I think there are a few other things which continue to affect Swift's adoption outside of Apple platforms:
- Lack of online and downloadable documentation, similar to swiftdocs.org. That would include whatever's generated from the header docs as well as long form documentation, available in a variety of formats (Dash docset?), and including the ability to see documentation for released versions as well as
master, and perhaps other branches. Built in API diffing would be great too. - Lack of a centralized and searchable package database with full SPM (and Xcode!) integration, similar to CocoaPods. Users must be able to find Swift packages and easily integrate them. Going as far as CocoaPods does and offering the ability to fully render documentation, showing testing levels, and other info would also be great.
- More officially supported platforms that are well maintained, as it's not enough that the language builds on a platform. Swift is still a pain to build on Linux, and even the official Ubuntu support hasn't expanded above 16.10. I should be able to easily install Swift from any major package manager without having to manually include dependencies. I am glad there's a semi-official Docker image though.
Without these things, Swift's adoption outside Apple's platforms will be limited to those already familiar with Swift wanting to use it on some other platform.