Recently I upgraded my open source projects, including Lioness, to Swift 4.
What's somewhat special about Lioness is that it supports Linux. Which gave me a rather strange error when upgrading it to Swift 4:
swift build command is ran by Travis-CI on each commit to make sure Lioness still compiles as a Swift package on Linux.)
The weird thing is that the
swift build command worked fine with Swift 3. As I'm sure most developers would do, the first thing I tried is to Google this error. But that gave me the following disappointing result:
Appearantly no-one had ever put anything about this error on the internet. So I decided I would, with the blog post you're reading as a result.
Starting with Swift 4, it is expected that you have a
LinuxMain.swift file in the
Tests folder of your Swift package. This file is intended to include the unit tests you want to run on Linux for your Swift package. I didn't run the unit tests of Lioness on Linux at the time of writing, which is why I never bothered adding it. To be clear: the
LinuxMain.swift file may be empty, but it's required to exist if you want the Swift Package Manager commands to work.
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