config.build should be inheritable

[threepointone]

config.build should be inheritable/redefinable across environments (which makes sense, because builds/build commands are typically different across environments; different vars, params, etc.). I think wrangler1 supports this.

This is a bit tricky because this might imply that main/rules should be inheritable. Maybe it should be. But it would be nice if this combination would work:

• top level main
• top level build
• env specific build (that outputs to top level main)
• and optionally env specific main

I spent a few minutes on this but got confused, so I'm filing this issue instead for now.

• feat: make main an inheritable environment field #650
• fix: allow the build field to be inherited/overridden in a named environment #673
• fix: tighten up the named environment configuration #668

[petebacondarwin]

I think making main an inheritable field makes sense. Even without a custom build I could imagine having:

src/
  index.dev.ts
  index.prod.ts

where various env specific constants etc could be defined.

[petebacondarwin]

And we have already agreed for rules to be inheritable:

https://github.com/cloudflare/wrangler2/blob/6b44822b1742e2b84e6b38c383e78043db922b67/packages/wrangler/src/config/environment.ts#L126-L134

We have deprecated the rules that existed in the upload field:

https://github.com/cloudflare/wrangler2/blob/6b44822b1742e2b84e6b38c383e78043db922b67/packages/wrangler/src/config/config.ts#L261-L265

Although I note in the code, we are just grabbing the rules from the top-level environment and ignoring the current environment. I think this might be a problem across the codebase for other properties; or at least it is a potential foot-gun.
So I will put together a PR to make it more easy to do the right thing.