Makes it possible to switch between edge/server runtime in dev without
breaking the server.
Fixes slack:
[1](https://vercel.slack.com/archives/CGU8HUTUH/p1659082535540549)
[2](https://vercel.slack.com/archives/C02CDC2ALJH/p1658978287244359)
[3](https://vercel.slack.com/archives/C03KAR5DCKC/p1656869427468779)
#### middleware-plugin.ts
`middlewareManifest` moved from module scope to local scope. Stale state
from earlier builds ended up in `middleware-manifest.json`. Functions
that changed from edge to server runtime stayed in the manifest as edge
functions.
#### on-demand-entry-handler.ts
When a server or edge entry is added we check if it has switched
runtime. If that's the case the old entry is removed.
#### Reproduce
Create edge API route and visit `/api/hello`
```js
// pages/api/hello.js
export const config = {
runtime: 'experimental-edge',
}
export default () => new Response('Hello')
```
Change it to a server api route and visit `/api/hello`, it will explode.
```js
// pages/api/hello.js
export default function (req, res) {
res.send('Hello')
}
```
#### Bug not fixed
One EDGE case is not fixed. It occurs if you switch between edge and
server runtime several times without changing the content of the file:
Edge runtime
```js
export const config = {
runtime: 'experimental-edge',
}
export default () => new Response('Hello')
```
Change it to a server runtime
```js
export default function (req, res) {
res.send('Hello')
}
```
Change back to edge runtime, the content of the file is the same as the
first time we compiled the edge runtime version.
```js
export const config = {
runtime: 'experimental-edge',
}
export default () => new Response('Hello')
```
The reason is that both the edge and server compiler emits to the same
file (/.next/server/pages/api/hello.js) which makes this check fail in
webpack:
https://github.com/webpack/webpack/blob/main/lib/Compiler.js#L849-L861
Possible solution is to use different output folders for edge and server
https://vercel.slack.com/archives/CGU8HUTUH/p1661163106667559
Co-authored-by: JJ Kasper <jj@jjsweb.site>
a9b9e00703