Heroku build failed to compile Swift app about heroku-buildpack HOT 1 CLOSED

This is not related to Heroku or this buildpack, but the Linux compatibility of the mentioned SwiftImage package and by extension, your project.

It seems that the Image(data:) initializer that your ImageController class is using is declared with canImport guards. And since the AppKit framework does not exist on Linux, neither will the initializer, explaining the error message you got.

You will need to find another way to load image data on Linux. You will be able to iterate faster if you first try to build your project with Docker (e.g. in a throwaway container) or a Linux VM. Once the project builds there, you can resume deploying to Heroku.

I'm closing this issue since there's nothing to do from the buildpack side, but feel free to hit up the Vapor Discord server to discuss it further.

from heroku-buildpack.