by: JJ Kasper <jj@jjsweb.site>
