I'm trying to create a package that works across Flutter, Web, and Other on pub.dart.org. As long as the default file in the package does not have platform dependencies, other files can do so without causing the whole package to be platform dependent. This works when one file uses dart:io and another uses dart:html, as long as the default import does not do that.
However, adding any sort of dependency on Flutter, say because there's a single file in the package that uses it, causes pub.dart.org to list the package as Flutter only.
I believe it has something to do with the fact Flutter actually requires an SDK in pubspec.yaml, but I haven't been able to find any further information about this.