Flutter support

[mschwaig]

I tried building a flutter app with this project, which does not seem to work.

I wanted to share my notes here in case that is helpful.

I tried building https://github.com/GreenPassApp/greenpass-app as a flake with this project.

It seem like dependencies from the flutter SDK end up in the pubspec.yml like this

  flutter_web_plugins:
    dependency: transitive
    description: flutter
    source: sdk
    version: 0.0.0

while regular dependencies look like this

  app_settings:
    dependency: "direct main"
    description:
      name: app_settings
      url: "https://pub.dartlang.org"
    source: hosted
    version: "4.1.1"

The description containing text and not a name and a URL make pub2nix trip and stop adding hashes to pub2nix.lock after encountering the first such dependency.

I think pub2nix can only deal with dependencies of type hosted(the regular most common case) while the types sdk and git would probably have to be handled differently in nix-dart here and in pub2nix.

I am not sure what else would have to be done to get flutter apps building. It seems flutter would have to be invoked instead of dart.

I saw that there is also flutter support in nixpkgs (See NixOS/nixpkgs#36759 (comment)), but I have not looked more closely at that because I am unsure if there is a good way to get dependencies into a sandboxed build that way.

I am not actively working on getting this to work anymore as of now, since it was just an experiment for me. I am also not that familiar with flutter or dart.