How to install new packages when packaging a wrapper for a native package?

[D4yvid]

I'm the creator of the swift-udev library, and i published it recently to the Swift Package Index.

When SPI tried building the package, it didn't install the "libudev-dev" (Ubuntu) package on the container, resulting in build errors for every platform.

The Package.swift file specifies it as a provider for the CUDev module

The library is for linux-only, so at least the linux build should build properly

Here's the full build log:
https://swiftpackageindex.com/builds/A42A84C2-BA07-4F4C-A645-CFE74A11C183 (linux build)

I found some similar discussions about that same topic (adding system dependencies to the builder), but i didn't find a solution on them

[srivilliamsai]

Why this happens & How SPI handles system dependencies

There are two main reasons for the build failure:

1. providers: [.apt(...)] in Package.swift is only informational

In Swift Package Manager (SPM), the providers field on .systemLibrary targets is purely diagnostic metadata. SPM does not automatically run apt-get install or execute package manager commands during the build process for security and sandboxing reasons; it only uses that list to print a suggestion to the user when compilation fails.

2. SPI builder containers use a base Linux environment

The Swift Package Index (SPI) Linux builders run in standardized, isolated Docker containers containing the Swift toolchain and only a curated set of common system libraries. Because libudev-dev is not pre-installed in the base container image, the build fails when pkg-config searches for libudev.

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Recommended Solutions

1. Request the package to be added to the SPI Linux builder images (Standard Approach):
   The SPI team frequently adds common and safe system libraries (like libudev-dev, libusb-1.0-0-dev, etc.) to the builder base images. You can ask the maintainers (@daveverwer / @finestructure) here in this thread to consider adding libudev-dev to the Linux builder Docker image.

2. Restrict non-Linux platforms via .spi.yml:
   Since swift-udev is strictly Linux-only, you should add a .spi.yml file in the root of your repository so SPI only attempts Linux builds instead of failing macOS/iOS/watchOS/tvOS builds:

   version: 1
   builder:
     configs:
       - platform: linux