In development with a custom server, cache page loads if page contents didn't change

[kanjieater]

Feature request

Is your feature request related to a problem? Please describe.

I'm using a custom express server inside an electron app. When I load the electron app I see

[elec] > Using external babel configuration
[elec] > Location: "/app/babel.config.js"
[elec] [ ready ] compiled successfully
[elec] [ event ] build page: /
[elec] [ wait ]  compiling ...
[elec] [ ready ] compiled successfully

When I make a change to any file in the electron app (for example in the main process, which kicks off the server), the app restarts (with electron-reload), and it boots up the custom server again. I then see the exact same output.

If the server is restarted, Next.js is recompiling pages unnecessarily.

Describe the solution you'd like

Only compile pages if something relating to the server has changed, not on every restart of the server.

Describe alternatives you've considered

None are apparent to me currently, but I'm open to ideas.

Additional context

Reproduction steps:

1. Start a custom server
2. Let it build some page.
3. Shut the server down with something like Ctrl^C
4. Restart it
5. Wait for it to build again, despite no code being changed.