Resolved package.json does not reflect resolved file

[wbinnssmith]

Consider the following tree:

foo/
  package.json {sideEffects: false}
  real-bar.js
  bar/
    package.json {main: '../real-bar.js', has no defined sideEffects property}

Intuitively, it seems that real-bar.js's sideEffects value should be false, not undefined, as it's a child of the foo directory, which has a package.json defining "sideEffects": false.

However, when import 'foo/bar' is currently resolved, it resolves correctly to foo/real-bar.js, but the associated package.json for the asset is foo/bar/package.json, not foo/package.json. This makes foo/real-bar.js's sideEffects value undefined when it's required as import 'foo/bar', but it's false when it's required as import 'foo/real-bar.js' (or import './real-bar.js' or similar).

We should consider conditionally re-resolving an asset's package.json when the initially resolved package.json points to a module that would otherwise resolve a different package.json.

cc @mischnic @devongovett @thebriando

[mischnic]

I think the proposed way makes sense, in any case we should do what the other tools do