Context

When a helper depends on another helper which is not explicitly imported (see code snippet below), the babel-plugin-transform-runtime will inject the helper at the top but it will not inject it in the proper module format version.

Let's take the possibleConstructorReturn as an example. The helper itself does not "explicitly" depend on typeof:

When building possibleConstructorReturn (build-dist#247) the babel-plugin-transform-runtime plugin will run over it and inject the unimported typeof at the very top as follows:

+ import _typeof from "@babel/runtime/helpers/typeof";
import assertThisInitialized from "./assertThisInitialized.js";

The issue is that the injected module format is CJS instead of being picked up by the context. The desired output should be the following:

- import _typeof from "@babel/runtime/helpers/typeof";
+ import _typeof from "./typeof.js";
import assertThisInitialized from "./assertThisInitialized.js";

The solution
To fix the issue I updated the adjustImportPath function to rewrite the imports generated from the babel-plugin-transform-runtime as relative path imports.

I realize that this PR is just patching the problem rather than making the transform runtime plugin import the proper module format in the first place. Doing that, however, would require us to do some rethinking of the build-dist file, which considering the issue was marked as "good first issue", I deemed it was out of scope. Let me know if I should proceed otherwise.

Testing
Guidance on testing the build-dist file is appreciated.
Updated: Commited the helper generated code to avoid regressions.