[wereHamster]

To me it usually happens if I upgrade one of the @types/* packages, and then yarn/npm decides to install a separate version of its dependencies, even if I already have a different (compatible) version. There is no easy way AFAICS to tell yarn/npm that you really only want a single version of each @types/* package.

Same applies to most regular npm packages as well, for example you really only want a single version of "react", too.

[jimmyspice]

@types versioning is strange because you never know whether or not the version of the types matches the dependency exactly. for example the case where the typed version has a minor upgrade (say due to increased type coverage), the types become out of sync.

the fix is to do away with @types and export types from the dependency itself so they are always in sync

[WorldMaker]

I find after a fresh `npm install` (as opposed to `npm ci` which pays attention to package-lock.json) an `npm dedupe` almost always seems necessary. `npm install` by default still doesn't seem to work hard enough to avoid duplication, especially with @types/ packages where is often critical.

[charrondev]

Looks into the “resolutions” field for yarn. It does exactly this.