preserveEntrySignatures: exports-only

[guybedford]

Feature Use Case

preserveEntrySignatures is a really nice API for selecting when facades are really needed (and it turns out not so much!).

But turning on 'allow-extension' might still cause issues for some facades where the exact names might be needed.

Feature Proposal

The proposal is for an exports-only setting, which would effectively follow 'strict' for all entry modules that have exports, but set it to 'allow-extension' for all entry modules that have any exports.

This way the top-level "exportless" entry point always gets collapsed, but we avoid risk for other types of chunks.

[lukastaegert]

Sounds sensible and could be a good default for the next major version. Thus we could also avoid the ugly warning you get when an entry point has no exports.

[lukastaegert]

I created a PR for this because I think it will be a good default for the next major version of Rollup: #3823.

but we avoid risk for other types of chunks.

Note that the preserveSignatures option only every had an effect on static entry points anyway. Dynamic entry points and internal namespace imports always have their signature preserved as Rollup will just create a namespace object if the signature would be polluted: https://rollupjs.org/repl/?version=2.31.0&shareable=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