import map generation not finding package.json for some libraries like tslib (when recursively segmenting entry point)

[thescientist13]

Type of Change

Bug

Summary

Observed in AnalogStudiosRI/api#44 that Greenwood's import map generation was showing a warning that it could not find a package.json for tslib

{ segment: 'modules', resolvedPackageJson: { type: 'module' } }
recurse root {
  root: 'file:///Users/owenbuckley/Workspace/analogstudiosri/api/node_tslib/modules/'
}
 
WARNING: No supported entry point detected for => \`tslib\`

Which is odd because tslib definitely has main and module entry points defined. 🤔

Details

After a little debugging, the issue is in the naivety of our logic that recursively walks up from the entry point to the first valid package.json as it slowly trims the path as it walks up

root = root.replace(`${segment}/`, '');

The issue here is the tslib package has a directory called modules, so as we can see in the logs above, node_modules was getting string replaced instead of at the end of the path.

Doing this seems to work

root = root.substring(0, root.lastIndexOf(segment));