@types packages should be peerDependencies

[Feiyang1]

Expected Behavior / Situation

@types packages should be peerDependencies.
I'd like to enforce Node 8 support in my project, but rollup includes @types/node@12 which introduce globals/types that are only available in newer Node versions, e.g. Promise.prototype.finally.

Actual Behavior / Situation

@types packages are the direct dependency of rollup introducing undesirable global types from @types/node.

Modification Proposal

The issue is similar to #2580
You mentioned that making @types packages devDeps is not an option because rollup reexport some of those types, but you can make them peerDependencies, so the consumer has control over the version of @types packages.

If the proposal sounds reasonable to you, I will create a PR for it.

[Feiyang1]

I think long term rollup should not depend on types that define globals, e.g. @types/node, which forces consumers to include types they don't intend to include during compilation.

[lukastaegert]

The problem is that making it a peerDependency would force EVERYONE to either install them manually or have warnings during install, which is also undesired. I fear the only reasonable way to handle this that I can think of is try to get rid of this dependency altogether, not sure if this is possible in any way.

[shellscape]

We could drop that into optionalDependencies but that's a mostly declarative, symbolic move. We certainly wouldn't want to force non-TypeScript users to receive warnings during install.

[tivac]

Why is that package needed? As a non-TS user I've never understood its inclusion.

[Feiyang1]

An alternative is make a @types/rollup package and do not export types from rollup package.
People who want the types can install @types/rollup and I can work around the globals issue by not installing it.
It's also a win for non-TS user who then won't be forced to install types.

[Feiyang1]

#3131 solved my problem, but rollup regressed on 1.23.0

[lukastaegert]

Sorry, fix is upcoming

[lukastaegert]

Rollup@2 will finally fix this for good: #3395

[lukastaegert]

Solved in rollup@2.0.0